linux-kernel - [tip:timers/urgent] posix-timers: fix RLIMIT_CPU && setitimer(CPUCLOCK

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Date:	Wed, 8 Apr 2009 16:09:49 GMT
From:	Oleg Nesterov <oleg@...hat.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	ia6432@...ox.ru, peterz@...radead.org, roland@...hat.com,
	tglx@...utronix.de, oleg@...hat.com, mingo@...e.hu
Subject: [tip:timers/urgent] posix-timers: fix RLIMIT_CPU && setitimer(CPUCLOCK_PROF)

Commit-ID:  8f2e586567b1bad72dac7c3810fe9a2ef7117506
Gitweb:     http://git.kernel.org/tip/8f2e586567b1bad72dac7c3810fe9a2ef7117506
Author:     Oleg Nesterov <oleg@...hat.com>
AuthorDate: Fri, 27 Mar 2009 01:06:10 +0100
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Wed, 8 Apr 2009 17:51:39 +0200

posix-timers: fix RLIMIT_CPU && setitimer(CPUCLOCK_PROF)

update_rlimit_cpu() tries to optimize out set_process_cpu_timer() in case
when we already have CPUCLOCK_PROF timer which should expire first. But it
uses cputime_lt() instead of cputime_gt().

Test case:

	int main(void)
	{
		struct itimerval it = {
			.it_value = { .tv_sec = 1000 },
		};

		assert(!setitimer(ITIMER_PROF, &it, NULL));

		struct rlimit rl = {
			.rlim_cur = 1,
			.rlim_max = 1,
		};

		assert(!setrlimit(RLIMIT_CPU, &rl));

		for (;;)
			;

		return 0;
	}

Without this patch, the task is not killed as RLIMIT_CPU demands.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
Acked-by: Peter Zijlstra <peterz@...radead.org>
Cc: Peter Lojkin <ia6432@...ox.ru>
Cc: Roland McGrath <roland@...hat.com>
Cc: stable@...nel.org
LKML-Reference: <20090327000610.GA10108@...hat.com>
Signed-off-by: Ingo Molnar <mingo@...e.hu>


---
 kernel/posix-cpu-timers.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index 8e5d9a6..bb53185 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -18,7 +18,7 @@ void update_rlimit_cpu(unsigned long rlim_new)
 
 	cputime = secs_to_cputime(rlim_new);
 	if (cputime_eq(current->signal->it_prof_expires, cputime_zero) ||
-	    cputime_lt(current->signal->it_prof_expires, cputime)) {
+	    cputime_gt(current->signal->it_prof_expires, cputime)) {
 		spin_lock_irq(&current->sighand->siglock);
 		set_process_cpu_timer(current, CPUCLOCK_PROF, &cputime, NULL);
 		spin_unlock_irq(&current->sighand->siglock);
--
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