linux-kernel - Re: [PATCH 0/6] ftrace: port to the new ring

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Date:	Tue, 30 Sep 2008 11:13:05 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Mathieu Desnoyers <compudj@...stal.dyndns.org>
Subject: Re: [PATCH 0/6] ftrace: port to the new ring_buffer


ok, -tip testing found a serious-looking locking bug:

[    4.044005] calling  init_irqsoff_tracer+0x0/0x11 @ 1
[    4.048005] Testing tracer irqsoff: 
[    4.056202] =============================================
[    4.060000] [ INFO: possible recursive locking detected ]
[    4.060000] 2.6.27-rc8-tip-00917-g01214de-dirty #37512
[    4.060000] ---------------------------------------------
[    4.060000] swapper/1 is trying to acquire lock:
[    4.060000]  (&cpu_buffer->lock){++..}, at: [<c015a216>] ring_buffer_lock+0x3b/0x50
[    4.060000] 
[    4.060000] but task is already holding lock:
[    4.060000]  (&cpu_buffer->lock){++..}, at: [<c015a216>] ring_buffer_lock+0x3b/0x50
[    4.060000] 
[    4.060000] other info that might help us debug this:
[    4.060000] 3 locks held by swapper/1:
[    4.060000]  #0:  (trace_types_lock){--..}, at: [<c015d758>] register_tracer+0x2f/0x14f
[    4.060000]  #1:  (max_trace_lock){....}, at: [<c015eab0>] check_critical_timing+0x5d/0x113
[    4.060000]  #2:  (&cpu_buffer->lock){++..}, at: [<c015a216>] ring_buffer_lock+0x3b/0x50
[    4.060000] 
[    4.060000] stack backtrace:
[    4.060000] Pid: 1, comm: swapper Not tainted 2.6.27-rc8-tip-00917-g01214de-dirty #37512
[    4.060000]  [<c014446d>] validate_chain+0x4e9/0xb4c
[    4.060000]  [<c0108b54>] ? native_sched_clock+0xe2/0x101
[    4.060000]  [<c014519a>] __lock_acquire+0x6ca/0x730
[    4.060000]  [<c014525b>] lock_acquire+0x5b/0x81
[    4.060000]  [<c015a216>] ? ring_buffer_lock+0x3b/0x50
[    4.060000]  [<c05908cf>] _spin_lock+0x23/0x50
[    4.060000]  [<c015a216>] ? ring_buffer_lock+0x3b/0x50
[    4.060000]  [<c015a216>] ring_buffer_lock+0x3b/0x50
[    4.060000]  [<c015a2b3>] ring_buffer_reset+0x16/0x46
[    4.060000]  [<c015e16f>] update_max_tr_single+0x65/0xc0
[    4.060000]  [<c015eb15>] check_critical_timing+0xc2/0x113
[    4.060000]  [<c015d270>] ? trace_selftest_startup_irqsoff+0x49/0xac
[    4.060000]  [<c015d270>] ? trace_selftest_startup_irqsoff+0x49/0xac
[    4.060000]  [<c015ec0c>] time_hardirqs_on+0xa6/0xb9
[    4.060000]  [<c014393c>] ? trace_hardirqs_on+0xb/0xd
[    4.060000]  [<c01437fb>] trace_hardirqs_on_caller+0x16/0x14c
[    4.060000]  [<c014393c>] trace_hardirqs_on+0xb/0xd
[    4.060000]  [<c015d270>] trace_selftest_startup_irqsoff+0x49/0xac
[    4.060000]  [<c0128ba9>] ? printk+0x1a/0x1c
[    4.060000]  [<c015d7f1>] register_tracer+0xc8/0x14f
[    4.060000]  [<c08803fc>] init_irqsoff_tracer+0xd/0x11
[    4.060000]  [<c010104f>] do_one_initcall+0x4f/0x130
[    4.060000]  [<c08803ef>] ? init_irqsoff_tracer+0x0/0x11
[    4.060000]  [<c0121390>] ? wake_up_process+0xf/0x11
[    4.060000]  [<c0134ab2>] ? start_workqueue_thread+0x22/0x25
[    4.060000]  [<c0134d99>] ? __create_workqueue_key+0xa9/0x141
[    4.060000]  [<c086c5c3>] kernel_init+0x17b/0x1e2
[    4.060000]  [<c086c448>] ? kernel_init+0x0/0x1e2
[    4.060000]  [<c0104ab3>] kernel_thread_helper+0x7/0x10
[    4.060000]  =======================
[    4.064053] PASSED
[    4.066133] initcall init_irqsoff_tracer+0x0/0x11 returned 0 after 15 msecs
[    4.068005] calling  init_wakeup_tracer+0x0/0xf @ 1

	Ingo
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