From 5be71b61f17b0e3bc8ad0b1a1b7b53ab7d574ebb Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Sun, 15 Mar 2009 22:10:37 +0100 Subject: [PATCH] tracing/syscalls: protect thread flag toggling from races Impact: fix syscall tracer enable/disable race The current thread flag toggling is racy as shown in the following scenario: - task A is the last user of syscall tracing, it releases the TIF_SYSCALL_FTRACE on each tasks - at the same time task B start syscall tracing. refcount == 0 so it sets up TIF_SYSCALL_FTRACE on each tasks. The effect of the mixup is unpredictable. So this fix adds a mutex on {start,stop}_syscall_tracing(). Reported-by: Andrew Morton Reported-by: Ingo Molnar LKML-Reference: <1237151439-6755-3-git-send-email-fweisbec@gmail.com> Signed-off-by: Ingo Molnar --- Reading git-format-patch failed