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authorAnton Vorontsov <anton.vorontsov@linaro.org>2012-05-31 16:26:24 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-05-31 17:49:30 -0700
commitaf1be5a578a1ccc9961c55290f8c509a00a69036 (patch)
treef8659ba36228582a114c7809bdf580640eb626cf /arch
parent2214f707de257c35773d5cd68cec9e31b91e01ca (diff)
downloadlinux-af1be5a578a1ccc9961c55290f8c509a00a69036.tar.gz
blackfin: fix possible deadlock in decode_address()
Oleg Nesterov found an interesting deadlock possibility: > sysrq_showregs_othercpus() does smp_call_function(showacpu) > and showacpu() show_stack()->decode_address(). Now suppose that IPI > interrupts the task holding read_lock(tasklist). To fix this, blackfin should not grab the write_ variant of the tasklist lock, read_ one is enough. Suggested-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org> Cc: Mike Frysinger <vapier@gentoo.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/blackfin/kernel/trace.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/arch/blackfin/kernel/trace.c b/arch/blackfin/kernel/trace.c
index d08f0e3e2dc..f7f7a18abca 100644
--- a/arch/blackfin/kernel/trace.c
+++ b/arch/blackfin/kernel/trace.c
@@ -29,7 +29,7 @@ void decode_address(char *buf, unsigned long address)
{
struct task_struct *p;
struct mm_struct *mm;
- unsigned long flags, offset;
+ unsigned long offset;
struct rb_node *n;
#ifdef CONFIG_KALLSYMS
@@ -113,7 +113,7 @@ void decode_address(char *buf, unsigned long address)
* mappings of all our processes and see if we can't be a whee
* bit more specific
*/
- write_lock_irqsave(&tasklist_lock, flags);
+ read_lock(&tasklist_lock);
for_each_process(p) {
struct task_struct *t;
@@ -186,7 +186,7 @@ __continue:
sprintf(buf, "/* kernel dynamic memory */");
done:
- write_unlock_irqrestore(&tasklist_lock, flags);
+ read_unlock(&tasklist_lock);
}
#define EXPAND_LEN ((1 << CONFIG_DEBUG_BFIN_HWTRACE_EXPAND_LEN) * 256 - 1)