ChangeSet 1.1587.3.49, 2004/05/11 15:45:25-07:00, oliver@neukum.org
[PATCH] USB: fixes of assumptions about waitqueues
quoting Linus:
--
> so there is no need to recheck the bit in do/while loop, because
> there is no false wakeups now.
You should never assume this. You should assume that there are _always_
false wakeups.
Why? Because Linux has always allowed people to leave wait-queues active,
without being "atomic". For example, the tty read/write layer used to
(still does?) add itself on the wait-queue _once_, and then leave itself
on the wait-queue while in a loop it does copies from/to user space.
--
Unfortunately, this means us. Here's the first fix. Comments?
- make sure timeouts are observed even if somebody left us on a queue
drivers/usb/image/mdc800.c | 12 +++++++++---
1 files changed, 9 insertions(+), 3 deletions(-)
diff -Nru a/drivers/usb/image/mdc800.c b/drivers/usb/image/mdc800.c
--- a/drivers/usb/image/mdc800.c Fri May 14 15:28:47 2004
+++ b/drivers/usb/image/mdc800.c Fri May 14 15:28:47 2004
@@ -319,7 +319,9 @@
set_current_state(TASK_INTERRUPTIBLE);
if (!mdc800->irq_woken)
{
- schedule_timeout (msec*HZ/1000);
+ long timeout = msec*HZ/1000;
+ while(timeout)
+ timeout = schedule_timeout (timeout);
}
remove_wait_queue(&mdc800->irq_wait, &wait);
set_current_state(TASK_RUNNING);
@@ -718,7 +720,9 @@
set_current_state(TASK_INTERRUPTIBLE);
if (!mdc800->downloaded)
{
- schedule_timeout (TO_DOWNLOAD_GET_READY*HZ/1000);
+ long timeout = TO_DOWNLOAD_GET_READY*HZ/1000;
+ while(timeout)
+ timeout = schedule_timeout (timeout);
}
set_current_state(TASK_RUNNING);
remove_wait_queue(&mdc800->download_wait, &wait);
@@ -842,7 +846,9 @@
set_current_state(TASK_INTERRUPTIBLE);
if (!mdc800->written)
{
- schedule_timeout (TO_WRITE_GET_READY*HZ/1000);
+ long timeout = TO_WRITE_GET_READY*HZ/1000;
+ while(timeout)
+ timeout = schedule_timeout (timeout);
}
set_current_state(TASK_RUNNING);
remove_wait_queue(&mdc800->write_wait, &wait);