Messages in this thread | | | Date | Wed, 9 May 2007 18:50:03 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH 2/2] Use write_trylock_irqsave in ptrace_attach |
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On Wed, 9 May 2007 14:13:27 +0530 Sripathi Kodi <sripathik@in.ibm.com> wrote:
> Hi, > > This patch makes ptrace_attach use write_trylock_irqsave. > > Signed-off-by: Sripathi Kodi <sripathik@in.ibm.com> > > --- > 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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