| Message ID | 20120324103127.GJ29067@lizard (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
On Sat, 2012-03-24 at 14:31 +0400, Anton Vorontsov wrote: > This is needed so that callers would not get 'context imbalance' > warnings from the sparse tool. > > As a side effect, this patch fixes the following sparse warnings: > > CHECK mm/oom_kill.c > mm/oom_kill.c:201:28: warning: context imbalance in 'oom_badness' - > unexpected unlock > include/linux/rcupdate.h:249:30: warning: context imbalance in > 'dump_tasks' - unexpected unlock > mm/oom_kill.c:453:9: warning: context imbalance in 'oom_kill_task' - > unexpected unlock > CHECK mm/memcontrol.c > ... > mm/memcontrol.c:1130:17: warning: context imbalance in > 'task_in_mem_cgroup' - unexpected unlock > > p.s. I know Peter Zijlstra detest the __cond_lock() stuff, but untill > we have anything better in sparse, let's use it. This particular > patch helped me to detect one bug that I myself made during > task->mm fixup series. So, it is useful. Yeah, so Nacked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Also, why didn't lockdep catch it? Fix sparse already instead of smearing ugly all over.
On Sat, Mar 24, 2012 at 01:52:54PM +0100, Peter Zijlstra wrote: [...] > > p.s. I know Peter Zijlstra detest the __cond_lock() stuff, but untill > > we have anything better in sparse, let's use it. This particular > > patch helped me to detect one bug that I myself made during > > task->mm fixup series. So, it is useful. > > Yeah, so Nacked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> > > Also, why didn't lockdep catch it? Because patch authors test their patches on architectures they own (well, sometimes I do check patches on exotic architectures w/ qemu, but it is less convenient than just build/sparse-test the patch w/ a cross compiler). And since lockdep is a runtime checker, it is not very useful. Sparse is a build-time checker, so it is even better in the sense that it is able to catch bugs even in code that is executed rarely. > Fix sparse already instead of smearing ugly all over. Just wonder how do you see the feature implemented? Something like this? #define __ret_cond_locked(l, c) __attribute__((ret_cond_locked(l, c))) #define __ret_value __attribute__((ret_value)) #define __ret_locked_nonnull(l) __ret_cond_locked(l, __ret_value); extern struct task_struct *find_lock_task_mm(struct task_struct *p) __ret_locked_nonnull(&__ret_value->alloc_lock); Thanks,
On Sat, 2012-03-24 at 20:21 +0400, Anton Vorontsov wrote: > Just wonder how do you see the feature implemented? > > Something like this? > > #define __ret_cond_locked(l, c) __attribute__((ret_cond_locked(l, c))) > #define __ret_value __attribute__((ret_value)) > #define __ret_locked_nonnull(l) __ret_cond_locked(l, __ret_value); > > extern struct task_struct *find_lock_task_mm(struct task_struct *p) > __ret_locked_nonnull(&__ret_value->alloc_lock); Yeah, see the email I just CC'ed you on to linux-sparse. Basically extend __attribute__((context())) to allow things similar to what you proposed.
On Sat, 24 Mar 2012, Peter Zijlstra wrote: > Yeah, so Nacked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> > > Also, why didn't lockdep catch it? > > Fix sparse already instead of smearing ugly all over. > Fully agreed, please don't add this to the oom killer.
diff --git a/include/linux/oom.h b/include/linux/oom.h index 552fba9..26cf628 100644 --- a/include/linux/oom.h +++ b/include/linux/oom.h @@ -21,6 +21,7 @@ #ifdef __KERNEL__ +#include <linux/compiler.h> #include <linux/sched.h> #include <linux/types.h> #include <linux/nodemask.h> @@ -65,7 +66,16 @@ static inline void oom_killer_enable(void) oom_killer_disabled = false; } -extern struct task_struct *find_lock_task_mm(struct task_struct *p); +extern struct task_struct *__find_lock_task_mm(struct task_struct *p); + +static inline struct task_struct *find_lock_task_mm(struct task_struct *p) +{ + struct task_struct *ret; + + ret = __find_lock_task_mm(p); + (void)__cond_lock(&ret->alloc_lock, ret); + return ret; +} /* sysctls */ extern int sysctl_oom_dump_tasks; diff --git a/mm/oom_kill.c b/mm/oom_kill.c index 2958fd8..0ebb383 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -136,7 +136,7 @@ static bool has_intersects_mems_allowed(struct task_struct *tsk, * pointer. Return p, or any of its subthreads with a valid ->mm, with * task_lock() held. */ -struct task_struct *find_lock_task_mm(struct task_struct *p) +struct task_struct *__find_lock_task_mm(struct task_struct *p) { struct task_struct *t = p;
This is needed so that callers would not get 'context imbalance' warnings from the sparse tool. As a side effect, this patch fixes the following sparse warnings: CHECK mm/oom_kill.c mm/oom_kill.c:201:28: warning: context imbalance in 'oom_badness' - unexpected unlock include/linux/rcupdate.h:249:30: warning: context imbalance in 'dump_tasks' - unexpected unlock mm/oom_kill.c:453:9: warning: context imbalance in 'oom_kill_task' - unexpected unlock CHECK mm/memcontrol.c ... mm/memcontrol.c:1130:17: warning: context imbalance in 'task_in_mem_cgroup' - unexpected unlock p.s. I know Peter Zijlstra detest the __cond_lock() stuff, but untill we have anything better in sparse, let's use it. This particular patch helped me to detect one bug that I myself made during task->mm fixup series. So, it is useful. Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org> Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> --- include/linux/oom.h | 12 +++++++++++- mm/oom_kill.c | 2 +- 2 files changed, 12 insertions(+), 2 deletions(-)