linux-kernel - Re: [PATCH 0/4] [GIT PULL] tracing: recursion and compile fixes

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Date:	Mon, 20 Apr 2009 21:48:54 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 0/4] [GIT PULL] tracing: recursion and compile fixes

On Mon, Apr 20, 2009 at 03:43:21PM -0400, Steven Rostedt wrote:
> 
> On Mon, 20 Apr 2009, Ingo Molnar wrote:
> > Running tests on all trace events:
> > Testing all events: <4>Tracing recursion: HC[0]:SC[0]:NMI[0]
> 
> Recursion is wrong :-/
> 
> > ------------[ cut here ]------------
> > WARNING: at kernel/trace/ring_buffer.c:1510 ring_buffer_lock_reserve+0xf7/0x1ce()
> > Hardware name: To Be Filled By O.E.M.
> > Pid: 1, comm: swapper Not tainted 2.6.30-rc2-tip-01538-ge8201b9-dirty #37740
> > Call Trace:
> >  <IRQ>  [<ffffffff80268a01>] warn_slowpath+0xcc/0x114
> >  [<ffffffff80299ed3>] ? trace_hardirqs_on_caller+0x11d/0x179
> >  [<ffffffff80299ba6>] ? mark_held_locks+0x60/0x95
> >  [<ffffffff802ca335>] ring_buffer_lock_reserve+0xf7/0x1ce
> >  [<ffffffff802ceb60>] trace_buffer_lock_reserve+0x34/0x7e
> >  [<ffffffff810c8f97>] ? do_IRQ+0xf/0xe8
> >  [<ffffffff802cf949>] trace_current_buffer_lock_reserve+0x36/0x4c
> >  [<ffffffff802d9da4>] function_test_events_call+0x7e/0xe2
> >  [<ffffffff80216313>] ? ret_from_intr+0x0/0x16
> >  [<ffffffff80215616>] ftrace_call+0x5/0x2b
> >  [<ffffffff8021630e>] ? common_interrupt+0xe/0x13
> >  [<ffffffff810c8f9c>] ? do_IRQ+0x14/0xe8
> 
> The function tracer was called before we updated the hardirq_count :-/



Oh! I feared about such racy situation. That's really a pity, this context count
is so useful :-/

Frederic.


 
> I liked the fact that we can detect same level recursion. Perhaps I'll 
> just make a depth test instead. Have a max of 16? times we can recurse 
> (should be plenty) and then bug if we hit it?
> 
> -- Steve
> 
> 
> >  [<ffffffff8021630e>] ? common_interrupt+0xe/0x13
> >  [<ffffffff80216313>] ret_from_intr+0x0/0x16
> >  <EOI>  [<ffffffff802c311c>] ? trace_clock_local+0x37/0x57
> >  [<ffffffff80254b27>] ? __wake_up+0x57/0x7a
> >  [<ffffffff802c9e60>] ? rb_reserve_next_event+0x73/0x319
> >  [<ffffffff802f6106>] ? ftrace_raw_event_kmalloc+0x11/0xdd
> >  [<ffffffff802d0ac8>] ? trace_wake_up+0x41/0x57
> >  [<ffffffff802ca3ab>] ? ring_buffer_lock_reserve+0x16d/0x1ce
> >  [<ffffffff802ceb60>] ? trace_buffer_lock_reserve+0x34/0x7e
> >  [<ffffffff802c278d>] ? tracepoint_entry_add_probe+0xb3/0x12b
> >  [<ffffffff802c278d>] ? tracepoint_entry_add_probe+0xb3/0x12b
> >  [<ffffffff802cf949>] ? trace_current_buffer_lock_reserve+0x36/0x4c
> >  [<ffffffff802c278d>] ? tracepoint_entry_add_probe+0xb3/0x12b
> >  [<ffffffff802f615d>] ? ftrace_raw_event_kmalloc+0x68/0xdd
> >  [<ffffffff802c278d>] ? tracepoint_entry_add_probe+0xb3/0x12b
> >  [<ffffffff8031e265>] ? __kmalloc+0x268/0x298
> >  [<ffffffff802969c6>] ? ftrace_event_lock_acquire+0x0/0x89
> >  [<ffffffff802c278d>] ? tracepoint_entry_add_probe+0xb3/0x12b
> >  [<ffffffff802c1e5f>] ? get_tracepoint+0x12/0x274
> >  [<ffffffff802969c6>] ? ftrace_event_lock_acquire+0x0/0x89
> >  [<ffffffff802c2875>] ? tracepoint_add_probe+0x70/0xf6
> >  [<ffffffff802c2cf0>] ? tracepoint_probe_register+0x40/0xbc
> >  [<ffffffff802968dd>] ? ftrace_reg_event_lock_acquire+0x2b/0x5c
> >  [<ffffffff802d886f>] ? ftrace_event_enable_disable+0x43/0x59
> >  [<ffffffff802d8cb4>] ? ftrace_set_clr_event+0x10c/0x15b
> >  [<ffffffff81b70aa3>] ? event_trace_self_tests+0x39b/0x3e6
> >  [<ffffffff81b70c52>] ? event_trace_self_tests_init+0x0/0x5f
> >  [<ffffffff81b70c8d>] ? event_trace_self_tests_init+0x3b/0x5f
> >  [<ffffffff8020a0b6>] ? do_one_initcall+0x84/0x1ad
> >  [<ffffffff8029c513>] ? __lock_acquire+0x851/0x8d3
> >  [<ffffffff8037d3de>] ? get_inode_number+0x61/0xc2
> >  [<ffffffff8037d4f1>] ? proc_register+0xb2/0x139
> >  [<ffffffff8037d553>] ? proc_register+0x114/0x139
> >  [<ffffffff8021df9e>] ? native_sched_clock+0x25/0x9c
> >  [<ffffffff8021df73>] ? sched_clock+0x33/0x39
> >  [<ffffffff80297ccf>] ? lock_release_holdtime+0x2f/0x19d
> >  [<ffffffff8037d553>] ? proc_register+0x114/0x139
> >  [<ffffffff8029d44b>] ? __lock_release+0x177/0x196
> >  [<ffffffff8037d4f1>] ? proc_register+0xb2/0x139
> >  [<ffffffff80637f3e>] ? _raw_spin_unlock+0x14f/0x16e
> >  [<ffffffff810c7e43>] ? _spin_unlock+0x3a/0x55
> >  [<ffffffff8037d553>] ? proc_register+0x114/0x139
> >  [<ffffffff8037d6de>] ? create_proc_entry+0x92/0xbe
> >  [<ffffffff802b95a1>] ? register_irq_proc+0xc2/0xf2
> >  [<ffffffff81b53140>] ? early_idt_handler+0x0/0x71
> >  [<ffffffff81b53140>] ? early_idt_handler+0x0/0x71
> >  [<ffffffff81b53aa8>] ? kernel_init+0xb2/0x11a
> >  [<ffffffff81b53140>] ? early_idt_handler+0x0/0x71
> >  [<ffffffff80216a4a>] ? child_rip+0xa/0x20
> >  [<ffffffff802163d0>] ? restore_args+0x0/0x30
> >  [<ffffffff81b539f6>] ? kernel_init+0x0/0x11a
> >  [<ffffffff80216a40>] ? child_rip+0x0/0x20
> > ---[ end trace 0d52030ff90bb47d ]---

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