From: Steven Rostedt <rostedt@goodmis.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>,
Ingo Molnar <mingo@elte.hu>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] trace: disable preemption before taking raw spinlocks
Date: Tue, 26 May 2009 17:55:27 -0400 (EDT) [thread overview]
Message-ID: <alpine.DEB.2.00.0905261754380.26705@gandalf.stny.rr.com> (raw)
In-Reply-To: <1243374700.6600.26.camel@laptop>
On Tue, 26 May 2009, Peter Zijlstra wrote:
> On Tue, 2009-05-26 at 17:28 +0200, Heiko Carstens wrote:
> > From: Heiko Carstens <heiko.carstens@de.ibm.com>
> >
> > s390 code uses smp_processor_id() in __raw_spin_lock() code which
> > reveals that a (raw) spinlock is taken without preemption disabled.
> > This can potentially deadlock.
> >
> > To fix this explicitly disable and enable preemption.
> >
> > BUG: using smp_processor_id() in preemptible [00000000] code: cat/2278
> > caller is trace_find_cmdline+0x40/0xfc
> > CPU: 0 Not tainted 2.6.30-rc7-dirty #39
> > Process cat (pid: 2278, task: 000000003faedb68, ksp: 000000003b33b988)
> > 000000003b33b988 000000003b33bae0 0000000000000002 0000000000000000
> > 000000003b33bb80 000000003b33baf8 000000003b33baf8 00000000000175d6
> > 0000000000000001 000000003b33b988 000000003f9b0000 000000000000000b
> > 000000000000000c 000000003b33bb40 000000003b33bae0 0000000000000000
> > 0000000000000000 00000000000175d6 000000003b33bae0 000000003b33bb28
> > Call Trace:
> > ([<00000000000174b2>] show_trace+0x112/0x170)
> > [<0000000000017582>] show_stack+0x72/0x100
> > [<0000000000441538>] dump_stack+0xc8/0xd8
> > [<000000000025c350>] debug_smp_processor_id+0x114/0x130
> > [<00000000000bf0e4>] trace_find_cmdline+0x40/0xfc
> > [<00000000000c35d4>] trace_print_context+0x58/0xac
> > [<00000000000bb676>] print_trace_line+0x416/0x470
> > [<00000000000bc8fe>] s_show+0x4e/0x428
> > [<000000000013834e>] seq_read+0x36a/0x5d4
> > [<0000000000112a78>] vfs_read+0xc8/0x174
> > [<0000000000112c58>] SyS_read+0x74/0xc4
> > [<000000000002c7ae>] sysc_noemu+0x10/0x16
> > [<000002000012436c>] 0x2000012436c
> > 1 lock held by cat/2278:
> > #0: (&p->lock){+.+.+.}, at: [<0000000000138056>] seq_read+0x72/0x5d4
>
> Shouldn't that be preempt_disable_notrace() and co to avoid tracer
> recursion?
Doesn't need to be. That function is done in the output (slow path), not
during an actual trace.
-- Steve
next prev parent reply other threads:[~2009-05-26 21:55 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-05-26 15:28 Heiko Carstens
2009-05-26 21:51 ` Peter Zijlstra
2009-05-26 21:55 ` Steven Rostedt [this message]
2009-05-26 21:58 ` Steven Rostedt
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=alpine.DEB.2.00.0905261754380.26705@gandalf.stny.rr.com \
--to=rostedt@goodmis.org \
--cc=heiko.carstens@de.ibm.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@elte.hu \
--cc=peterz@infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®