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    SubjectRe: [PATCH RESEND 1/2] tracing: syscall_*regfunc() can race with copy_process()
    On Thu, 10 Apr 2014 15:34:35 +0200
    Oleg Nesterov <oleg@redhat.com> wrote:

    > On 04/10, Steven Rostedt wrote:
    > >
    > > On Wed, 9 Apr 2014 19:05:42 +0200
    > > Oleg Nesterov <oleg@redhat.com> wrote:
    > >
    > > > --- a/kernel/fork.c
    > > > +++ b/kernel/fork.c
    > > > @@ -1472,7 +1472,9 @@ static struct task_struct *copy_process(unsigned long clone_flags,
    > > >
    > > > total_forks++;
    > > > spin_unlock(&current->sighand->siglock);
    > > > + syscall_tracepoint_update(p);
    > > > write_unlock_irq(&tasklist_lock);
    > > > +
    > >
    > > So this looks to be a fix that probably should go to stable?
    >
    > Not sure, this is up to you.

    I'll have to think about this one, whether or not it should go to
    stable.

    >
    > > > @@ -732,33 +732,31 @@ static int sys_tracepoint_refcount;
    > > >
    > > > void syscall_regfunc(void)
    > > > {
    > > > - unsigned long flags;
    > > > struct task_struct *g, *t;
    > > >
    > > > if (!sys_tracepoint_refcount) {
    > > > - read_lock_irqsave(&tasklist_lock, flags);
    > > > + read_lock(&tasklist_lock);
    > > > do_each_thread(g, t) {
    > > > /* Skip kernel threads. */
    > > > - if (t->mm)
    > > > + if (!(t->flags & PF_KTHREAD))
    > > > set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
    > > > } while_each_thread(g, t);
    > > > - read_unlock_irqrestore(&tasklist_lock, flags);
    > > > + read_unlock(&tasklist_lock);
    > > > }
    > > > sys_tracepoint_refcount++;
    > > > }
    > > >
    > > > void syscall_unregfunc(void)
    > > > {
    > > > - unsigned long flags;
    > > > struct task_struct *g, *t;
    > > >
    > > > sys_tracepoint_refcount--;
    > > > if (!sys_tracepoint_refcount) {
    > > > - read_lock_irqsave(&tasklist_lock, flags);
    > > > + read_lock(&tasklist_lock);
    > > > do_each_thread(g, t) {
    > > > clear_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
    > > > } while_each_thread(g, t);
    > > > - read_unlock_irqrestore(&tasklist_lock, flags);
    > > > + read_unlock(&tasklist_lock);
    > >
    > > These changes should be in a separate patch, as they can wait till 3.16.
    >
    > OK, I'll split this change.

    Are you going to send a new series?

    -- Steve



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