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authorJason Baron <jbaron@redhat.com>2011-10-04 14:13:19 -0700
committerGreg Kroah-Hartman <gregkh@suse.de>2011-10-18 11:22:00 -0700
commit431625dac14de7152235f2f9934d70a9b0f9df83 (patch)
tree8c08388a455e5fba84596f90942c756765967b47 /lib
parentbd22c01e845ad22a89ae25005b38d28e6690c27a (diff)
downloadlinux-431625dac14de7152235f2f9934d70a9b0f9df83.tar.gz
dynamic_debug: use a single printk() to emit messages
We were using KERN_CONT to combine messages with their prefix. However, KERN_CONT is not smp safe, in the sense that it can interleave messages. This interleaving can result in printks coming out at the wrong loglevel. With the high frequency of printks that dynamic debug can produce this is not desirable. So make dynamic_emit_prefix() fill a char buf[64] instead of doing a printk directly. If we enable printing out of function, module, line, or pid info, they are placed in this 64 byte buffer. In my testing 64 bytes was enough size to fulfill all requests. Even if it's not, we can match up the printk itself to see where it's from, so to me this is no big deal. [akpm@linux-foundation.org: convert dangerous macro to C] Signed-off-by: Jason Baron <jbaron@redhat.com> Cc: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Andrew Morton <akpm@google.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'lib')
-rw-r--r--lib/dynamic_debug.c80
1 files changed, 41 insertions, 39 deletions
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 198d2afe18e..edec7805233 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -422,52 +422,60 @@ static int ddebug_exec_query(char *query_string)
return 0;
}
-static int dynamic_emit_prefix(const struct _ddebug *descriptor)
+#define PREFIX_SIZE 64
+
+static int remaining(int wrote)
+{
+ if (PREFIX_SIZE - wrote > 0)
+ return PREFIX_SIZE - wrote;
+ return 0;
+}
+
+static char *dynamic_emit_prefix(const struct _ddebug *desc, char *buf)
{
- char tid[sizeof(int) + sizeof(int)/2 + 4];
- char lineno[sizeof(int) + sizeof(int)/2];
+ int pos_after_tid;
+ int pos = 0;
- if (descriptor->flags & _DPRINTK_FLAGS_INCL_TID) {
+ pos += snprintf(buf + pos, remaining(pos), "%s", KERN_DEBUG);
+ if (desc->flags & _DPRINTK_FLAGS_INCL_TID) {
if (in_interrupt())
- snprintf(tid, sizeof(tid), "%s", "<intr> ");
+ pos += snprintf(buf + pos, remaining(pos), "%s ",
+ "<intr>");
else
- snprintf(tid, sizeof(tid), "[%d] ",
- task_pid_vnr(current));
- } else {
- tid[0] = 0;
+ pos += snprintf(buf + pos, remaining(pos), "[%d] ",
+ task_pid_vnr(current));
}
+ pos_after_tid = pos;
+ if (desc->flags & _DPRINTK_FLAGS_INCL_MODNAME)
+ pos += snprintf(buf + pos, remaining(pos), "%s:",
+ desc->modname);
+ if (desc->flags & _DPRINTK_FLAGS_INCL_FUNCNAME)
+ pos += snprintf(buf + pos, remaining(pos), "%s:",
+ desc->function);
+ if (desc->flags & _DPRINTK_FLAGS_INCL_LINENO)
+ pos += snprintf(buf + pos, remaining(pos), "%d:", desc->lineno);
+ if (pos - pos_after_tid)
+ pos += snprintf(buf + pos, remaining(pos), " ");
+ if (pos >= PREFIX_SIZE)
+ buf[PREFIX_SIZE - 1] = '\0';
- if (descriptor->flags & _DPRINTK_FLAGS_INCL_LINENO)
- snprintf(lineno, sizeof(lineno), "%d", descriptor->lineno);
- else
- lineno[0] = 0;
-
- return printk(KERN_DEBUG "%s%s%s%s%s%s",
- tid,
- (descriptor->flags & _DPRINTK_FLAGS_INCL_MODNAME) ?
- descriptor->modname : "",
- (descriptor->flags & _DPRINTK_FLAGS_INCL_MODNAME) ?
- ":" : "",
- (descriptor->flags & _DPRINTK_FLAGS_INCL_FUNCNAME) ?
- descriptor->function : "",
- (descriptor->flags & _DPRINTK_FLAGS_INCL_FUNCNAME) ?
- ":" : "",
- lineno);
+ return buf;
}
int __dynamic_pr_debug(struct _ddebug *descriptor, const char *fmt, ...)
{
va_list args;
int res;
+ struct va_format vaf;
+ char buf[PREFIX_SIZE];
BUG_ON(!descriptor);
BUG_ON(!fmt);
va_start(args, fmt);
-
- res = dynamic_emit_prefix(descriptor);
- res += vprintk(fmt, args);
-
+ vaf.fmt = fmt;
+ vaf.va = &args;
+ res = printk("%s%pV", dynamic_emit_prefix(descriptor, buf), &vaf);
va_end(args);
return res;
@@ -480,18 +488,15 @@ int __dynamic_dev_dbg(struct _ddebug *descriptor,
struct va_format vaf;
va_list args;
int res;
+ char buf[PREFIX_SIZE];
BUG_ON(!descriptor);
BUG_ON(!fmt);
va_start(args, fmt);
-
vaf.fmt = fmt;
vaf.va = &args;
-
- res = dynamic_emit_prefix(descriptor);
- res += __dev_printk(KERN_CONT, dev, &vaf);
-
+ res = __dev_printk(dynamic_emit_prefix(descriptor, buf), dev, &vaf);
va_end(args);
return res;
@@ -504,18 +509,15 @@ int __dynamic_netdev_dbg(struct _ddebug *descriptor,
struct va_format vaf;
va_list args;
int res;
+ char buf[PREFIX_SIZE];
BUG_ON(!descriptor);
BUG_ON(!fmt);
va_start(args, fmt);
-
vaf.fmt = fmt;
vaf.va = &args;
-
- res = dynamic_emit_prefix(descriptor);
- res += __netdev_printk(KERN_CONT, dev, &vaf);
-
+ res = __netdev_printk(dynamic_emit_prefix(descriptor, buf), dev, &vaf);
va_end(args);
return res;