Hi,
[CC: list reduced as starting a new thread, most on the context
removed as this concern a different issue.]
On Tue, Nov 16, 2010 at 7:16 PM, Grant Likely <grant.likely@xxxxxxxxxxxx> wrote:
> On Tue, Nov 16, 2010 at 3:41 PM, <dirk.brandewie@xxxxxxxxx> wrote:
>> From: Dirk Brandewie <dirk.brandewie@xxxxxxxxx>
>> [...]
> The kernel needs to complain *loudly* if this occurs because it
> represents a bug. I'm tempted to say use BUG, but that would halt the
> kernel and prevent any possibility of kernel log output.
> [...]
does it ? if CONFIG_BUG is not enabled and the arch has no define for
it, the default does _nothing_:
from `include/asm-generic/bug.h':
#else /* !CONFIG_BUG */
#ifndef HAVE_ARCH_BUG
#define BUG() do {} while(0)
#endif
#ifndef HAVE_ARCH_BUG_ON
#define BUG_ON(condition) do { if (condition) ; } while(0)
#endif
[...]
gcc is triggering about ~30 warnings (like [0]) on code path using
BUG(). Most of these path assume BUG() will never return, which is not
true.
The commit message introducing this behavior state:
commit c8538a7aa5527d02c7191ac5da124efadf6a2827
Author: Matt Mackall <mpm@xxxxxxxxxxx>
Date: Sun May 1 08:59:01 2005 -0700
[PATCH] remove all kernel BUGs
This patch eliminates all kernel BUGs, trims about 35k off the typical
kernel, and makes the system slightly faster.
Signed-off-by: Matt Mackall <mpm@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxx>
[...]
+config BUG
+ bool "BUG() support" if EMBEDDED
+ default y
+ help
+ Disabling this option eliminates support for BUG and WARN, reducing
+ the size of your kernel image and potentially quietly ignoring
+ numerous fatal conditions. You should only consider disabling this
+ option for embedded systems with no facilities for reporting errors.
So how should BUG() been used ?
1) assuming it will never _ever_ return ?
2) assuming it may return ?
if (1), its definition has to be changed, if (2) a lot of path have to be fixed.
Thanks in advance,
- Arnaud
[0]: fs/dcache.c:1899:1: warning: control reaches end of non-void
function, line match an old revision, but the BUG() is still there.
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