posix-timers: fix RLIMIT_CPU && fork()

See http://bugzilla.kernel.org/show_bug.cgi?id=12911

copy_signal() copies signal->rlim, but RLIMIT_CPU is "lost". Because
posix_cpu_timers_init_group() sets cputime_expires.prof_exp = 0 and thus
fastpath_timer_check() returns false unless we have other expired cpu timers.

Change copy_signal() to set cputime_expires.prof_exp if we have RLIMIT_CPU.
Also, set cputimer.running = 1 in that case. This is not strictly necessary,
but imho makes sense.

Reported-by: Peter Lojkin <ia6432@inbox.ru>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Peter Lojkin <ia6432@inbox.ru>
Cc: Roland McGrath <roland@redhat.com>
Cc: stable@kernel.org
LKML-Reference: <20090327000607.GA10104@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/fork.c b/kernel/fork.c
index 4854c2c..9b51a1b 100644 (file)
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -808,6 +808,12 @@ static void posix_cpu_timers_init_group(struct signal_struct *sig)
        sig->cputime_expires.virt_exp = cputime_zero;
        sig->cputime_expires.sched_exp = 0;
 
+       if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
+               sig->cputime_expires.prof_exp =
+                       secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
+               sig->cputimer.running = 1;
+       }
+
        /* The timer lists. */
        INIT_LIST_HEAD(&sig->cpu_timers[0]);
        INIT_LIST_HEAD(&sig->cpu_timers[1]);
@@ -823,11 +829,8 @@ static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
                atomic_inc(&current->signal->live);
                return 0;
        }
-       sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
-
-       if (sig)
-               posix_cpu_timers_init_group(sig);
 
+       sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
        tsk->signal = sig;
        if (!sig)
                return -ENOMEM;
@@ -865,6 +868,8 @@ static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
        memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
        task_unlock(current->group_leader);
 
+       posix_cpu_timers_init_group(sig);
+
        acct_init_pacct(&sig->pacct);
 
        tty_audit_fork(sig);