Commit e041e328 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

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



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: default avatarDave Jones <davej@redhat.com>
Signed-off-by: default avatarPeter 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: default avatarIngo Molnar <mingo@kernel.org>
parent 22c91aa2

fs/exec.c

+1 −0
Original line number Diff line number Diff line
@@ -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

include/linux/perf_event.h

+3 −1
Original line number Diff line number Diff line
@@ -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)				{ }

kernel/events/core.c

+16 −12
Original line number Diff line number Diff line
@@ -2970,6 +2970,22 @@ out: 
	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;

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