El Wed, Mar 03, 2010 at 11:14:35AM +0530 Manish Katiyar ha dit:
> Hello all,
>
> Is the following code valid ???
>
> foo() {
> ...........
> spin_lock(lock);
> ptr = kzalloc(size, GFP_KERNEL);
> spin_unlock(lock);
> .....
> }
>
>
> I guess the answer is no, but would like to confirm. Detailed/all
> possible reasons for not doing so are welcome. IIRC, I was getting a
> kernel crash with similar code with error message as "spinlock bug :
> unlocked on wrong CPU" which looked like it was getting locked on one
> cpu and due to memory allocation was getting unlocked from another
> cpu.
preemption is disabled when a spinlock is held. memory allocation can
cause the current process to be scheduled out if the requested amount
of memory isn't available immediately, but preemption is disabled due
to the spinlock.
if you *really* need to allocate memory while holding the spinlock you
must use GFP_ATOMIC instead of GFP_KERNEL, but remember that the
allocation can fail and thus you must check the return value
best regards
--
Matthias Kaehlcke
Embedded Linux Developer
Barcelona
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one's chains, but to live in a way that
respects and enhances the freedom of others
(Nelson Mandela)
.''`.
using free software / Debian GNU/Linux | http://debian.org : :' :
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