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Message-ID: <470F40C4.1050901@freedesktop.org>
Date: Fri, 12 Oct 2007 02:39:16 -0700
From: Josh Triplett <josh@...edesktop.org>
To: ego@...ibm.com
CC: Paul E McKenney <paulmck@...ibm.com>, linux-kernel@...r.kernel.org,
Andrew Morton <akpm@...ux-foundation.org>,
Oleg Nesterov <oleg@...sign.ru>,
Dipankar Sarma <dipankar@...ibm.com>, rostedt@...dmis.org
Subject: Re: [PATCH] Use raw_smp_processor_id() in rcu_random()
Gautham R Shenoy wrote:
> With CONFIG_PREEMPT=y on 2.6.23-rc8-mm2, rcu_random() calls
> smp_processor_id() from a preemptible context, triggering the
> following kernel error.
>
> BUG: using smp_processor_id() in preemptible [00000001] code: rcu_torture_fak/5155
> caller is rcu_random+0x16/0x39 [rcutorture]
> [<c010612f>] dump_trace+0x68/0x1d2
> [<c01062b1>] show_trace_log_lvl+0x18/0x2c
> [<c0106c23>] show_trace+0xf/0x11
> [<c0106d33>] dump_stack+0x12/0x14
> [<c02a0a25>] debug_smp_processor_id+0xa1/0xb4
> [<f887064c>] rcu_random+0x16/0x39 [rcutorture]
> [<f8870cdf>] <3>BUG: using smp_processor_id() in preemptible [00000001] code: rcu_torture_fak/5156
> rcu_torture_fakewriter+0x4d/0xc5 [rcutorture]
> [<c0139b32>] caller is rcu_random+0x16/0x39 [rcutorture]
> kthread+0x38/0x5e
> [<c0105ca7>] kernel_thread_helper+0x7/0x10
> =======================
> [<c010612f>] dump_trace+0x68/0x1d2
> [<c01062b1>] show_trace_log_lvl+0x18/0x2c
> [<c0106c23>] show_trace+0xf/0x11
> [<c0106d33>] dump_stack+0x12/0x14
> [<c02a0a25>] debug_smp_processor_id+0xa1/0xb4
> [<f887064c>] rcu_random+0x16/0x39 [rcutorture]
> [<f8870cdf>] rcu_torture_fakewriter+0x4d/0xc5 [rcutorture]
>
> rcu_random() can do with raw_smp_processor_id() as a parameter to cpu_clock()
> in this particular context.
>
> Signed-off-by: Gautham R Shenoy <ego@...ibm.com>
Looks reasonable to me.
Acked-by: Josh Triplett <josh@...nel.org>
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