linux-kernel - Re: [PATCH] tracing: Add task activate/deactivate tracepoints

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1275322715.27810.23323.camel@twins>
Date:	Mon, 31 May 2010 18:18:35 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH] tracing: Add task activate/deactivate tracepoints

On Mon, 2010-05-31 at 16:48 +0200, Frederic Weisbecker wrote:
> > Should we maybe cure this and rely on sched_switch() to detect sleeps?
> > It seems natural since only the current task can go to sleep, its just
> > that the whole preempt state gets a bit iffy.

How about something like the below?

Steve, is that proper usage of CREATE_TRACE_POINT?

---
Subject: sched, trace: Fix sched_switch() prev_state argument
From: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Date: Mon May 31 18:13:25 CEST 2010

For CONFIG_PREEMPT=y kernels the sched_switch(.prev_state) argument
isn't useful because we can get preempted with current->state !=
TASK_RUNNING without actually getting removed from the runqueue.

Cure this by treating all preempted tasks as runnable from the
tracer's point of view.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
---
 include/trace/events/sched.h |   19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

Index: linux-2.6/include/trace/events/sched.h
===================================================================
--- linux-2.6.orig/include/trace/events/sched.h
+++ linux-2.6/include/trace/events/sched.h
@@ -115,6 +115,23 @@ DEFINE_EVENT(sched_wakeup_template, sche
 	     TP_PROTO(struct task_struct *p, int success),
 	     TP_ARGS(p, success));
 
+#ifdef CREATE_TRACE_POINTS
+static inline long __trace_sched_switch_state(struct task_struct *p)
+{
+	long state = p->state;
+
+#ifdef CONFIG_PREEMPT
+	/*
+	 * For all intents and purposes a preempted task is a running task.
+	 */
+	if (task_thread_info(p)->preempt_count & PREEMPT_ACTIVE)
+		state = TASK_RUNNING;
+#endif
+
+	return state;
+}
+#endif
+
 /*
  * Tracepoint for task switches, performed by the scheduler:
  */
@@ -139,7 +156,7 @@ TRACE_EVENT(sched_switch,
 		memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN);
 		__entry->prev_pid	= prev->pid;
 		__entry->prev_prio	= prev->prio;
-		__entry->prev_state	= prev->state;
+		__entry->prev_state	= __trace_sched_switch_state(prev);
 		memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN);
 		__entry->next_pid	= next->pid;
 		__entry->next_prio	= next->prio;

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/