jump_label: Fix concurrent static_key_enable/disable()
authorPaolo Bonzini <pbonzini@redhat.com>
Tue, 1 Aug 2017 15:24:04 +0000 (17:24 +0200)
committerIngo Molnar <mingo@kernel.org>
Thu, 10 Aug 2017 10:28:56 +0000 (12:28 +0200)
commit1dbb6704de91b169a58d0c8221624afd6a95cfc7
tree46273515a9b79413d2f00629b7e253189e903219
parent83ced169d9a01f22eb39f1fcc1f89ad9d223238f
jump_label: Fix concurrent static_key_enable/disable()

static_key_enable/disable are trying to cap the static key count to
0/1.  However, their use of key->enabled is outside jump_label_lock
so they do not really ensure that.

Rewrite them to do a quick check for an already enabled (respectively,
already disabled), and then recheck under the jump label lock.  Unlike
static_key_slow_inc/dec, a failed check under the jump label lock does
not modify key->enabled.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Jason Baron <jbaron@akamai.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1501601046-35683-2-git-send-email-pbonzini@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
include/linux/jump_label.h
kernel/jump_label.c