[tip:sched/core] audit, sched/wait: Fixup kauditd_thread() wait loop

tip-bot for Peter Zijlstra
2014-11-04T16:09:47Z

Commit-ID: 6b55fc63f46ba299f3d84013e9232be4bd259eab
Gitweb: http://git.kernel.org/tip/6b55fc63f46ba299f3d84013e9232be4bd259eab
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Thu, 2 Oct 2014 12:22:51 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 4 Nov 2014 07:17:47 +0100

audit, sched/wait: Fixup kauditd_thread() wait loop

The kauditd_thread wait loop is a bit iffy; it has a number of problems:

- calls try_to_freeze() before schedule(); you typically want the
thread to re-evaluate the sleep condition when unfreezing, also
freeze_task() issues a wakeup.

- it unconditionally does the {add,remove}_wait_queue(), even when the
sleep condition is false.

Use wait_event_freezable() that does the right thing.

Reported-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Eric Paris <eparis@redhat.com>
Cc: oleg@redhat.com
Cc: Eric Paris <eparis@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20141002102251.GA6324@worktop.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
kernel/audit.c | 11 +----------
1 file changed, 1 insertion(+), 10 deletions(-)

diff --git a/kernel/audit.c b/kernel/audit.c
index 80983df..32bfc43 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -499,7 +499,6 @@ static int kauditd_thread(void *dummy)
set_freezable();
while (!kthread_should_stop()) {
struct sk_buff *skb;
- DECLARE_WAITQUEUE(wait, current);

flush_hold_queue();

@@ -514,16 +513,8 @@ static int kauditd_thread(void *dummy)
audit_printk_skb(skb);
continue;
}
- set_current_state(TASK_INTERRUPTIBLE);
- add_wait_queue(&kauditd_wait, &wait);

- if (!skb_queue_len(&audit_skb_queue)) {
- try_to_freeze();
- schedule();
- }
-
- __set_current_state(TASK_RUNNING);
- remove_wait_queue(&kauditd_wait, &wait);
+ wait_event_freezable(kauditd_wait, skb_queue_len(&audit_skb_queue));
}
return 0;
}