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perf: Fix perf_event_comm() vs. exec() assumption

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perf_event_comm() assumes that set_task_comm() is only called on
exec(), and in particular that its only called on current.

Neither are true, as Dave reported a WARN triggered by set_task_comm()
being called on !current.

Separate the exec() hook from the comm hook.

Reported-by: Dave Jones <davej@redhat.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/20140521153219.GH5226@laptop.programming.kicks-ass.net
[ Build fix. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2014-05-21 17:32:19 +02:00 committed by Ingo Molnar
parent 22c91aa235
commit e041e328c4
3 changed files with 20 additions and 13 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

1
fs/exec.c
View file

@ -1110,6 +1110,7 @@ void setup_new_exec(struct linux_binprm * bprm)
else
set_dumpable(current->mm, suid_dumpable);
perf_event_exec();
set_task_comm(current, kbasename(bprm->filename));
/* Set the new mm task size. We have to do that late because it may

4
include/linux/perf_event.h
View file

@ -695,6 +695,7 @@ extern struct perf_guest_info_callbacks *perf_guest_cbs;
extern int perf_register_guest_info_callbacks(struct perf_guest_info_callbacks *callbacks);
extern int perf_unregister_guest_info_callbacks(struct perf_guest_info_callbacks *callbacks);
extern void perf_event_exec(void);
extern void perf_event_comm(struct task_struct *tsk);
extern void perf_event_fork(struct task_struct *tsk);
@ -772,7 +773,7 @@ extern void perf_event_enable(struct perf_event *event);
extern void perf_event_disable(struct perf_event *event);
extern int __perf_event_disable(void *info);
extern void perf_event_task_tick(void);
#else
#else /* !CONFIG_PERF_EVENTS: */
static inline void
perf_event_task_sched_in(struct task_struct *prev,
struct task_struct *task) { }
@ -802,6 +803,7 @@ static inline int perf_unregister_guest_info_callbacks
(struct perf_guest_info_callbacks *callbacks) { return 0; }
static inline void perf_event_mmap(struct vm_area_struct *vma) { }
static inline void perf_event_exec(void) { }
static inline void perf_event_comm(struct task_struct *tsk) { }
static inline void perf_event_fork(struct task_struct *tsk) { }
static inline void perf_event_init(void) { }

28
kernel/events/core.c
View file

@ -2970,6 +2970,22 @@ static void perf_event_enable_on_exec(struct perf_event_context *ctx)
local_irq_restore(flags);
}
void perf_event_exec(void)
{
struct perf_event_context *ctx;
int ctxn;
rcu_read_lock();
for_each_task_context_nr(ctxn) {
ctx = current->perf_event_ctxp[ctxn];
if (!ctx)
continue;
perf_event_enable_on_exec(ctx);
}
rcu_read_unlock();
}
/*
* Cross CPU call to read the hardware event
*/
@ -5057,18 +5073,6 @@ static void perf_event_comm_event(struct perf_comm_event *comm_event)
void perf_event_comm(struct task_struct *task)
{
struct perf_comm_event comm_event;
struct perf_event_context *ctx;
int ctxn;
rcu_read_lock();
for_each_task_context_nr(ctxn) {
ctx = task->perf_event_ctxp[ctxn];
if (!ctx)
continue;
perf_event_enable_on_exec(ctx);
}
rcu_read_unlock();
if (!atomic_read(&nr_comm_events))
return;