Commit Graph

3 Commits

Author SHA1 Message Date
Paul Jackson
2efe86b809 [PATCH] cpuset exit NULL dereference fix
There is a race in the kernel cpuset code, between the code
to handle notify_on_release, and the code to remove a cpuset.
The notify_on_release code can end up trying to access a
cpuset that has been removed.  In the most common case, this
causes a NULL pointer dereference from the routine cpuset_path.
However all manner of bad things are possible, in theory at least.

The existing code decrements the cpuset use count, and if the
count goes to zero, processes the notify_on_release request,
if appropriate.  However, once the count goes to zero, unless we
are holding the global cpuset_sem semaphore, there is nothing to
stop another task from immediately removing the cpuset entirely,
and recycling its memory.

The obvious fix would be to always hold the cpuset_sem
semaphore while decrementing the use count and dealing with
notify_on_release.  However we don't want to force a global
semaphore into the mainline task exit path, as that might create
a scaling problem.

The actual fix is almost as easy - since this is only an issue
for cpusets using notify_on_release, which the top level big
cpusets don't normally need to use, only take the cpuset_sem
for cpusets using notify_on_release.

This code has been run for hours without a hiccup, while running
a cpuset create/destroy stress test that could crash the existing
kernel in seconds.  This patch applies to the current -linus
git kernel.

Signed-off-by: Paul Jackson <pj@sgi.com>
Acked-by: Simon Derr <simon.derr@bull.net>
Acked-by: Dinakar Guniguntala <dino@in.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-05-27 08:07:26 -07:00
Benoit Boissinot
9a8488965d [PATCH] cpuset: remove function attribute const
gcc-4 warns with
include/linux/cpuset.h:21: warning: type qualifiers ignored on function
return type

cpuset_cpus_allowed is declared with const
extern const cpumask_t cpuset_cpus_allowed(const struct task_struct *p);

First const should be __attribute__((const)), but the gcc manual
explains that:

"Note that a function that has pointer arguments and examines the data
pointed to must not be declared const. Likewise, a function that calls a
non-const function usually must not be const. It does not make sense for
a const function to return void."

The following patch remove const from the function declaration.

Signed-off-by: Benoit Boissinot <benoit.boissinot@ens-lyon.org>
Acked-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-04-16 15:25:59 -07:00
Linus Torvalds
1da177e4c3 Linux-2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!
2005-04-16 15:20:36 -07:00