El Tue, May 22, 2007 at 09:59:01AM -0700 Arjan van de Ven ha dit:
- down_interruptible(&info->write_sem);this code is very very buggy.
+ mutex_lock_interruptible(&info->write_mtx);
#ifdef ROCKET_DEBUG_WRITE
printk(KERN_INFO "rp_write %d chars...", count);
@@ -1773,7 +1776,7 @@ end:
wake_up_interruptible(&tty->poll_wait);
#endif
}
- up(&info->write_sem);
+ mutex_unlock(&info->write_mtx);
return retval
more buggy than with the use of a semaphore?
mutex_lock_interruptible() may not get the mutex in case a signal
happens... and yet you unlox the mutex unconditionally!!!
as far as i understand only the thread that locked the mutex can
unlock it (as opposed to semaphores, which can be released by any
thread/process). obviously this doesn't make the code be more
correct. what i don't know is how the kernel behaves when
trying to unlock a mutex the thread doesn't own. another and possibly
more important problem of the code is that in case of being
interrupted by a signal the data that should be protected by the
mutex/semaphore can be accessed/changed by two threads at the same
time.
would the following resolve the problem?
if(mutex_lock_interruptible(&info->write_mtx)) return -ERESTARTSYS
thanks for your comments