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2013-04-30workqueue: include workqueue info when printing debug dump of a worker taskTejun Heo
One of the problems that arise when converting dedicated custom threadpool to workqueue is that the shared worker pool used by workqueue anonimizes each worker making it more difficult to identify what the worker was doing on which target from the output of sysrq-t or debug dump from oops, BUG() and friends. This patch implements set_worker_desc() which can be called from any workqueue work function to set its description. When the worker task is dumped for whatever reason - sysrq-t, WARN, BUG, oops, lockdep assertion and so on - the description will be printed out together with the workqueue name and the worker function pointer. The printing side is implemented by print_worker_info() which is called from functions in task dump paths - sched_show_task() and dump_stack_print_info(). print_worker_info() can be safely called on any task in any state as long as the task struct itself is accessible. It uses probe_*() functions to access worker fields. It may print garbage if something went very wrong, but it wouldn't cause (another) oops. The description is currently limited to 24bytes including the terminating \0. worker->desc_valid and workder->desc[] are added and the 64 bytes marker which was already incorrect before adding the new fields is moved to the correct position. Here's an example dump with writeback updated to set the bdi name as worker desc. Hardware name: Bochs Modules linked in: Pid: 7, comm: kworker/u9:0 Not tainted 3.9.0-rc1-work+ #1 Workqueue: writeback bdi_writeback_workfn (flush-8:0) ffffffff820a3ab0 ffff88000f6e9cb8 ffffffff81c61845 ffff88000f6e9cf8 ffffffff8108f50f 0000000000000000 0000000000000000 ffff88000cde16b0 ffff88000cde1aa8 ffff88001ee19240 ffff88000f6e9fd8 ffff88000f6e9d08 Call Trace: [<ffffffff81c61845>] dump_stack+0x19/0x1b [<ffffffff8108f50f>] warn_slowpath_common+0x7f/0xc0 [<ffffffff8108f56a>] warn_slowpath_null+0x1a/0x20 [<ffffffff81200150>] bdi_writeback_workfn+0x2a0/0x3b0 ... Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@redhat.com> Acked-by: Jan Kara <jack@suse.cz> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Dave Chinner <david@fromorbit.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-04-30dump_stack: unify debug information printed by show_regs()Tejun Heo
show_regs() is inherently arch-dependent but it does make sense to print generic debug information and some archs already do albeit in slightly different forms. This patch introduces a generic function to print debug information from show_regs() so that different archs print out the same information and it's much easier to modify what's printed. show_regs_print_info() prints out the same debug info as dump_stack() does plus task and thread_info pointers. * Archs which didn't print debug info now do. alpha, arc, blackfin, c6x, cris, frv, h8300, hexagon, ia64, m32r, metag, microblaze, mn10300, openrisc, parisc, score, sh64, sparc, um, xtensa * Already prints debug info. Replaced with show_regs_print_info(). The printed information is superset of what used to be there. arm, arm64, avr32, mips, powerpc, sh32, tile, unicore32, x86 * s390 is special in that it used to print arch-specific information along with generic debug info. Heiko and Martin think that the arch-specific extra isn't worth keeping s390 specfic implementation. Converted to use the generic version. Note that now all archs print the debug info before actual register dumps. An example BUG() dump follows. kernel BUG at /work/os/work/kernel/workqueue.c:4841! invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC Modules linked in: CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.9.0-rc1-work+ #7 Hardware name: empty empty/S3992, BIOS 080011 10/26/2007 task: ffff88007c85e040 ti: ffff88007c860000 task.ti: ffff88007c860000 RIP: 0010:[<ffffffff8234a07e>] [<ffffffff8234a07e>] init_workqueues+0x4/0x6 RSP: 0000:ffff88007c861ec8 EFLAGS: 00010246 RAX: ffff88007c861fd8 RBX: ffffffff824466a8 RCX: 0000000000000001 RDX: 0000000000000046 RSI: 0000000000000001 RDI: ffffffff8234a07a RBP: ffff88007c861ec8 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000000 R12: ffffffff8234a07a R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff88007dc00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b CR2: ffff88015f7ff000 CR3: 00000000021f1000 CR4: 00000000000007f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Stack: ffff88007c861ef8 ffffffff81000312 ffffffff824466a8 ffff88007c85e650 0000000000000003 0000000000000000 ffff88007c861f38 ffffffff82335e5d ffff88007c862080 ffffffff8223d8c0 ffff88007c862080 ffffffff81c47760 Call Trace: [<ffffffff81000312>] do_one_initcall+0x122/0x170 [<ffffffff82335e5d>] kernel_init_freeable+0x9b/0x1c8 [<ffffffff81c47760>] ? rest_init+0x140/0x140 [<ffffffff81c4776e>] kernel_init+0xe/0xf0 [<ffffffff81c6be9c>] ret_from_fork+0x7c/0xb0 [<ffffffff81c47760>] ? rest_init+0x140/0x140 ... v2: Typo fix in x86-32. v3: CPU number dropped from show_regs_print_info() as dump_stack_print_info() has been updated to print it. s390 specific implementation dropped as requested by s390 maintainers. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: David S. Miller <davem@davemloft.net> Acked-by: Jesper Nilsson <jesper.nilsson@axis.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Bjorn Helgaas <bhelgaas@google.com> Cc: Fengguang Wu <fengguang.wu@intel.com> Cc: Mike Frysinger <vapier@gentoo.org> Cc: Vineet Gupta <vgupta@synopsys.com> Cc: Sam Ravnborg <sam@ravnborg.org> Acked-by: Chris Metcalf <cmetcalf@tilera.com> [tile bits] Acked-by: Richard Kuo <rkuo@codeaurora.org> [hexagon bits] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-04-30dump_stack: implement arch-specific hardware description in task dumpsTejun Heo
x86 and ia64 can acquire extra hardware identification information from DMI and print it along with task dumps; however, the usage isn't consistent. * x86 show_regs() collects vendor, product and board strings and print them out with PID, comm and utsname. Some of the information is printed again later in the same dump. * warn_slowpath_common() explicitly accesses the DMI board and prints it out with "Hardware name:" label. This applies to both x86 and ia64 but is irrelevant on all other archs. * ia64 doesn't show DMI information on other non-WARN dumps. This patch introduces arch-specific hardware description used by dump_stack(). It can be set by calling dump_stack_set_arch_desc() during boot and, if exists, printed out in a separate line with "Hardware name:" label. dmi_set_dump_stack_arch_desc() is added which sets arch-specific description from DMI data. It uses dmi_ids_string[] which is set from dmi_present() used for DMI debug message. It is superset of the information x86 show_regs() is using. The function is called from x86 and ia64 boot code right after dmi_scan_machine(). This makes the explicit DMI handling in warn_slowpath_common() unnecessary. Removed. show_regs() isn't yet converted to use generic debug information printing and this patch doesn't remove the duplicate DMI handling in x86 show_regs(). The next patch will unify show_regs() handling and remove the duplication. An example WARN dump follows. WARNING: at kernel/workqueue.c:4841 init_workqueues+0x35/0x505() Modules linked in: CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.9.0-rc1-work+ #3 Hardware name: empty empty/S3992, BIOS 080011 10/26/2007 0000000000000009 ffff88007c861e08 ffffffff81c614dc ffff88007c861e48 ffffffff8108f500 ffffffff82228240 0000000000000040 ffffffff8234a08e 0000000000000000 0000000000000000 0000000000000000 ffff88007c861e58 Call Trace: [<ffffffff81c614dc>] dump_stack+0x19/0x1b [<ffffffff8108f500>] warn_slowpath_common+0x70/0xa0 [<ffffffff8108f54a>] warn_slowpath_null+0x1a/0x20 [<ffffffff8234a0c3>] init_workqueues+0x35/0x505 ... v2: Use the same string as the debug message from dmi_present() which also contains BIOS information. Move hardware name into its own line as warn_slowpath_common() did. This change was suggested by Bjorn Helgaas. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Bjorn Helgaas <bhelgaas@google.com> Cc: David S. Miller <davem@davemloft.net> Cc: Fengguang Wu <fengguang.wu@intel.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Jesper Nilsson <jesper.nilsson@axis.com> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Mike Frysinger <vapier@gentoo.org> Cc: Vineet Gupta <vgupta@synopsys.com> Cc: Sam Ravnborg <sam@ravnborg.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-04-30dump_stack: consolidate dump_stack() implementations and unify their behaviorsTejun Heo
Both dump_stack() and show_stack() are currently implemented by each architecture. show_stack(NULL, NULL) dumps the backtrace for the current task as does dump_stack(). On some archs, dump_stack() prints extra information - pid, utsname and so on - in addition to the backtrace while the two are identical on other archs. The usages in arch-independent code of the two functions indicate show_stack(NULL, NULL) should print out bare backtrace while dump_stack() is used for debugging purposes when something went wrong, so it does make sense to print additional information on the task which triggered dump_stack(). There's no reason to require archs to implement two separate but mostly identical functions. It leads to unnecessary subtle information. This patch expands the dummy fallback dump_stack() implementation in lib/dump_stack.c such that it prints out debug information (taken from x86) and invokes show_stack(NULL, NULL) and drops arch-specific dump_stack() implementations in all archs except blackfin. Blackfin's dump_stack() does something wonky that I don't understand. Debug information can be printed separately by calling dump_stack_print_info() so that arch-specific dump_stack() implementation can still emit the same debug information. This is used in blackfin. This patch brings the following behavior changes. * On some archs, an extra level in backtrace for show_stack() could be printed. This is because the top frame was determined in dump_stack() on those archs while generic dump_stack() can't do that reliably. It can be compensated by inlining dump_stack() but not sure whether that'd be necessary. * Most archs didn't use to print debug info on dump_stack(). They do now. An example WARN dump follows. WARNING: at kernel/workqueue.c:4841 init_workqueues+0x35/0x505() Hardware name: empty Modules linked in: CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.9.0-rc1-work+ #9 0000000000000009 ffff88007c861e08 ffffffff81c614dc ffff88007c861e48 ffffffff8108f50f ffffffff82228240 0000000000000040 ffffffff8234a03c 0000000000000000 0000000000000000 0000000000000000 ffff88007c861e58 Call Trace: [<ffffffff81c614dc>] dump_stack+0x19/0x1b [<ffffffff8108f50f>] warn_slowpath_common+0x7f/0xc0 [<ffffffff8108f56a>] warn_slowpath_null+0x1a/0x20 [<ffffffff8234a071>] init_workqueues+0x35/0x505 ... v2: CPU number added to the generic debug info as requested by s390 folks and dropped the s390 specific dump_stack(). This loses %ksp from the debug message which the maintainers think isn't important enough to keep the s390-specific dump_stack() implementation. dump_stack_print_info() is moved to kernel/printk.c from lib/dump_stack.c. Because linkage is per objecct file, dump_stack_print_info() living in the same lib file as generic dump_stack() means that archs which implement custom dump_stack() - at this point, only blackfin - can't use dump_stack_print_info() as that will bring in the generic version of dump_stack() too. v1 The v1 patch broke build on blackfin due to this issue. The build breakage was reported by Fengguang Wu. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: David S. Miller <davem@davemloft.net> Acked-by: Vineet Gupta <vgupta@synopsys.com> Acked-by: Jesper Nilsson <jesper.nilsson@axis.com> Acked-by: Vineet Gupta <vgupta@synopsys.com> Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com> [s390 bits] Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Mike Frysinger <vapier@gentoo.org> Cc: Fengguang Wu <fengguang.wu@intel.com> Cc: Bjorn Helgaas <bhelgaas@google.com> Cc: Sam Ravnborg <sam@ravnborg.org> Acked-by: Richard Kuo <rkuo@codeaurora.org> [hexagon bits] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-04-29printk: fix failure to return error in devkmsg_poll()Nicolas Kaiser
Error value got overwritten instantly. Signed-off-by: Nicolas Kaiser <nikai@nikai.net> Cc: Kay Sievers <kay.sievers@vrfy.org> Cc: Greg KH <greg@kroah.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-04-29early_printk: consolidate random copies of identical codeThomas Gleixner
The early console implementations are the same all over the place. Move the print function to kernel/printk and get rid of the copies. [akpm@linux-foundation.org: arch/mips/kernel/early_printk.c needs kernel.h for va_list] [paul.gortmaker@windriver.com: sh4: make the bios early console support depend on EARLY_PRINTK] Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Russell King <linux@arm.linux.org.uk> Acked-by: Mike Frysinger <vapier@gentoo.org> Cc: Michal Simek <monstr@monstr.eu> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mundt <lethal@linux-sh.org> Cc: "David S. Miller" <davem@davemloft.net> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Richard Weinberger <richard@nod.at> Reviewed-by: Ingo Molnar <mingo@kernel.org> Tested-by: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-04-29printk/tracing: rework console tracingzhangwei(Jovi)
Commit 7ff9554bb578 ("printk: convert byte-buffer to variable-length record buffer") removed start and end parameters from call_console_drivers, but those parameters still exist in include/trace/events/printk.h. Without start and end parameters handling, printk tracing became more simple as: trace_console(text, len); Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@huawei.com> Acked-by: Steven Rostedt <rostedt@goodmis.org> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Kay Sievers <kay@vrfy.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-03-22printk: Provide a wake_up_klogd() off-caseFrederic Weisbecker
wake_up_klogd() is useless when CONFIG_PRINTK=n because neither printk() nor printk_sched() are in use and there are actually no waiter on log_wait waitqueue. It should be a stub in this case for users like bust_spinlocks(). Otherwise this results in this warning when CONFIG_PRINTK=n and CONFIG_IRQ_WORK=n: kernel/built-in.o In function `wake_up_klogd': (.text.wake_up_klogd+0xb4): undefined reference to `irq_work_queue' To fix this, provide an off-case for wake_up_klogd() when CONFIG_PRINTK=n. There is much more from console_unlock() and other console related code in printk.c that should be moved under CONFIG_PRINTK. But for now, focus on a minimal fix as we passed the merged window already. [akpm@linux-foundation.org: include printk.h in bust_spinlocks.c] Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Reported-by: James Hogan <james.hogan@imgtec.com> Cc: James Hogan <james.hogan@imgtec.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-02-25Merge branch 'drm-next' of git://people.freedesktop.org/~airlied/linuxLinus Torvalds
Pull drm merge from Dave Airlie: "Highlights: - TI LCD controller KMS driver - TI OMAP KMS driver merged from staging - drop gma500 stub driver - the fbcon locking fixes - the vgacon dirty like zebra fix. - open firmware videomode and hdmi common code helpers - major locking rework for kms object handling - pageflip/cursor won't block on polling anymore! - fbcon helper and prime helper cleanups - i915: all over the map, haswell power well enhancements, valleyview macro horrors cleaned up, killing lots of legacy GTT code, - radeon: CS ioctl unification, deprecated UMS support, gpu reset rework, VM fixes - nouveau: reworked thermal code, external dp/tmds encoder support (anx9805), fences sleep instead of polling, - exynos: all over the driver fixes." Lovely conflict in radeon/evergreen_cs.c between commit de0babd60d8d ("drm/radeon: enforce use of radeon_get_ib_value when reading user cmd") and the new changes that modified that evergreen_dma_cs_parse() function. * 'drm-next' of git://people.freedesktop.org/~airlied/linux: (508 commits) drm/tilcdc: only build on arm drm/i915: Revert hdmi HDP pin checks drm/tegra: Add list of framebuffers to debugfs drm/tegra: Fix color expansion drm/tegra: Split DC_CMD_STATE_CONTROL register write drm/tegra: Implement page-flipping support drm/tegra: Implement VBLANK support drm/tegra: Implement .mode_set_base() drm/tegra: Add plane support drm/tegra: Remove bogus tegra_framebuffer structure drm: Add consistency check for page-flipping drm/radeon: Use generic HDMI infoframe helpers drm/tegra: Use generic HDMI infoframe helpers drm: Add EDID helper documentation drm: Add HDMI infoframe helpers video: Add generic HDMI infoframe helpers drm: Add some missing forward declarations drm: Move mode tables to drm_edid.c drm: Remove duplicate drm_mode_cea_vic() gma500: Fix n, m1 and m2 clock limits for sdvo and lvds ...
2013-02-19Merge branch 'irq-core-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull irq core changes from Ingo Molnar: "The biggest changes are the IRQ-work and printk changes from Frederic Weisbecker, which prepare the code for 'full dynticks' (the ability to stop or slow down the periodic tick arbitrarily, not just in idle time as today): - Don't stop tick with irq works pending. This fix is generally useful and concerns archs that can't raise self IPIs. - Flush irq works before CPU offlining. - Introduce "lazy" irq works that can wait for the next tick to be executed, unless it's stopped. - Implement klogd wake up using irq work. This removes the ad-hoc printk_tick()/printk_needs_cpu() hooks and make it working even in dynticks mode. - Cleanups and fixes." * 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: genirq: Export enable/disable_percpu_irq() arch Kconfig: Remove references to IRQ_PER_CPU irq_work: Remove return value from the irq_work_queue() function genirq: Avoid deadlock in spurious handling printk: Wake up klogd using irq_work irq_work: Make self-IPIs optable irq_work: Warn if there's still work on cpu_down irq_work: Flush work on CPU_DYING irq_work: Don't stop the tick with pending works nohz: Add API to check tick state irq_work: Remove CONFIG_HAVE_IRQ_WORK irq_work: Fix racy check on work pending flag irq_work: Fix racy IRQ_WORK_BUSY flag setting
2013-02-05Merge branch 'nohz/printk-v8' into irq/coreFrederic Weisbecker
Conflicts: kernel/irq_work.c Add support for printk in full dynticks CPU. * Don't stop tick with irq works pending. This fix is generally useful and concerns archs that can't raise self IPIs. * Flush irq works before CPU offlining. * Introduce "lazy" irq works that can wait for the next tick to be executed, unless it's stopped. * Implement klogd wake up using irq work. This removes the ad-hoc printk_tick()/printk_needs_cpu() hooks and make it working even in dynticks mode. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
2013-01-31Revert "console: implement lockdep support for console_lock"Dave Airlie
This reverts commit daee779718a319ff9f83e1ba3339334ac650bb22. I'll requeue this after the console locking fixes, so lockdep is useful again for people until fbcon is fixed. Signed-off-by: Dave Airlie <airlied@redhat.com>
2013-01-04printk: fix incorrect length from print_time() when seconds > 99999Roland Dreier
print_prefix() passes a NULL buf to print_time() to get the length of the time prefix; when printk times are enabled, the current code just returns the constant 15, which matches the format "[%5lu.%06lu] " used to print the time value. However, this is obviously incorrect when the whole seconds part of the time gets beyond 5 digits (100000 seconds is a bit more than a day of uptime). The simple fix is to use snprintf(NULL, 0, ...) to calculate the actual length of the time prefix. This could be micro-optimized but it seems better to have simpler, more readable code here. The bug leads to the syslog system call miscomputing which messages fit into the userspace buffer. If there are enough messages to fill log_buf_len and some have a timestamp >= 100000, dmesg may fail with: # dmesg klogctl: Bad address When this happens, strace shows that the failure is indeed EFAULT due to the kernel mistakenly accessing past the end of dmesg's buffer, since dmesg asks the kernel how big a buffer it needs, allocates a bit more, and then gets an error when it asks the kernel to fill it: syslog(0xa, 0, 0) = 1048576 mmap(NULL, 1052672, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fa4d25d2000 syslog(0x3, 0x7fa4d25d2010, 0x100008) = -1 EFAULT (Bad address) As far as I can see, the bug has been there as long as print_time(), which comes from commit 084681d14e42 ("printk: flush continuation lines immediately to console") in 3.5-rc5. Signed-off-by: Roland Dreier <roland@purestorage.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Joe Perches <joe@perches.com> Cc: Sylvain Munaut <s.munaut@whatever-company.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-12-17printk: boot_delay should only affect outputAndrew Cooks
The boot_delay parameter affects all printk(), even if the log level prevents visible output from the call. It results in delays greater than the user intended without purpose. This patch changes the behaviour of boot_delay to only delay output. Signed-off-by: Andrew Cooks <acooks@gmail.com> Acked-by: Randy Dunlap <rdunlap@infradead.org> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-11-18printk: Wake up klogd using irq_workFrederic Weisbecker
klogd is woken up asynchronously from the tick in order to do it safely. However if printk is called when the tick is stopped, the reader won't be woken up until the next interrupt, which might not fire for a while. As a result, the user may miss some message. To fix this, lets implement the printk tick using a lazy irq work. This subsystem takes care of the timer tick state and can fix up accordingly. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Acked-by: Steven Rostedt <rostedt@goodmis.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
2012-10-23console: use might_sleep in console_lockDaniel Vetter
Instead of BUG_ON(in_interrupt()), since that doesn't check for all the newfangled stuff like preempt. Note that this is valid since the console_sem is essentially used like a real mutex with only two twists: - we allow trylock from hardirq context - across suspend/resume we lock the logical console_lock, but drop the semaphore protecting the locking state. Now that doesn't guarantee that no one is playing tricks in single-thread atomic contexts at suspend/resume/boot time, but - I couldn't find anything suspicious with some grepping, - might_sleep shouldn't die, - and I think the upside of catching more potential issues is worth the risk of getting a might_sleep backtrace that would have been save (and then dealing with that fallout). Cc: Dave Airlie <airlied@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-10-22console: implement lockdep support for console_lockDaniel Vetter
Dave Airlie recently discovered a locking bug in the fbcon layer, where a timer_del_sync (for the blinking cursor) deadlocks with the timer itself, since both (want to) hold the console_lock: https://lkml.org/lkml/2012/8/21/36 Unfortunately the console_lock isn't a plain mutex and hence has no lockdep support. Which resulted in a few days wasted of tracking down this bug (complicated by the fact that printk doesn't show anything when the console is locked) instead of noticing the bug much earlier with the lockdep splat. Hence I've figured I need to fix that for the next deadlock involving console_lock - and with kms/drm growing ever more complex locking that'll eventually happen. Now the console_lock has rather funky semantics, so after a quick irc discussion with Thomas Gleixner and Dave Airlie I've quickly ditched the original idead of switching to a real mutex (since it won't work) and instead opted to annotate the console_lock with lockdep information manually. There are a few special cases: - The console_lock state is protected by the console_sem, and usually grabbed/dropped at _lock/_unlock time. But the suspend/resume code drops the semaphore without dropping the console_lock (see suspend_console/resume_console). But since the same thread that did the suspend will do the resume, we don't need to fix up anything. - In the printk code there's a special trylock, only used to kick off the logbuffer printk'ing in console_unlock. But all that happens while lockdep is disable (since printk does a few other evil tricks). So no issue there, either. - The console_lock can also be acquired form irq context (but only with a trylock). lockdep already handles that. This all leaves us with annotating the normal console_lock, _unlock and _trylock functions. And yes, it works - simply unloading a drm kms driver resulted in lockdep complaining about the deadlock in fbcon_deinit: ====================================================== [ INFO: possible circular locking dependency detected ] 3.6.0-rc2+ #552 Not tainted ------------------------------------------------------- kms-reload/3577 is trying to acquire lock: ((&info->queue)){+.+...}, at: [<ffffffff81058c70>] wait_on_work+0x0/0xa7 but task is already holding lock: (console_lock){+.+.+.}, at: [<ffffffff81264686>] bind_con_driver+0x38/0x263 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (console_lock){+.+.+.}: [<ffffffff81087440>] lock_acquire+0x95/0x105 [<ffffffff81040190>] console_lock+0x59/0x5b [<ffffffff81209cb6>] fb_flashcursor+0x2e/0x12c [<ffffffff81057c3e>] process_one_work+0x1d9/0x3b4 [<ffffffff810584a2>] worker_thread+0x1a7/0x24b [<ffffffff8105ca29>] kthread+0x7f/0x87 [<ffffffff813b1204>] kernel_thread_helper+0x4/0x10 -> #0 ((&info->queue)){+.+...}: [<ffffffff81086cb3>] __lock_acquire+0x999/0xcf6 [<ffffffff81087440>] lock_acquire+0x95/0x105 [<ffffffff81058cab>] wait_on_work+0x3b/0xa7 [<ffffffff81058dd6>] __cancel_work_timer+0xbf/0x102 [<ffffffff81058e33>] cancel_work_sync+0xb/0xd [<ffffffff8120a3b3>] fbcon_deinit+0x11c/0x1dc [<ffffffff81264793>] bind_con_driver+0x145/0x263 [<ffffffff81264a45>] unbind_con_driver+0x14f/0x195 [<ffffffff8126540c>] store_bind+0x1ad/0x1c1 [<ffffffff8127cbb7>] dev_attr_store+0x13/0x1f [<ffffffff8116d884>] sysfs_write_file+0xe9/0x121 [<ffffffff811145b2>] vfs_write+0x9b/0xfd [<ffffffff811147b7>] sys_write+0x3e/0x6b [<ffffffff813b0039>] system_call_fastpath+0x16/0x1b other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(console_lock); lock((&info->queue)); lock(console_lock); lock((&info->queue)); *** DEADLOCK *** v2: Mark the lockdep_map static, noticed by Jani Nikula. Cc: Dave Airlie <airlied@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-10-16printk: Fix scheduling-while-atomic problem in console_cpu_notify()Paul E. McKenney
The console_cpu_notify() function runs with interrupts disabled in the CPU_DYING case. It therefore cannot block, for example, as will happen when it calls console_lock(). Therefore, remove the CPU_DYING leg of the switch statement to avoid this problem. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-08-12printk: Fix calculation of length used to discard recordsJeff Mahoney
While tracking down a weird buffer overflow issue in a program that looked to be sane, I started double checking the length returned by syslog(SYSLOG_ACTION_READ_ALL, ...) to make sure it wasn't overflowing the buffer. Sure enough, it was. I saw this in strace: 11339 syslog(SYSLOG_ACTION_READ_ALL, "<5>[244017.708129] REISERFS (dev"..., 8192) = 8279 It turns out that the loops that calculate how much space the entries will take when they're copied don't include the newlines and prefixes that will be included in the final output since prev flags is passed as zero. This patch properly accounts for it and fixes the overflow. CC: stable@kernel.org Signed-off-by: Jeff Mahoney <jeffm@suse.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-07-30printk: only look for prefix levels in kernel messagesJoe Perches
vprintk_emit() prefix parsing should only be done for internal kernel messages. This allows existing behavior to be kept in all cases. Signed-off-by: Joe Perches <joe@perches.com> Cc: Kay Sievers <kay@vrfy.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-07-30printk: add generic functions to find KERN_<LEVEL> headersJoe Perches
The current form of a KERN_<LEVEL> is "<.>". Add printk_get_level and printk_skip_level functions to handle these formats. These functions centralize tests of KERN_<LEVEL> so a future modification can change the KERN_<LEVEL> style and shorten the number of bytes consumed by these headers. [akpm@linux-foundation.org: fix build error and warning] Signed-off-by: Joe Perches <joe@perches.com> Cc: Kay Sievers <kay.sievers@vrfy.org> Cc: Wu Fengguang <wfg@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-07-30kmsg: /dev/kmsg - properly return possible copy_from_user() failureKay Sievers
Reported-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-07-26Merge tag 'driver-core-3.6-rc1' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core Pull driver core changes from Greg Kroah-Hartman: "Here's the big driver core pull request for 3.6-rc1. Unlike 3.5, this kernel should be a lot tamer, with the printk changes now settled down. All we have here is some extcon driver updates, w1 driver updates, a few printk cleanups that weren't needed for 3.5, but are good to have now, and some other minor fixes/changes in the driver core. All of these have been in the linux-next releases for a while now. Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>" * tag 'driver-core-3.6-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core: (38 commits) printk: Export struct log size and member offsets through vmcoreinfo Drivers: hv: Change the hex constant to a decimal constant driver core: don't trigger uevent after failure extcon: MAX77693: Add extcon-max77693 driver to support Maxim MAX77693 MUIC device sysfs: fail dentry revalidation after namespace change fix sysfs: fail dentry revalidation after namespace change extcon: spelling of detach in function doc extcon: arizona: Stop microphone detection if we give up on it extcon: arizona: Update cable reporting calls and split headset PM / Runtime: Do not increment device usage counts before probing kmsg - do not flush partial lines when the console is busy kmsg - export "continuation record" flag to /dev/kmsg kmsg - avoid warning for CONFIG_PRINTK=n compilations kmsg - properly print over-long continuation lines driver-core: Use kobj_to_dev instead of re-implementing it driver-core: Move kobj_to_dev from genhd.h to device.h driver core: Move deferred devices to the end of dpm_list before probing driver core: move uevent call to driver_register driver core: fix shutdown races with probe/remove(v3) Extcon: Arizona: Add driver for Wolfson Arizona class devices ...
2012-07-21printk: Implement some unlocked kmsg_dump functionsAnton Vorontsov
If used from KDB, the locked variants are prone to deadlocks (suppose we got to the debugger w/ the logbuf lock held). So, we have to implement a few routines that grab no logbuf lock. Yet we don't need these functions in modules, so we don't export them. Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-07-21printk: Remove kdb_syslog_dataAnton Vorontsov
The function is no longer needed, so remove it. Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-07-19printk: Export struct log size and member offsets through vmcoreinfoVivek Goyal
There are tools like makedumpfile and vmcore-dmesg which can extract kernel log buffer from vmcore. Since we introduced structured logging, that functionality is broken. Now user space tools need to know about "struct log" and offsets of various fields to be able to parse struct log data and extract text message or dictonary. This patch exports some of the fields. Currently I am not exporting log "level" info as that is a bitfield and offsetof() bitfields can't be calculated. But if people start asking for log level info in the output then we probably either need to seprate out "level" or use bit shift operations for flags and level. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Acked-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-07-16kmsg - do not flush partial lines when the console is busyKay Sievers
Fragments of continuation lines are flushed to the console immediately. In case the console is locked, the fragment must be queued up in the cont buffer. If the the console is busy and the continuation line is complete, but no part of it was written to the console up to this point, we can just store the entire line as a regular record and free the buffer earlier. If the console is busy and earlier messages are already queued up, we should not flush the fragments of continuation lines, but store them after the queued up messages, to ensure the proper ordering. This keeps the console output better readable in case printk()s race against each other, or we receive over-long continuation lines we need to flush. Signed-off-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-07-16kmsg - export "continuation record" flag to /dev/kmsgKay Sievers
In some cases we are forced to store individual records for a continuation line print. Export a flag to allow the external re-construction of the line. The flag allows us to apply a similar logic externally which is used internally when the console, /proc/kmsg or the syslog() output is printed. $ cat /dev/kmsg 4,165,0,-;Free swap = 0kB 4,166,0,-;Total swap = 0kB 6,167,0,c;[ 4,168,0,+;0 4,169,0,+;1 4,170,0,+;2 4,171,0,+;3 4,172,0,+;] 6,173,0,-;[0 1 2 3 ] 6,174,0,-;Console: colour VGA+ 80x25 6,175,0,-;console [tty0] enabled Signed-off-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-07-16kmsg - avoid warning for CONFIG_PRINTK=n compilationsKay Sievers
Signed-off-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-07-16kmsg - properly print over-long continuation linesKay Sievers
Reserve PREFIX_MAX bytes in the LOG_LINE_MAX line when buffering a continuation line, to be able to properly prefix the LOG_LINE_MAX line with the syslog prefix and timestamp when printing it. Reported-By: Dave Jones <davej@redhat.com> Signed-off-by: Kay Sievers <kay@vrfy.org> Cc: stable <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-07-09kmsg: merge continuation records while printingKay Sievers
In (the unlikely) case our continuation merge buffer is busy, we unfortunately can not merge further continuation printk()s into a single record and have to store them separately, which leads to split-up output of these lines when they are printed. Add some flags about newlines and prefix existence to these records and try to reconstruct the full line again, when the separated records are printed. Reported-By: Michael Neuling <mikey@neuling.org> Cc: Dave Jones <davej@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Tested-By: Michael Neuling <mikey@neuling.org> Signed-off-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-07-09kmsg: /proc/kmsg - support reading of partial log recordsKay Sievers
Restore support for partial reads of any size on /proc/kmsg, in case the supplied read buffer is smaller than the record size. Some people seem to think is is ia good idea to run: $ dd if=/proc/kmsg bs=1 of=... as a klog bridge. Resolves-bug: https://bugzilla.kernel.org/show_bug.cgi?id=44211 Reported-by: Jukka Ollila <jiiksteri@gmail.com> Signed-off-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-07-06kmsg: make sure all messages reach a newly registered boot consoleKay Sievers
We suppress printing kmsg records to the console, which are already printed immediately while we have received their fragments. Newly registered boot consoles print the entire kmsg buffer during registration. Clear the console-suppress flag after we skipped the record during its first storage, so any later print will see these records as usual. Signed-off-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-07-06kmsg: properly handle concurrent non-blocking read() from /proc/kmsgKay Sievers
The /proc/kmsg read() interface is internally simply wired up to a sequence of syslog() syscalls, which might are racy between their checks and actions, regarding concurrency. In the (very uncommon) case of concurrent readers of /dev/kmsg, relying on usual O_NONBLOCK behavior, the recently introduced mutex might block an O_NONBLOCK reader in read(), when poll() returns for it, but another process has already read the data in the meantime. We've seen that while running artificial test setups and tools that "fight" about /proc/kmsg data. This restores the original /proc/kmsg behavior, where in case of concurrent read()s, poll() might wake up but the read() syscall will just return 0 to the caller, while another process has "stolen" the data. This is in the general case not the expected behavior, but it is the exact same one, that can easily be triggered with a 3.4 kernel, and some tools might just rely on it. The mutex is not needed, the original integrity issue which introduced it, is in the meantime covered by: "fill buffer with more than a single message for SYSLOG_ACTION_READ" 116e90b23f74d303e8d607c7a7d54f60f14ab9f2 Cc: Yuanhan Liu <yuanhan.liu@linux.intel.com> Acked-by: Jan Beulich <jbeulich@suse.com> Signed-off-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-07-06kmsg: add the facility number to the syslog prefixKay Sievers
After the recent split of facility and level into separate variables, we miss the facility value (always 0 for kernel-originated messages) in the syslog prefix. On Tue, Jul 3, 2012 at 12:45 PM, Dan Carpenter <dan.carpenter@oracle.com> wrote: > Static checkers complain about the impossible condition here. > > In 084681d14e ('printk: flush continuation lines immediately to > console'), we changed msg->level from being a u16 to being an unsigned > 3 bit bitfield. Cc: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-07-06kmsg: escape the backslash character while exporting dataKay Sievers
Non-printable characters in the log data are hex-escaped to ensure safe post processing. We need to escape a backslash we find in the data, to be able to distinguish it from a backslash we add for the escaping. Also escape the non-printable character 127. Thanks to Miloslav Trmac for the heads up. Reported-by: Michael Neuling <mikey@neuling.org> Signed-off-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-07-06printk: replacing the raw_spin_lock/unlock with raw_spin_lock/unlock_irqliu chuansheng
In function devkmsg_read/writev/llseek/poll/open()..., the function raw_spin_lock/unlock is used, there is potential deadlock case happening. CPU1: thread1 doing the cat /dev/kmsg: raw_spin_lock(&logbuf_lock); while (user->seq == log_next_seq) { when thread1 run here, at this time one interrupt is coming on CPU1 and running based on this thread,if the interrupt handle called the printk which need the logbuf_lock spin also, it will cause deadlock. So we should use raw_spin_lock/unlock_irq here. Acked-by: Kay Sievers <kay@vrfy.org> Signed-off-by: liu chuansheng <chuansheng.liu@intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-06-30printk.c: fix kernel-doc warningsRandy Dunlap
Fix kernel-doc warnings in printk.c: use correct parameter name. Warning(kernel/printk.c:2429): No description found for parameter 'buf' Warning(kernel/printk.c:2429): Excess function parameter 'line' description in 'kmsg_dump_get_buffer' Signed-off-by: Randy Dunlap <rdunlap@xenotime.net> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-06-29printk: Optimize if statement logic where newline existsSteven Rostedt
In reviewing Kay's fix up patch: "printk: Have printk() never buffer its data", I found two if statements that could be combined and optimized. Put together the two 'cont.len && cont.owner == current' if statements into a single one, and check if we need to call cont_add(). This also removes the unneeded double cont_flush() calls. Link: http://lkml.kernel.org/r/1340869133.876.10.camel@mop Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Cc: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-06-29printk: flush continuation lines immediately to consoleKay Sievers
Continuation lines are buffered internally, intended to merge the chunked printk()s into a single record, and to isolate potentially racy continuation users from usual terminated line users. This though, has the effect that partial lines are not printed to the console in the moment they are emitted. In case the kernel crashes in the meantime, the potentially interesting printed information would never reach the consoles. Here we share the continuation buffer with the console copy logic, and partial lines are always immediately flushed to the available consoles. They are still buffered internally to improve the readability and integrity of the messages and minimize the amount of needed record headers to store. Signed-off-by: Kay Sievers <kay@vrfy.org> Tested-by: Steven Rostedt <rostedt@goodmis.org> Acked-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-06-26syslog: fill buffer with more than a single message for SYSLOG_ACTION_READJan Beulich
The recent changes to the printk buffer management resulted in SYSLOG_ACTION_READ to only return a single message, whereas previously the buffer would get filled as much as possible. As, when too small to fit everything, filling it to the last byte would be pretty ugly with the new code, the patch arranges for as many messages as possible to get returned in a single invocation. User space tools in at least all SLES versions depend on the old behavior. This at once addresses the issue attempted to get fixed with commit b56a39ac263e5b8cafedd551a49c2105e68b98c2 ("printk: return -EINVAL if the message len is bigger than the buf size"), and since that commit widened the possibility for losing a message altogether, the patch here assumes that this other commit would get reverted first (otherwise the patch here won't apply). Furthermore, this patch also addresses the problem dealt with in commit 4a77a5a06ec66ed05199b301e7c25f42f979afdc ("printk: use mutex lock to stop syslog_seq from going wild"), so I'd recommend reverting that one too (albeit there's no direct collision between the two). Signed-off-by: Jan Beulich <jbeulich@suse.com> Acked-by: Kay Sievers <kay@vrfy.org> Cc: Yuanhan Liu <yuanhan.liu@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-06-26Revert "printk: return -EINVAL if the message len is bigger than the buf size"Greg Kroah-Hartman
This reverts commit b56a39ac263e5b8cafedd551a49c2105e68b98c2. A better patch from Jan will follow this to resolve the issue. Acked-by: Kay Sievers <kay@vrfy.org> Cc: Fengguang Wu <wfg@linux.intel.com> Cc: Yuanhan Liu <yuanhan.liu@linux.intel.com> Cc: Jan Beulich <JBeulich@suse.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-06-25printk: fix regression in SYSLOG_ACTION_CLEARAlan Stern
Commit 7ff9554bb578ba02166071d2d487b7fc7d860d62 (printk: convert byte-buffer to variable-length record buffer) introduced a regression by accidentally removing a "break" statement from inside the big switch in printk's do_syslog(). The symptom of this bug is that the "dmesg -C" command doesn't only clear the kernel's log buffer; it also disables console logging. This patch (as1561) fixes the regression by adding the missing "break". Signed-off-by: Alan Stern <stern@rowland.harvard.edu> CC: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-06-16printk: return -EINVAL if the message len is bigger than the buf sizeYuanhan Liu
Just like what devkmsg_read() does, return -EINVAL if the message len is bigger than the buf size, or it will trigger a segfault error. Acked-by: Kay Sievers <kay@vrfy.org> Acked-by: Fengguang Wu <wfg@linux.intel.com> Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-06-16printk: use mutex lock to stop syslog_seq from going wildYuanhan Liu
Although syslog_seq and log_next_seq stuff are protected by logbuf_lock spin log, it's not enough. Say we have two processes A and B, and let syslog_seq = N, while log_next_seq = N + 1, and the two processes both come to syslog_print at almost the same time. And No matter which process get the spin lock first, it will increase syslog_seq by one, then release spin lock; thus later, another process increase syslog_seq by one again. In this case, syslog_seq is bigger than syslog_next_seq. And latter, it would make: wait_event_interruptiable(log_wait, syslog != log_next_seq) don't wait any more even there is no new write comes. Thus it introduce a infinite loop reading. I can easily see this kind of issue by the following steps: # cat /proc/kmsg # at meantime, I don't kill rsyslog # So they are the two processes. # xinit # I added drm.debug=6 in the kernel parameter line, # so that it will produce lots of message and let that # issue happen It's 100% reproducable on my side. And my disk will be filled up by /var/log/messages in a quite short time. So, introduce a mutex_lock to stop syslog_seq from going wild just like what devkmsg_read() does. It does fix this issue as expected. v2: use mutex_lock_interruptiable() instead (comments from Kay) Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com> Reviewed-by: Fengguang Wu <fengguang.wu@intel.com> Acked-By: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-06-15kmsg - kmsg_dump() use iterator to receive log buffer contentKay Sievers
Provide an iterator to receive the log buffer content, and convert all kmsg_dump() users to it. The structured data in the kmsg buffer now contains binary data, which should no longer be copied verbatim to the kmsg_dump() users. The iterator should provide reliable access to the buffer data, and also supports proper log line-aware chunking of data while iterating. Signed-off-by: Kay Sievers <kay@vrfy.org> Tested-by: Tony Luck <tony.luck@intel.com> Reported-by: Anton Vorontsov <anton.vorontsov@linaro.org> Tested-by: Anton Vorontsov <anton.vorontsov@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-06-12printk: Fix alignment of buf causing crash on ARM EABIAndrew Lunn
Commit 7ff9554bb578ba02166071d2d487b7fc7d860d62, printk: convert byte-buffer to variable-length record buffer, causes systems using EABI to crash very early in the boot cycle. The first entry in struct log is a u64, which for EABI must be 8 byte aligned. Make use of __alignof__() so the compiler to decide the alignment, but allow it to be overridden using CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS, for systems which can perform unaligned access and want to save a few bytes of space. Tested on Orion5x and Kirkwood. Signed-off-by: Andrew Lunn <andrew@lunn.ch> Tested-by: Stephen Warren <swarren@wwwdotorg.org> Acked-by: Stephen Warren <swarren@wwwdotorg.org> Acked-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-05-14printk() - isolate KERN_CONT users from ordinary complete linesKay Sievers
Arrange the continuation printk() buffering to be fully separated from the ordinary full line users. Limit the exposure to races and wrong printk() line merges to users of continuation only. Ordinary full line users racing against continuation users will no longer affect each other. Multiple continuation users from different threads, racing against each other will not wrongly be merged into a single line, but printed as separate lines. Test output of a kernel module which starts two separate threads which race against each other, one of them printing a single full terminated line: printk("(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)\n"); The other one printing the line, every character separate in a continuation loop: printk("(C"); for (i = 0; i < 58; i++) printk(KERN_CONT "C"); printk(KERN_CONT "C)\n"); Behavior of single and non-thread-aware printk() buffer: # modprobe printk-race printk test init (CC(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) C(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) CC(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) C(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) CC(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) C(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) C(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) CC(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) C(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) C(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC) (CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC) New behavior with separate and thread-aware continuation buffer: # modprobe printk-race printk test init (AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) (AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) (AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) (CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC) (AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) (AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) (AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) (AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) (CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC) (CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC) Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Joe Perches <joe@perches.com> Cc: Ted Ts'o <tytso@mit.edu> Cc: Ingo Molnar <mingo@kernel.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Sasha Levin <levinsasha928@gmail.com> Signed-off-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-05-14printk() - restore prefix/timestamp printing for multi-newline stringsKay Sievers
Calls like: printk("\n *** DEADLOCK ***\n\n"); will print 3 properly indented, separated, syslog + timestamp prefixed lines in the log output. Reported-By: Sasha Levin <levinsasha928@gmail.com> Signed-off-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-05-11printk: add stub for prepend_timestamp()Randy Dunlap
Add a stub for prepend_timestamp() when CONFIG_PRINTK is not enabled. Fixes this build error: kernel/printk.c:1770:3: error: implicit declaration of function 'prepend_timestamp' Cc: Kay Sievers <kay@vrfy.org> Signed-off-by: Randy Dunlap <rdunlap@xenotime.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>