From: John Levon <levon@movementarian.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Mike Kravetz <kravetz@us.ibm.com>,
phil.el@wanadoo.fr, Ingo Molnar <mingo@elte.hu>,
linux-kernel@vger.kernel.org,
oprofile-list@lists.sourceforge.net
Subject: Re: oprofile can cause an NMI to schedule (was: [RT] scheduling and oprofile)
Date: Tue, 24 Oct 2006 13:46:50 +0100 [thread overview]
Message-ID: <20061024124650.GA2668@totally.trollied.org> (raw)
In-Reply-To: <1161656674.13276.17.camel@localhost.localdomain>
On Mon, Oct 23, 2006 at 10:24:34PM -0400, Steven Rostedt wrote:
> > caller is rt_mutex_slowlock+0x156/0x1dd
> > [<c032051a>] schedule+0x65/0xd2 (8)
> > [<c0321338>] rt_mutex_slowlock+0x156/0x1dd (12)
> > [<c032142a>] rt_mutex_lock+0x24/0x28 (72)
> > [<c0134904>] rt_down_read+0x38/0x3b (20)
> > [<c0322a89>] do_page_fault+0xe3/0x52d (12)
> > [<c03229a6>] do_page_fault+0x0/0x52d (76)
> > [<c01033bb>] error_code+0x4f/0x54 (8)
> > [<c01ce6d0>] __copy_from_user_ll+0x55/0x7c (44)
> > [<f89be7ef>] dump_user_backtrace+0x2e/0x56 [oprofile] (24)
> > [<c0134869>] rt_up_read+0x3e/0x41 (20)
> > [<f89be864>] x86_backtrace+0x4a/0x5a [oprofile] (20)
> > [<f89bd53a>] oprofile_add_sample+0x73/0x89 [oprofile] (20)
> > [<f89beea3>] athlon_check_ctrs+0x22/0x4a [oprofile] (32)
> > [<f89be8c5>] nmi_callback+0x18/0x1b [oprofile] (28)
> > [<c01041ff>] do_nmi+0x24/0x33 (12)
> > [<c0103462>] nmi_stack_correct+0x1d/0x22 (16)
> >
> > It seems strange to me that oprofile would be calling
> > '__copy_from_user_ll' in this context. I can see why the
> > changes made for RT locking expose this. But, doesn't this
> > issue also exist on non-RT (default) kernels? What happens
> > when we generate a page fault in this context on non-RT kernels?
> >
>
> As Mike has pointed out here, oprofile _can_ cause the nmi to schedule.
in_atomic() is supposed to be true in this context, so the test in
do_page_fault() catches it.
john
next prev parent reply other threads:[~2006-10-24 12:46 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-10-23 21:23 [RT] scheduling and oprofile Mike Kravetz
2006-10-24 2:24 ` oprofile can cause an NMI to schedule (was: [RT] scheduling and oprofile) Steven Rostedt
2006-10-24 12:46 ` John Levon [this message]
2006-10-24 12:54 ` Steven Rostedt
2006-10-25 18:58 ` Mike Kravetz
2006-10-25 19:52 ` Lee Revell
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