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[Wetek.Play/amlkernel] - fix race condition in ge2d_wq.

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1. thread 1 is here https://github.com/codesnake/linux-amlogic/blob/master/drivers/amlogic/display/ge2d/ge2d_wq.c#L147
2. thread 2 is here https://github.com/codesnake/linux-amlogic/blob/master/drivers/amlogic/display/ge2d/ge2d_wq.c#L855
3. thread 2 is running and enters the if condition because state is GE2D_STATE_RUNNING
4. thread 2 gets interrupted by thread 1 thread 1 jumps over the if and sets GE2D_STATE_IDLE and is done
5. back to thread 2 which now sets state GE2D_STATE_REMOVING_WQ and calls wait_for_completion
6. thread2 will never return because thread 1 is done already and won't signal the event

destroy_ge2d_work_queue is called from https://github.com/codesnake/linux-amlogic/blob/master/drivers/amlogic/amports/amvideocap.c#L320 in my use case and will block there forever - and basically blocks down to the read in the userspace which tries to read the current captured frame
This commit is contained in:
Memphiz 2015-01-15 09:41:17 +01:00 committed by Memphis
parent 14592b4cd3
commit d12146f9e4
1 changed files with 53 additions and 0 deletions
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53
projects/WeTek_Play/patches/linux/80-ge2d-fix-ge2d_state-race.patch Normal file
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@ -0,0 +1,53 @@
--- a/include/linux/amlogic/ge2d/ge2d_wq.h 2015-01-14 00:46:24.916408987 +0100
+++ b/include/linux/amlogic/ge2d/ge2d_wq.h 2015-01-14 00:45:24.233715480 +0100
@@ -81,6 +81,7 @@
ge2d_event_t event ;
int irq_num;
int ge2d_state;
+ spinlock_t state_lock; //for sync access to ge2d_state
int process_queue_state;
}ge2d_manager_t ;
--- a/drivers/amlogic/display/ge2d/ge2d_wq.c 2015-01-14 00:59:18.775744127 +0100
+++ b/drivers/amlogic/display/ge2d/ge2d_wq.c 2015-01-14 00:58:59.440160948 +0100
@@ -144,9 +144,11 @@
}while(pos!=head);
ge2d_manager.last_wq=wq;
exit:
+ spin_lock(&ge2d_manager.state_lock);
if(ge2d_manager.ge2d_state==GE2D_STATE_REMOVING_WQ)
- complete(&ge2d_manager.event.process_complete);
+ complete(&ge2d_manager.event.process_complete);
ge2d_manager.ge2d_state=GE2D_STATE_IDLE;
+ spin_unlock(&ge2d_manager.state_lock);
return ret;
}
@@ -854,8 +856,17 @@
spin_unlock(&ge2d_manager.event.sem_lock);
if((ge2d_manager.current_wq==ge2d_work_queue)&&(ge2d_manager.ge2d_state== GE2D_STATE_RUNNING))
{
- ge2d_manager.ge2d_state=GE2D_STATE_REMOVING_WQ;
- wait_for_completion(&ge2d_manager.event.process_complete);
+ // check again with lock
+ int wasRunning = 0;
+ spin_lock(&ge2d_manager.state_lock);
+ if (ge2d_manager.ge2d_state== GE2D_STATE_RUNNING)
+ {
+ ge2d_manager.ge2d_state=GE2D_STATE_REMOVING_WQ;
+ wasRunning = 1;
+ }
+ spin_unlock(&ge2d_manager.state_lock);
+ if (wasRunning)
+ wait_for_completion(&ge2d_manager.event.process_complete);
ge2d_manager.last_wq=NULL; //condition so complex ,simplify it .
}//else we can delete it safely.
@@ -902,6 +913,7 @@
//prepare bottom half
spin_lock_init(&ge2d_manager.event.sem_lock);
+ spin_lock_init(&ge2d_manager.state_lock);
sema_init (&ge2d_manager.event.cmd_in_sem,1);
init_waitqueue_head (&ge2d_manager.event.cmd_complete);
init_completion(&ge2d_manager.event.process_complete);