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authorJiri Kosina <jkosina@suse.cz>2007-07-15 23:41:51 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-07-16 09:05:52 -0700
commit1492192b4a0bb84dd9b792cc0bd30583220a28a7 (patch)
tree54763778f2c1ed69ae967022dd940b4bcc040120
parent017f021c7e5fe3f82ccc5cbb7b1750e66e00f527 (diff)
kernel/printk.c: document possible deadlock against scheduler
kernel/printk.c: document possible deadlock against scheduler The printk's comment states that it can be called from every context, which might lead to false illusion that it could be called from everywhere without any restrictions. This is however not true - a call to printk() could deadlock if called from scheduler code (namely from schedule(), wake_up(), etc) on runqueue lock when it tries to wake up klogd. Document this. Signed-off-by: Jiri Kosina <jkosina@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--kernel/printk.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/kernel/printk.c b/kernel/printk.c
index fccacf706f5..051d27e36a6 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -486,6 +486,9 @@ static int have_callable_console(void)
* @fmt: format string
*
* This is printk(). It can be called from any context. We want it to work.
+ * Be aware of the fact that if oops_in_progress is not set, we might try to
+ * wake klogd up which could deadlock on runqueue lock if printk() is called
+ * from scheduler code.
*
* We try to grab the console_sem. If we succeed, it's easy - we log the output and
* call the console drivers. If we fail to get the semaphore we place the output