Hi:
It is well know that is not recomended to keep a spinlock locked during
operations that can be preempted. Some of these operations are copy_to_user,
copy_from_user.
Below is the code of the write_lock() as a sample.
340 static inline void __write_lock(rwlock_t *lock)
341{
342 preempt_disable(); <<<<<< THE ISSUE IS HERE <<<<<<<<<<<<<<
343 rwlock_acquire(&lock->dep_map, 0, 0, _RET_IP_);
344 LOCK_CONTENDED(lock, _raw_write_trylock, _raw_write_lock);
345}
On write_unlock() the preemtion is enable.
My question is: Is there any know consequence if I enable preemption before
copy_to_user/copy_from user (keeping the spinlock locked) and then disable
preemption again after the copy?????
i.e.:
write_lock(&lock);
.......
preempt_enable();
copy_to_user(.......);
preempt_disable();
.......
write_unlock(&lock);
Thanks in advance.
PAP
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