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SubjectRe: [PATCH] show message when exceeded rlimit of pending signals
Hi Ingo,

> Here's a slightly improved version of the text:

Thank you for your review and collect my English.

>> +int print_fatal_signals;
>
> i'd suggest __read_mostly.

> Plus please move variables to the top of the file. (i know this comes
> from the previous code but we can improve it while we are touching it)

Of course. You're right, if we found one like it,
I want to improve the code little by little too.

How is the following patch.

Signed-off-by: Naohiro Ooiwa <nooiwa@miraclelinux.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
---
Documentation/kernel-parameters.txt | 13 ++++++++++---
kernel/signal.c | 16 +++++++++++++---
2 files changed, 23 insertions(+), 6 deletions(-)
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 9107b38..8492ad3 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2032,9 +2032,16 @@ and is between 256 and 4096 characters. It is defined in the file

print-fatal-signals=
[KNL] debug: print fatal signals
- print-fatal-signals=1: print segfault info to
- the kernel console.
- default: off.
+
+ If enabled, warn about various signal handling
+ related application anomalies: too many signals,
+ too many POSIX.1 timers, fatal signals causing a
+ coredump - etc.
+
+ If you hit the warning due to signal overflow,
+ you might want to try "ulimit -i unlimited".
+
+ default: off.

printk.time= Show timing data prefixed to each printk message line
Format: <bool> (1/Y/y=enable, 0/N/n=disable)
diff --git a/kernel/signal.c b/kernel/signal.c
index 6705320..c913eb7 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -41,6 +41,8 @@

static struct kmem_cache *sigqueue_cachep;

+int print_fatal_signals __read_mostly;
+
static void __user *sig_handler(struct task_struct *t, int sig)
{
return t->sighand->action[sig - 1].sa.sa_handler;
@@ -188,6 +190,12 @@ int next_signal(struct sigpending *pending, sigset_t *mask)
return sig;
}

+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:
> * Naohiro Ooiwa <nooiwa@miraclelinux.com> wrote:
>
>> 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@miraclelinux.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.
>>
>
> Here's a slightly improved version of the text:
>
> print-fatal-signals=
> [KNL] debug: print fatal signals
>
> If enabled, warn about various signal handling
> related application anomalies: too many signals,
> too many POSIX.1 timers, fatal signals causing a
> coredump - etc.
>
> If you hit the warning due to signal overflow,
> you might want to try "ulimit -i unlimited".
>
> default: off.
>
>> +int print_fatal_signals;
>
> i'd suggest __read_mostly.
>
> Plus please move variables to the top of the file. (i know this comes
> from the previous code but we can improve it while we are touching it)
>
> With these things addressed it looks good to me:
>
> Acked-by: Ingo Molnar <mingo@elte.hu>
>
> Ingo
>



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