On Mon, Apr 09, 2012 at 11:40:31AM +0300, Pekka Enberg wrote:
On Mon, 2012-04-09 at 03:38 +0400, Anton Vorontsov wrote:
vmevent grabs a mutex in the atomic context, and so this pops up:
BUG: sleeping function called from invalid context at kernel/mutex.c:271 in_atomic(): 1, irqs_disabled(): 0, pid: 0, name: swapper/0
[...]
This patch fixes the issue by removing the mutex and making the logic lock-free.
Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org
What guarantees that there's only one thread writing to struct vmevent_attr::value in vmevent_sample() now that the mutex is gone?
Well, it is called from the timer function, which has the same guaranties as an interrupt handler: it can have only one execution thread (unlike bare softirq handler), so we don't need to worry about racing w/ ourselves?
If you're concerned about several instances of timers accessing the same vmevent_watch, I don't really see how it is possible, as we allocate vmevent_watch together w/ the timer instance in vmevent_fd(), so there is always one timer per vmevent_watch.
Thanks,