lkml.org 
[lkml]   [1999]   [Jan]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [patch] fixed both processes in D state and the /proc/ oopses [Re: [patch] Fixed the race that was oopsing Linux-2.2.0]

On Fri, 29 Jan 1999, Andrea Arcangeli wrote:

> Another way to tell the same: "how can I be sure that I am doing an
> atomic_inc(&mm->count) on a mm->count that was just > 0, and more
> important on an mm that is still allocated? "

you are misunderstanding how atomic_inc_and_test() works. The processor
guarantees this. This is the crux of SMP atomic operations. How otherwise
could we reliably build read-write spinlocks.

yes, there is no atomic_inc_and_test() yet. (it's a bit tricky to
implement but pretty much analogous to read-write locks, we probably need
to shift values down by one to get the 'just increased from -1 to 0' event
via the zero flag, and get the 'just decreased from 0 to -1' event via the
sign flag.) Also note that this is all fiction yet because we _are_
holding the kernel lock for these situations in 2.2.

-- mingo


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:50    [W:0.067 / U:0.576 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site