From: Steven Rostedt Date: Tue, 3 Dec 2013 17:41:20 +0000 (-0500) Subject: tracing: Only run synchronize_sched() at instance deletion time X-Git-Tag: v3.13-rc3~1^2 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3ccb01239201af06a07482ec686b14cd148102a5;p=pandora-kernel.git tracing: Only run synchronize_sched() at instance deletion time It has been reported that boot up with FTRACE_SELFTEST enabled can take a very long time. There can be stalls of over a minute. This was tracked down to the synchronize_sched() called when a system call event is disabled. As the self tests enable and disable thousands of events, this makes the synchronize_sched() get called thousands of times. The synchornize_sched() was added with d562aff93bfb53 "tracing: Add support for SOFT_DISABLE to syscall events" which caused this regression (added in 3.13-rc1). The synchronize_sched() is to protect against the events being accessed when a tracer instance is being deleted. When an instance is being deleted all the events associated to it are unregistered. The synchronize_sched() makes sure that no more users are running when it finishes. Instead of calling synchronize_sched() for all syscall events, we only need to call it once, after the events are unregistered and before the instance is deleted. The event_mutex is held during this action to prevent new users from enabling events. Link: http://lkml.kernel.org/r/20131203124120.427b9661@gandalf.local.home Reported-by: Petr Mladek Acked-by: Tom Zanussi Acked-by: Petr Mladek Tested-by: Petr Mladek Signed-off-by: Steven Rostedt --- Reading git-diff-tree failed