Messages in this thread | | | Subject | Re: Lots of bugs with current->state = TASK_*INTERRUPTIBLE | From | Steven Rostedt <> | Date | Thu, 21 Jan 2010 12:31:34 -0500 |
| |
On Thu, 2010-01-21 at 11:47 +0100, Julia Lawall wrote: > What about something like the following (drivers/macintosh/adb.c): > > add_wait_queue(&state->wait_queue, &wait); > current->state = TASK_INTERRUPTIBLE; > > for (;;) { > req = state->completed; > if (req != NULL) > state->completed = req->next; > else if (atomic_read(&state->n_pending) == 0) > ret = -EIO; > if (req != NULL || ret != 0) > break; > > if (file->f_flags & O_NONBLOCK) { > ret = -EAGAIN; > break; > } > if (signal_pending(current)) { > ret = -ERESTARTSYS; > break; > } > spin_unlock_irqrestore(&state->lock, flags); > schedule(); > spin_lock_irqsave(&state->lock, flags); > } > > current->state = TASK_RUNNING; > remove_wait_queue(&state->wait_queue, &wait); > > There is a call to schedule eventually after the first current->state > assignment, but it is not right after.
I looked at this code in a bit more detail. Seems that it does not need the set_current_state(), because all activities between the state of the task and the variables being checked (state->n_pending, et al) are under the state->lock.
But there should be a comment stating that above the assignment of current->state. Something like:
/* * No need for the set_current_state() memory barrier since * all checks between state and wakeups are done under the * state->lock. */ current->state = TASK_INTERRUPTIBLE;
But I'd rather have the author of this code write that.
-- Steve
| |