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Date: Tue, 11 Nov 2008 10:09:15 +0100
From: Ingo Molnar <mingo@...e.hu>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
Andrew Morton <akpm@...ux-foundation.org>,
Steven Rostedt <srostedt@...hat.com>
Subject: Re: [PATCH 2/2] ring-buffer: replace most bug ons with warn on and
disable buffer
* Steven Rostedt <rostedt@...dmis.org> wrote:
> +#define RB_WARN_ON_RET_INT(buffer, cond) \
> + do { \
> + if (unlikely(cond)) { \
> + atomic_inc(&buffer->record_disabled); \
> + WARN_ON(1); \
> return -1; \
> } \
btw., the _RET() methods are rather ugly as they include an implicit
code flow change (a 'return' statement).
Please change it to a more readable form that preserves the code flow,
something like:
if (RB_WARN_ON(buffer, cond))
return -1;
See kernel/lockdep.c about how to do this cleanly: introduce a
_single_ global "oh, we are broken" flag which is increased once and
never decreased again.
In the case of lockdep that's the debug_locks flag. It's used in
various code-flow-preserving forms of debug checks:
...
if (DEBUG_LOCKS_WARN_ON(depth >= 20))
return;
...
if (!debug_locks_off_graph_unlock())
return NULL;
...
if (!debug_locks_off_graph_unlock())
return 0;
...
if (!__raw_spin_is_locked(&lockdep_lock))
return DEBUG_LOCKS_WARN_ON(1);
etc.
Ingo
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