posix-timers: Use sighand lock instead of tasklist_lock for task clock sample
There is no need for the tasklist_lock just to take a process
wide clock sample.
All we need is to get a coherent sample that doesn't race with
exit() and exec():
* exit() may be concurrently reaping a task and flushing its time
* sighand is unstable under exit() and exec(), and the latter also
result in group leader that can change
To protect against these, locking the target's sighand is enough.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Kosaki Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
1 file changed