linux-kernel - Re: [PATCH] show message when exceeded rlimit of pending signals

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Date:	Tue, 27 Oct 2009 01:39:14 +0900
From:	Naohiro Ooiwa <nooiwa@...aclelinux.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	roland@...hat.com, akpm@...ux-foundation.org, oleg@...hat.com,
	LKML <linux-kernel@...r.kernel.org>, h-shimamoto@...jp.nec.com,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH] show message when exceeded rlimit of pending signals

Hi Ingo,

Now that you mention it, I think so, too.
I update my patch.

How is the following patch.
Could you please review it.

Thanks you.
Naohiro Ooiwa



Signed-off-by: Naohiro Ooiwa <nooiwa@...aclelinux.com>
---
 Documentation/kernel-parameters.txt |    9 ++++++++-
 kernel/signal.c                     |   16 +++++++++++++---
 2 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/Documentation/kernel-parameters.txt
b/Documentation/kernel-parameters.txt
index 9107b38..01c2723 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2032,8 +2032,15 @@ and is between 256 and 4096 characters. It is
defined in the file

 	print-fatal-signals=
 			[KNL] debug: print fatal signals
+			If you would like to know what the cause of a coredump
+			by signal number, if your working system may have
+			too many POSIX.1 timers, and when during the system
+			test,you may as well to enable this parameter.
 			print-fatal-signals=1: print segfault info to
-			the kernel console.
+			the kernel console, and print caution that reached the
+			limit of pending signals to the kernel console.
+			When printed the caution messages, you can try
+			"ulimit -i unlimited".
 			default: off.

 	printk.time=	Show timing data prefixed to each printk message line
diff --git a/kernel/signal.c b/kernel/signal.c
index 6705320..137112e 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -188,6 +188,14 @@ int next_signal(struct sigpending *pending,
sigset_t *mask)
 	return sig;
 }

+int print_fatal_signals;
+
+static void show_reach_rlimit_sigpending(void)
+{
+	if (printk_ratelimit())
+		printk(KERN_WARNING "%s/%d: reached the limit of pending signals.\n",
current->comm, current->pid);
+}
+
 /*
  * allocate a new signal queue record
  * - this may be called without locks if and only if t == current,
otherwise an
@@ -209,8 +217,12 @@ static struct sigqueue *__sigqueue_alloc(struct
task_struct *t, gfp_t flags,
 	atomic_inc(&user->sigpending);
 	if (override_rlimit ||
 	    atomic_read(&user->sigpending) <=
-			t->signal->rlim[RLIMIT_SIGPENDING].rlim_cur)
+			t->signal->rlim[RLIMIT_SIGPENDING].rlim_cur) {
 		q = kmem_cache_alloc(sigqueue_cachep, flags);
+	} else {
+		if (print_fatal_signals)
+			show_reach_rlimit_sigpending();
+	}
 	if (unlikely(q == NULL)) {
 		atomic_dec(&user->sigpending);
 		free_uid(user);
@@ -925,8 +937,6 @@ static int send_signal(int sig, struct siginfo
*info, struct task_struct *t,
 	return __send_signal(sig, info, t, group, from_ancestor_ns);
 }

-int print_fatal_signals;
-
 static void print_fatal_signal(struct pt_regs *regs, int signr)
 {
 	printk("%s/%d: potentially unexpected fatal signal %d.\n",
-- 1.5.4.1


Ingo Molnar wrote:
> * nooiwa <nooiwa@...aclelinux.com> wrote:
> 
>> +++ b/kernel/sysctl.c
>> @@ -67,6 +67,7 @@ static int deprecated_sysctl_warning(struct __sysctl_args *args);
>>  /* External variables not in a header file. */
>>  extern int C_A_D;
>>  extern int print_fatal_signals;
>> +extern int print_reach_rlimit_sigpending;
> 
> Ooiwa-san, Roland, Andrew - what do you think about just making this 
> part of the existing print_fatal_signals flag, instead of adding a new 
> one?
> 
> Signal queue overflows are a 'fatal', signal-related condition as well - 
> we lose a signal in essence. The patch would be smaller as well.
> 
> 	Ingo

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