Hi Andrew,
On Thursday 10 May 2007 07:20, you wrote:
> On Wed, 9 May 2007 14:13:27 +0530 Sripathi Kodi <[email protected]>
wrote:
<snip old patch>
> Your changelogs aren't vey logical. The context for this change is off in
>
> a different patch. I reproduce it here:
> > I am trying to fix the BUG I mentioned here:
> > http://lkml.org/lkml/2007/04/20/41. I noticed that an elegant way to
> > solve this problem is to have a write_trylock_irqsave helper function.
> > Since we don't have this now, the code in ptrace_attach implements it
> > using local_irq_disable and write_trylock. I wish to add
> > write_trylock_irqsave to mainline kernel and then fix the -rt specific
> > problem using this.
>
> I can't imagine why -rt's write_unlock_irq() doesn't do local_irq_enable().
>
> I have no problem adding write_trylock_irqsave() - it fills a gap in the
> API.
>
> Once we have write_trylock_irqsave() it makes sense to use it here.
>
> One the downside, we added a few bytes to the SMP kernel, which I guess we
> can live with.
>
> Whether this change is desired in -rt I don't know. Ingo?
>
> I don't think the initialisation of `flags' there was needed?
I removed the initialization of 'flags' in the following patch. Would you like
to drop the old one and pick up this?
Signed-off-by: Sripathi Kodi <[email protected]>
diff -uprN linux-2.6.21.1_org/kernel/ptrace.c linux-2.6.21.1/kernel/ptrace.c
--- linux-2.6.21.1_org/kernel/ptrace.c 2007-05-09 13:18:39.000000000 +0530
+++ linux-2.6.21.1/kernel/ptrace.c 2007-05-10 17:40:51.000000000 +0530
@@ -160,6 +160,7 @@ int ptrace_may_attach(struct task_struct
int ptrace_attach(struct task_struct *task)
{
int retval;
+ unsigned long flags;
retval = -EPERM;
if (task->pid <= 1)
@@ -178,9 +179,7 @@ repeat:
* cpu's that may have task_lock).
*/
task_lock(task);
- local_irq_disable();
- if (!write_trylock(&tasklist_lock)) {
- local_irq_enable();
+ if (!write_trylock_irqsave(&tasklist_lock, flags)) {
task_unlock(task);
do {
cpu_relax();
@@ -208,7 +207,7 @@ repeat:
force_sig_specific(SIGSTOP, task);
bad:
- write_unlock_irq(&tasklist_lock);
+ write_unlock_irqrestore(&tasklist_lock, flags);
task_unlock(task);
out:
return retval;
-
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