linux-kernel - Re: Random scheduler/unaligned accesses crashes with perf lock events on sparc 64

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Message-Id: <20100405.122233.188421941.davem@davemloft.net>
Date:	Mon, 05 Apr 2010 12:22:33 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	fweisbec@...il.com
Cc:	sparclinux@...r.kernel.org, linux-kernel@...r.kernel.org,
	mingo@...e.hu, acme@...hat.com, a.p.zijlstra@...llo.nl,
	paulus@...ba.org
Subject: Re: Random scheduler/unaligned accesses crashes with perf lock
 events on sparc 64

From: Frederic Weisbecker <fweisbec@...il.com>
Date: Mon, 5 Apr 2010 08:57:04 +0200

> It seems to happen after an unaligned access fixup.

You shouldn't be getting the unaligned fixup in the first place,
especially in the locations where you see them.  I suspect that
once you see first fixup, all of the registers in the cpu have
been corrupted in one way or another.

I suspect something fundamental gets corrupted, for example the
current register window (%cwp) is corrupted and that screws up all of
the registers so every single function starts accessing garbage.

My suspicions lie in three places, the ftrace mcount()
stubs, stack_trace_flush(), or the new perf_arch_save_caller_regs()
since those are the three places offhand that could make
us potentially make us return to function in the wrong
register window.
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