linux-kernel - Re: [BUG] percpu misaligned allocation

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Message-Id: <20100317.232648.59697287.davem@davemloft.net>
Date:	Wed, 17 Mar 2010 23:26:48 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	fweisbec@...il.com
Cc:	sparclinux@...r.kernel.org, tj@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [BUG] percpu misaligned allocation

From: Frederic Weisbecker <fweisbec@...il.com>
Date: Thu, 18 Mar 2010 05:49:33 +0100

> While using the lock events through perf in a sparc box, I can see
> the following message repeated many times:
> 
> 	Kernel unaligned access at TPC[49357c] perf_trace_lock_acquire+0xb4/0x180
> 
> It actually hangs the box as the messages are sent to a serial console.
> 
> When used with perf, the trace events use a per cpu buffer allocated
> in kernel/trace/trace_event_perf.c, and the allocation appears to return
> a misaligned percpu pointer. It is aligned to 4 while it seems it
> requires to be aligned to 8.

Thanks I'll take a look at this.

RAW locks (both rwlocks and spinlocks) on sparc64 are 4-bytes
in size, maybe some piece of code is assuming that locks
are cpu word sized.

Where is perf_trace_lock_acquire() I can't find it in Linus's
tree?  Does it get created by some crazy macro expansion?

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