[JAUNTY] SRU: UBUNTU: posix timers: fix RLIMIT_CPU && fork()

[Stefan Bader]

ACK

Manoj Iyer wrote:
> SRU JUSTIFICATION:
> 
> IMPACT: ulimit -t doesn't work in Ubuntu 09.04
> FIX: This is a workaround patch for 2.6.28.
> TEST: Originator of the bug tested the kernel in 
> http://people.ubuntu.com/~manjo/lp361508-jaunty/ and reported to work.
> 
> 
> The following changes since commit 
> a63b7d7beeaa1f8f33369cab6419831fa8991e40:
>    Tyler Hicks (1):
>          UBUNTU: SAUCE: (drop after 2.6.28) [PATCH] eCryptfs: Larger buffer 
> for encrypted symlink targets
> 
> are available in the git repository at:
> 
>    git://kernel.ubuntu.com/manjo/ubuntu-jaunty.git lp361508
> 
> Oleg Nesterov (1):
>        UBUNTU: posix timers: fix RLIMIT_CPU && fork()
> 
>   kernel/posix-cpu-timers.c |    3 ++-
>   1 files changed, 2 insertions(+), 1 deletions(-)
> 
> From bb56a0cce2d85ada3a2075fb245c2657cc9711de Mon Sep 17 00:00:00 2001
> From: Oleg Nesterov <oleg at redhat.com>
> Date: Mon, 23 Mar 2009 20:34:11 +0100
> Subject: [PATCH] UBUNTU: posix timers: fix RLIMIT_CPU && fork()
> 
> BUG: #361508
> BugLink: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/361508
> 
> 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 cpu timers.
> 
> This is the minimal fix for 2.6.29 (tested) and 2.6.28. The patch is not
> optimal, we need further cleanups here. With this patch update_rlimit_cpu()
> is not really needed, but I don't think it should be removed.
> 
> The proper fix (I think) is:
> 
>  	- set_process_cpu_timer() should just start the cputimer->running
>  	  logic (it does), no need to change cputime_expires.xxx_exp
> 
>  	- posix_cpu_timers_init_group() should set ->running when needed
> 
>  	- fastpath_timer_check() can check ->running instead of
>  	  task_cputime_zero(signal->cputime_expires)
> 
> Reported-by: Peter Lojkin <ia6432 at inbox.ru>
> Signed-off-by: Oleg Nesterov <oleg at redhat.com>
> Cc: Peter Zijlstra <peterz at infradead.org>
> Cc: Roland McGrath <roland at redhat.com>
> Cc: <stable at kernel.org> [for 2.6.29.x]
> LKML-Reference: <20090323193411.GA17514 at redhat.com>
> Signed-off-by: Ingo Molnar <mingo at elte.hu>
> Signed-off-by: Manoj Iyer <manoj.iyer at canonical.com>
> 
> Author:    Oleg Nesterov <oleg at redhat.com>
> ---
>   kernel/posix-cpu-timers.c |    3 ++-
>   1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
> index 4e5288a..c165985 100644
> --- a/kernel/posix-cpu-timers.c
> +++ b/kernel/posix-cpu-timers.c
> @@ -1333,7 +1333,8 @@ static inline int fastpath_timer_check(struct task_struct *tsk)
>   		if (task_cputime_expired(&group_sample, &sig->cputime_expires))
>   			return 1;
>   	}
> -	return 0;
> +
> +	return sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY;
>   }
> 
>   /*


-- 

When all other means of communication fail, try words!