From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752452Ab0CRQ4Q (ORCPT ); Thu, 18 Mar 2010 12:56:16 -0400 Received: from mail-pv0-f174.google.com ([74.125.83.174]:43234 "EHLO mail-pv0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751089Ab0CRQ4O (ORCPT ); Thu, 18 Mar 2010 12:56:14 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=xjI59TN19puWVH7hcMja+/d9uUSO65Erj6ERgabQanLynpF/s2pvnBLvTbvMMkQoLl 9GjqFg8VBz70HZ/kmYPcJ+OnWBDWEhEPA1SrrT62/ilVwkZXpu2zdxVGWqN2NLlP7qYA YMfLcvyvze35U039ENcNZNf8upIl1Qr/r9XmA= Date: Thu, 18 Mar 2010 17:56:16 +0100 From: Frederic Weisbecker To: Li Zefan Cc: David Miller , sparclinux@vger.kernel.org, tj@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [BUG] percpu misaligned allocation Message-ID: <20100318165613.GA5103@nowhere> References: <20100318044930.GC5045@nowhere> <20100317.232648.59697287.davem@davemloft.net> <4BA1CA91.2060004@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4BA1CA91.2060004@cn.fujitsu.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 18, 2010 at 02:39:13PM +0800, Li Zefan wrote: > David Miller wrote: > > From: Frederic Weisbecker > > 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? > > > > Yes, it's expanded by some crazy macro in include/trace/ftrace.h.. > > In linus' tree, it's called ftrace_profile_lock_acquire(), and it's > renamed to perf_trace_lock_acquire() in -tip tree by commit > 97d5a22005f38057b4bc0d95f81cd26510268794. > > #undef DECLARE_EVENT_CLASS > #define DECLARE_EVENT_CLASS(call, proto, args, tstruct, assign, print) \ > static notrace void \ > ftrace_profile_templ_##call(struct ftrace_event_call *event_call, \ > proto) \ > { \ > struct ftrace_data_offsets_##call __maybe_unused __data_offsets;\ > struct ftrace_raw_##call *entry; \ > u64 __addr = 0, __count = 1; \ > unsigned long irq_flags; \ > int __entry_size; \ > int __data_size; \ > int rctx; \ > \ > ... > } Yeah indeed. The problem happens in Linus's tree and -tip tree as well, it's just that I debugged it in -tip and there has been a naming change inside, I forgot about that. So in mainline the problem happens in ftrace_profile_templ_lock_acquire (macro generated above). Thanks.