Messages in this thread | | | From | "BALBIR SINGH" <> | Subject | [RFC] down and down_interruptible on x86 | Date | Thu, 13 Jun 2002 10:47:00 +0530 |
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Hello, All,
I am a little confused about down and down_interruptible. My mixed mind tells me it might be a bug in __down() and __down_interruptible()
snippet from semaphore.c
int __down_interruptible(struct semaphore * sem) { ....
/* * With signals pending, this turns into * the trylock failure case - we won't be * sleeping, and we* can't get the lock as * it has contention. Just correct the count * and exit. */ if (signal_pending(current)) { retval = -EINTR; sem->sleepers = 0; atomic_add(sleepers, &sem->count); break; } .....
spin_unlock_irq(&semaphore_lock); tsk->state = TASK_RUNNING; remove_wait_queue(&sem->wait, &wait); wake_up(&sem->wait); <--------------------- Is this correct? return retval; }
Lets assume that two processes/threads called down_interruptible on a semaphore.
P1 P2 --- ---
down_interruptible() down_interruptible() | | V V Did not get semaphore, so signals pending, so leave (break in the signal_pending if) waits in the wait queue | | V V schedule() Remove self from wait_queue | V Call wake_up on &sem->wait
Wont wake_up(&sem->wait), wakeup p1, so then when up() is called for waking up P1, the system will panic.
Am I missing something?
Warm Regards, Balbir
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