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Message-ID: <20070726073520.GA12206@elte.hu>
Date: Thu, 26 Jul 2007 09:35:20 +0200
From: Ingo Molnar <mingo@...e.hu>
To: Ankita Garg <ankita@...ibm.com>
Cc: Arjan van de Ven <arjan@...radead.org>, linux@...mer.net,
LKML <linux-kernel@...r.kernel.org>,
RT-Users <linux-rt-users@...r.kernel.org>,
mathieu.desnoyers@...ymtl.ca
Subject: Re: [Question] Hooks for scheduler tracing (CFS)
* Ankita Garg <ankita@...ibm.com> wrote:
> The probe point did get triggered, and soon after that I had the
> following in dmesg, leading to system hang...
>
> BUG: scheduling while atomic: softirq-rcu/3/0x00000004/52, CPU#3
>
> Call Trace:
> <#DB> [<ffffffff81033555>] __schedule_bug+0x4b/0x4f
> [<ffffffff8128b414>] __sched_text_start+0xcc/0xaaa
> [<ffffffff8100b574>] dump_trace+0x248/0x25d
> [<ffffffff81068334>] print_traces+0x9/0xb
> [<ffffffff8100b5e5>] show_trace+0x5c/0x64
> [<ffffffff8128c1c2>] schedule+0xe4/0x104
> [<ffffffff8128d10c>] rt_spin_lock_slowlock+0xfc/0x19e
> [<ffffffff8128d9de>] __rt_spin_lock+0x1f/0x21
> [<ffffffff8128d9e9>] rt_spin_lock+0x9/0xb
> [<ffffffff88387dcc>]
> :stap_c1a10b1292b5f87a563f56d89ddfc765_606:_stp_print_flush+0x5f/0xdf
> [<ffffffff88389e41>]
> :stap_c1a10b1292b5f87a563f56d89ddfc765_606:probe_1493+0x1f6/0x257
> [<ffffffff8838bdc3>]
I'd suggest to not put a probe into a preempt-off section - put it to
the beginning and to the end of schedule() to capture context-switches.
_stp_print_flush() is in the systemtap-generated module, right? Maybe
the problem is resolved by changing that spinlock to use raw_spinlock_t
/ DEFINE_RAW_SPIN_LOCK.
Ingo
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