On Wed, 9 May 2007 14:13:27 +0530 Sripathi Kodi <[email protected]> wrote:
> Hi,
>
> This patch makes ptrace_attach use write_trylock_irqsave.
>
> Signed-off-by: Sripathi Kodi <[email protected]>
>
> ---
> kernel/ptrace.c | 7 +++----
> 1 files changed, 3 insertions(+), 4 deletions(-)
>
> Index: linux-2.6.21/kernel/ptrace.c
> ===================================================================
> --- linux-2.6.21.orig/kernel/ptrace.c
> +++ linux-2.6.21/kernel/ptrace.c
> @@ -160,6 +160,7 @@ int ptrace_may_attach(struct task_struct
> int ptrace_attach(struct task_struct *task)
> {
> int retval;
> + unsigned long flags = 0;
>
> 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;
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?
-
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