lkml.org 
[lkml]   [2002]   [Sep]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: Sleeping function called from illegal context...
On Sat, Sep 28, 2002 at 02:27:44PM -0400, Robert Love wrote:

> > NMI interrupt handler cannot block so it trylocks against a spinlock
> > instead. Buffer processing code needs to block against concurrent NMI
> > interrupts so takes the spinlock for them. All actual blocks on the
> > spinlock are beneath a down() on another semaphore, so a sleep whilst
> > holding the spinlock won't actually cause deadlock.
>
> If all accesses to the spinlock are taken under a semaphore, then the
> spinlock is not needed (i.e. the down'ed semaphore provides the same
> protection), or am I missing something?
>
> If this is not the case - e.g. there are other accesses to these locks -
> then you cannot sleep, no?

The other accessors are spin_trylock()ers, as I mentioned. They will not
block but they are not under the semaphore.

The spinlock cannot be a semaphore because NMI interrupts do not take to
kindly to up()

regards
john

--
"When your name is Winner, that's it. You don't need a nickname."
- Loser Lane
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:29    [W:0.799 / U:0.556 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site