From: Ingo Molnar <mingo@elte.hu>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>,
Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] tracing/function-graph-tracer: strip ending newlines on comments
Date: Tue, 23 Dec 2008 09:18:55 +0100 [thread overview]
Message-ID: <20081223081855.GA6009@elte.hu> (raw)
In-Reply-To: <20081223064804.GA24956@elte.hu>
btw., ftrace_printk() is not NMI safe:
x
BUG: spinlock recursion on CPU#1, loop_yield/3360
lock: ffffffff807a0c60, .magic: dead4ead, .owner: loop_yield/3360, .owner_cpu: 1
Pid: 3360, comm: loop_yield Not tainted 2.6.28-rc9-tip #48
Call Trace:
<NMI> [<ffffffff8038ba23>] spin_bug+0xa2/0xaa
[<ffffffff8038baf8>] _raw_spin_lock+0x42/0x134
[<ffffffff8059f0fc>] _spin_lock_irqsave+0x44/0x50
[<ffffffff802890c4>] ? trace_vprintk+0x8e/0x164
[<ffffffff8059eeea>] ? _spin_unlock_irqrestore+0x3d/0x4c
[<ffffffff802890c4>] trace_vprintk+0x8e/0x164
[<ffffffff802182a6>] ? __hw_perf_counter_set_period+0x1ed/0x280
[<ffffffff802892ef>] __ftrace_printk+0x55/0x57
[<ffffffff802182cc>] __hw_perf_counter_set_period+0x213/0x280
[<ffffffff80218d8c>] __smp_perf_counter_interrupt+0x21c/0x3c2
[<ffffffff805a043a>] perf_counter_nmi_handler+0x35/0x3f
[<ffffffff805a1cc9>] notifier_call_chain+0x5e/0x92
[<ffffffff805a1d5b>] __atomic_notifier_call_chain+0x5e/0x87
[<ffffffff805a1cfd>] ? __atomic_notifier_call_chain+0x0/0x87
[<ffffffff805a1d93>] atomic_notifier_call_chain+0xf/0x11
[<ffffffff80258e9d>] notify_die+0x2e/0x30
[<ffffffff8059fdd2>] do_nmi+0x9f/0x25f
[<ffffffff8059f7fa>] nmi+0x1a/0x2c
[<ffffffff80287104>] ? __rb_reserve_next+0x4b/0x3c8
[<ffffffff802871dd>] ? __rb_reserve_next+0x124/0x3c8
<<EOE>> <IRQ> [<ffffffff80287628>] rb_reserve_next_event+0x1a7/0x307
[<ffffffff8028796c>] ring_buffer_lock_reserve+0x8b/0xd3
[<ffffffff8028910b>] trace_vprintk+0xd5/0x164
[<ffffffff80260fb3>] ? trace_hardirqs_on_caller+0xfd/0x138
[<ffffffff8028dd2b>] ? __perf_counter_remove_from_context+0x60/0x179
[<ffffffff802892ef>] __ftrace_printk+0x55/0x57
[<ffffffff802180a6>] ? pmc_generic_disable+0x266/0x279
[<ffffffff8028dd59>] __perf_counter_remove_from_context+0x8e/0x179
[<ffffffff8026835d>] generic_smp_call_function_single_interrupt+0x87/0xc0
[<ffffffff8021fd8d>] smp_call_function_single_interrupt+0x24/0x34
[<ffffffff8020d053>] call_function_single_interrupt+0x13/0x20
<EOI>
caused by:
spin_lock_irqsave(&trace_buf_lock, irq_flags);
which locking is necessiated by:
static DEFINE_SPINLOCK(trace_buf_lock);
static char trace_buf[TRACE_BUF_SIZE];
i think this should be changed to a PER_CPU data structure - and if an NMI
context mixes up the buffer, that's not a big issue. (i'd not complicate
it by using a NMI specific buffer)
Ingo
next prev parent reply other threads:[~2008-12-23 8:19 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-12-22 18:16 [PATCH] tracing/function-graph-tracer: strip ending newlines on comments Frederic Weisbecker
2008-12-23 6:48 ` Ingo Molnar
2008-12-23 8:18 ` Ingo Molnar [this message]
2008-12-23 12:31 ` Frédéric Weisbecker
2008-12-23 12:14 ` Frédéric Weisbecker
2008-12-23 12:18 ` Ingo Molnar
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