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From: Steven Rostedt <rostedt@goodmis.org>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
	Andrew Morton <akpm@linux-foundation.org>,
	David Miller <davem@davemloft.net>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Rusty Russell <rusty@rustcorp.com.au>
Subject: Re: [PATCH 2/2] Tracepoints: Fix section alignment using pointer array
Date: Wed, 02 Feb 2011 13:47:17 -0500	[thread overview]
Message-ID: <1296672437.10797.60.camel@gandalf.stny.rr.com> (raw)
In-Reply-To: <20110202183138.GB27022@Krystal>

On Wed, 2011-02-02 at 13:31 -0500, Mathieu Desnoyers wrote:
> * Steven Rostedt (rostedt@goodmis.org) wrote:
> > From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> > 
> > Make the tracepoints more robust, making them solid enough to handle compiler
> > changes by not relying on anything based on compiler-specific behavior with
> > respect to structure alignment. Implement an approach proposed by David Miller:
> > use an array of const pointers to refer to the individual structures, and export
> > this pointer array through the linker script rather than the structures per se.
> > It will consume 32 extra bytes per tracepoint (24 for structure padding and 8
> > for the pointers), but are less likely to break due to compiler changes.
> > 
> > History:
> > 
> > commit 7e066fb870fcd1025ec3ba7bbde5d541094f4ce1 added the aligned(32) type and
> > variable attribute to the tracepoint structures to deal with gcc happily
> > aligning statically defined structures on 32-byte multiples.
> > 
> > commit 15e3540ce2159705f18fad6147ffedf04445ad64 tried to use a 8-byte alignment
> > for tracepoint structures by applying both the variable and type attribute to
> > tracepoint structures definitions and declarations. It worked fine with gcc
> > 4.5.1, but broke with gcc 4.4.4 and 4.4.5.
> 
> Small nit: this reference to commit 15e3540ce2159705f18fad6147ffedf04445ad64
> should be changed to a non-commit-id-related explanation, because the commit has
> been rolled back from -tip.

Yeah, I noticed this too, right after I posted it.

> 
> The rest looks good.

OK, I'll rebase by just removing the reverted commit reference.

Thanks,

-- Steve



  reply	other threads:[~2011-02-02 18:47 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-02-02 18:06 [PATCH 0/2] [GIT PULL][v2.6.38]: tracing: alignment fixes (take 2) Steven Rostedt
2011-02-02 18:06 ` [PATCH 1/2] tracing: Replace trace_event struct array with pointer array Steven Rostedt
2011-02-02 18:42   ` Mathieu Desnoyers
2011-02-02 18:53     ` Steven Rostedt
2011-02-02 22:50   ` David Miller
2011-02-03  0:46     ` Steven Rostedt
2011-02-03  0:49       ` David Miller
2011-02-02 18:06 ` [PATCH 2/2] Tracepoints: Fix section alignment using " Steven Rostedt
2011-02-02 18:31   ` Mathieu Desnoyers
2011-02-02 18:47     ` Steven Rostedt [this message]
2011-02-02 18:56     ` Steven Rostedt
2011-02-02 19:32       ` Mathieu Desnoyers
2011-02-02 22:20       ` Thomas Gleixner
2011-02-03  0:43         ` Steven Rostedt
2011-02-02 22:51   ` David Miller
2011-02-03  0:44 ` [PATCH 0/2] [GIT PULL][v2.6.38]: tracing: alignment fixes (take 2) Steven Rostedt

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