On 08/27/2011 01:54 PM, Michael Büsch wrote:
On Sat, 27 Aug 2011 13:26:00 -0500
Larry Finger<Larry.Finger@xxxxxxxxxxxx> wrote:
CHECK drivers/net/wireless/b43/main.c
drivers/net/wireless/b43/main.c +4115 b43_wireless_core_stop(7) warn: variable dereferenced before check 'dev'
This is next material.
-next, just because the bug is not in the current kernel?
Or because you think this is harmless?
I'm not sure whether this is harmless. It effectively is that kind
of bug that triggers dangerous compiler optimizations.
I think the compiler has some freedom to assume dev can not be NULL when
the function is entered and thus optimize out the !dev check.
No, the check has to be left in due to the changing of dev in the routine
followed by a 'goto redo'.
According to 'git blame', the commit that added the part that swatch does not
like was
36dbd954 (Michael Buesch 2009-09-04 22:51:29 +0200 4115)
That was when the branch back to redo was added. As your comment says
* Returns the current dev. This might be different from the passed in dev,
* because the core might be gone away while we unlocked the mutex. */
In fact, a bug in the original code is unlikely, but my patch did add one. I
think the code should be
if (!dev)
return NULL;
wl = dev->wl;
redo:
That should work correctly and satisfy swatch. Would that do too much damage to
the compiler's optimization?
Larry
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