* [Suggestion] kernel: 'now' may be used uninitialized in posix_cpu_timer_schedule function
@ 2013-03-26 6:36 Chen Gang
2013-03-26 6:41 ` Chen Gang
2013-03-26 12:27 ` Frederic Weisbecker
0 siblings, 2 replies; 4+ messages in thread
From: Chen Gang @ 2013-03-26 6:36 UTC (permalink / raw)
To: tglx, Greg KH; +Cc: linux-kernel@vger.kernel.org
Hello Maintainers:
compiling with EXTRA_CFLAGS=-W:
make V=1 EXTRA_CFLAGS=-W ARCH=arm s3c2410_defconfig
make V=1 EXTRA_CFLAGS=-W ARCH=arm menuconfig
set 'arm-linux-gnu-' for cross chain prefix
make V=1 EXTRA_CFLAGS=-W ARCH=arm
it will report:
kernel/posix-cpu-timers.c:1065:19: warning: ‘now’ may be used uninitialized in this function [-Wuninitialized]
it seems it is really a bug.
can any member help to fix it ?
or provide additional suggestion ?
(it seems only "unsigned long long now = 0" is not enough).
:-)
in kernel/posix-cpu-timers.c:
for variable 'now' is defined without initialization (line 1029)
it may be used without initialization (line 1066)
1026 void posix_cpu_timer_schedule(struct k_itimer *timer)
1027 {
1028 struct task_struct *p = timer->it.cpu.task;
1029 unsigned long long now;
1030
1031 if (unlikely(p == NULL))
1032 /*
1033 * The task was cleaned up already, no future firings.
1034 */
1035 goto out;
1036
1037 /*
1038 * Fetch the current sample and update the timer's expiry time.
1039 */
1040 if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
1041 cpu_clock_sample(timer->it_clock, p, &now);
1042 bump_cpu_timer(timer, now);
1043 if (unlikely(p->exit_state)) {
1044 clear_dead_task(timer, now);
1045 goto out;
1046 }
1047 read_lock(&tasklist_lock); /* arm_timer needs it. */
1048 spin_lock(&p->sighand->siglock);
1049 } else {
1050 read_lock(&tasklist_lock);
1051 if (unlikely(p->sighand == NULL)) {
1052 /*
1053 * The process has been reaped.
1054 * We can't even collect a sample any more.
1055 */
1056 put_task_struct(p);
1057 timer->it.cpu.task = p = NULL;
1058 timer->it.cpu.expires = 0;
1059 goto out_unlock;
1060 } else if (unlikely(p->exit_state) && thread_group_empty(p)) {
1061 /*
1062 * We've noticed that the thread is dead, but
1063 * not yet reaped. Take this opportunity to
1064 * drop our task ref.
1065 */
1066 clear_dead_task(timer, now);
1067 goto out_unlock;
1068 }
1069 spin_lock(&p->sighand->siglock);
1070 cpu_timer_sample_group(timer->it_clock, p, &now);
1071 bump_cpu_timer(timer, now);
1072 /* Leave the tasklist_lock locked for the call below. */
1073 }
1074
1075 /*
1076 * Now re-arm for the new expiry time.
1077 */
1078 BUG_ON(!irqs_disabled());
1079 arm_timer(timer);
1080 spin_unlock(&p->sighand->siglock);
1081
1082 out_unlock:
1083 read_unlock(&tasklist_lock);
1084
1085 out:
1086 timer->it_overrun_last = timer->it_overrun;
1087 timer->it_overrun = -1;
1088 ++timer->it_requeue_pending;
1089 }
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [Suggestion] kernel: 'now' may be used uninitialized in posix_cpu_timer_schedule function
2013-03-26 6:36 [Suggestion] kernel: 'now' may be used uninitialized in posix_cpu_timer_schedule function Chen Gang
@ 2013-03-26 6:41 ` Chen Gang
2013-03-26 12:27 ` Frederic Weisbecker
1 sibling, 0 replies; 4+ messages in thread
From: Chen Gang @ 2013-03-26 6:41 UTC (permalink / raw)
To: tglx, Greg KH
Cc: linux-kernel@vger.kernel.org, linux-samsung-soc@vger.kernel.org,
Russell King - ARM Linux, linux-arm-kernel@lists.infradead.org,
kgene.kim@samsung.com
oh, sorry, it seems better to let ARM folks know about it.
;-)
On 2013年03月26日 14:36, Chen Gang wrote:
> Hello Maintainers:
>
> compiling with EXTRA_CFLAGS=-W:
> make V=1 EXTRA_CFLAGS=-W ARCH=arm s3c2410_defconfig
> make V=1 EXTRA_CFLAGS=-W ARCH=arm menuconfig
> set 'arm-linux-gnu-' for cross chain prefix
> make V=1 EXTRA_CFLAGS=-W ARCH=arm
>
> it will report:
> kernel/posix-cpu-timers.c:1065:19: warning: ‘now’ may be used uninitialized in this function [-Wuninitialized]
>
> it seems it is really a bug.
> can any member help to fix it ?
> or provide additional suggestion ?
> (it seems only "unsigned long long now = 0" is not enough).
>
> :-)
>
>
>
> in kernel/posix-cpu-timers.c:
> for variable 'now' is defined without initialization (line 1029)
> it may be used without initialization (line 1066)
>
>
> 1026 void posix_cpu_timer_schedule(struct k_itimer *timer)
> 1027 {
> 1028 struct task_struct *p = timer->it.cpu.task;
> 1029 unsigned long long now;
> 1030
> 1031 if (unlikely(p == NULL))
> 1032 /*
> 1033 * The task was cleaned up already, no future firings.
> 1034 */
> 1035 goto out;
> 1036
> 1037 /*
> 1038 * Fetch the current sample and update the timer's expiry time.
> 1039 */
> 1040 if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
> 1041 cpu_clock_sample(timer->it_clock, p, &now);
> 1042 bump_cpu_timer(timer, now);
> 1043 if (unlikely(p->exit_state)) {
> 1044 clear_dead_task(timer, now);
> 1045 goto out;
> 1046 }
> 1047 read_lock(&tasklist_lock); /* arm_timer needs it. */
> 1048 spin_lock(&p->sighand->siglock);
> 1049 } else {
> 1050 read_lock(&tasklist_lock);
> 1051 if (unlikely(p->sighand == NULL)) {
> 1052 /*
> 1053 * The process has been reaped.
> 1054 * We can't even collect a sample any more.
> 1055 */
> 1056 put_task_struct(p);
> 1057 timer->it.cpu.task = p = NULL;
> 1058 timer->it.cpu.expires = 0;
> 1059 goto out_unlock;
> 1060 } else if (unlikely(p->exit_state) && thread_group_empty(p)) {
> 1061 /*
> 1062 * We've noticed that the thread is dead, but
> 1063 * not yet reaped. Take this opportunity to
> 1064 * drop our task ref.
> 1065 */
> 1066 clear_dead_task(timer, now);
> 1067 goto out_unlock;
> 1068 }
> 1069 spin_lock(&p->sighand->siglock);
> 1070 cpu_timer_sample_group(timer->it_clock, p, &now);
> 1071 bump_cpu_timer(timer, now);
> 1072 /* Leave the tasklist_lock locked for the call below. */
> 1073 }
> 1074
> 1075 /*
> 1076 * Now re-arm for the new expiry time.
> 1077 */
> 1078 BUG_ON(!irqs_disabled());
> 1079 arm_timer(timer);
> 1080 spin_unlock(&p->sighand->siglock);
> 1081
> 1082 out_unlock:
> 1083 read_unlock(&tasklist_lock);
> 1084
> 1085 out:
> 1086 timer->it_overrun_last = timer->it_overrun;
> 1087 timer->it_overrun = -1;
> 1088 ++timer->it_requeue_pending;
> 1089 }
>
--
Chen Gang
Asianux Corporation
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [Suggestion] kernel: 'now' may be used uninitialized in posix_cpu_timer_schedule function
2013-03-26 6:36 [Suggestion] kernel: 'now' may be used uninitialized in posix_cpu_timer_schedule function Chen Gang
2013-03-26 6:41 ` Chen Gang
@ 2013-03-26 12:27 ` Frederic Weisbecker
2013-03-26 12:32 ` Chen Gang
1 sibling, 1 reply; 4+ messages in thread
From: Frederic Weisbecker @ 2013-03-26 12:27 UTC (permalink / raw)
To: Chen Gang; +Cc: tglx, Greg KH, linux-kernel@vger.kernel.org, Andrew Morton
2013/3/26 Chen Gang <gang.chen@asianux.com>:
> Hello Maintainers:
>
> compiling with EXTRA_CFLAGS=-W:
> make V=1 EXTRA_CFLAGS=-W ARCH=arm s3c2410_defconfig
> make V=1 EXTRA_CFLAGS=-W ARCH=arm menuconfig
> set 'arm-linux-gnu-' for cross chain prefix
> make V=1 EXTRA_CFLAGS=-W ARCH=arm
>
> it will report:
> kernel/posix-cpu-timers.c:1065:19: warning: ‘now’ may be used uninitialized in this function [-Wuninitialized]
>
> it seems it is really a bug.
> can any member help to fix it ?
> or provide additional suggestion ?
> (it seems only "unsigned long long now = 0" is not enough).
Yeah it's missing a call to cpu_timer_sample_group() before
clear_dead_task(). Andrew Morton reported the warning and I have a
pending patch to fix that. I'm just checking a few other things before
sending it. These clear_dead_task() calls seem to also conflict with
cleanup_timers(). I'm fixing that too.
Thanks for your report!
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [Suggestion] kernel: 'now' may be used uninitialized in posix_cpu_timer_schedule function
2013-03-26 12:27 ` Frederic Weisbecker
@ 2013-03-26 12:32 ` Chen Gang
0 siblings, 0 replies; 4+ messages in thread
From: Chen Gang @ 2013-03-26 12:32 UTC (permalink / raw)
To: Frederic Weisbecker
Cc: tglx, Greg KH, linux-kernel@vger.kernel.org, Andrew Morton
On 2013年03月26日 20:27, Frederic Weisbecker wrote:
> 2013/3/26 Chen Gang <gang.chen@asianux.com>:
>> > Hello Maintainers:
>> >
>> > compiling with EXTRA_CFLAGS=-W:
>> > make V=1 EXTRA_CFLAGS=-W ARCH=arm s3c2410_defconfig
>> > make V=1 EXTRA_CFLAGS=-W ARCH=arm menuconfig
>> > set 'arm-linux-gnu-' for cross chain prefix
>> > make V=1 EXTRA_CFLAGS=-W ARCH=arm
>> >
>> > it will report:
>> > kernel/posix-cpu-timers.c:1065:19: warning: �now� may be used uninitialized in this function [-Wuninitialized]
>> >
>> > it seems it is really a bug.
>> > can any member help to fix it ?
>> > or provide additional suggestion ?
>> > (it seems only "unsigned long long now = 0" is not enough).
> Yeah it's missing a call to cpu_timer_sample_group() before
> clear_dead_task(). Andrew Morton reported the warning and I have a
> pending patch to fix that. I'm just checking a few other things before
> sending it. These clear_dead_task() calls seem to also conflict with
> cleanup_timers(). I'm fixing that too.
>
> Thanks for your report!
>
>
thank you, too.
:-)
--
Chen Gang
Asianux Corporation
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2013-03-26 12:32 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2013-03-26 6:36 [Suggestion] kernel: 'now' may be used uninitialized in posix_cpu_timer_schedule function Chen Gang
2013-03-26 6:41 ` Chen Gang
2013-03-26 12:27 ` Frederic Weisbecker
2013-03-26 12:32 ` Chen Gang
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox