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    SubjectRe: [patch 2/5] signalfd v2 - signalfd core ...
    Davide Libenzi wrote:
    >
    > +int signalfd_deliver(struct sighand_struct *sighand, int sig, struct siginfo *info)
    > +{
    > + int nsig = 0;
    > + struct list_head *pos;
    > + struct signalfd_ctx *ctx;
    > + struct signalfd_sq *sq;
    > +
    > + list_for_each(pos, &sighand->sfdlist) {
    > + ctx = list_entry(pos, struct signalfd_ctx, lnk);
    > + /*
    > + * We use a negative signal value as a way to broadcast that the
    > + * sighand has been orphaned, so that we can notify all the
    > + * listeners about this.
    > + */
    > + if (sig < 0)
    > + __wake_up_locked(&ctx->wqh, TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE);
    > + else if (sigismember(&ctx->sigmask, sig) &&
    > + (sig >= SIGRTMIN || !sigismember(&ctx->pending, sig))) {
    > + sigaddset(&ctx->pending, sig);

    I don't understand the "(sig >= SIGRTMIN || !sigismember(&ctx->pending, sig))"
    check. This mimics the LEGACY_QUEUE() check, but seems strange. The signal may
    be pending in ctx->pending just because it was not signalfd_fetchsig()ed, yes?

    Please also see below.

    > +asmlinkage long sys_signalfd(int ufd, sigset_t __user *user_mask, size_t sizemask)
    > +{
    >
    > [...snip...]
    >
    > + } else {
    > + error = -EBADF;
    > + file = fget(ufd);
    > + if (!file)
    > + goto err_exit;
    > + ctx = file->private_data;
    > + error = -EINVAL;
    > + if (file->f_op != &signalfd_fops) {
    > + fput(file);
    > + goto err_exit;
    > + }
    > + spin_lock_irq(&ctx->sighand->siglock);
    > + ctx->sigmask = sigmask;
    > + spin_unlock_irq(&ctx->sighand->siglock);
    > + wake_up(&ctx->wqh);

    Can't this race with sys_signalfd_dequeue() which use lockless __add_wait_queue()?
    Looks like we should do __wake_up_locked() under ctx->sighand->siglock.

    > --- linux-2.6.20.ep2.orig/kernel/signal.c 2007-03-07 15:55:43.000000000 -0800
    > +++ linux-2.6.20.ep2/kernel/signal.c 2007-03-07 15:59:01.000000000 -0800
    >
    > [...snip...]
    >
    > @@ -780,6 +785,11 @@
    > BUG_ON(!irqs_disabled());
    > assert_spin_locked(&t->sighand->siglock);
    >
    > + /*
    > + * Deliver the signal to listening signalfds ...
    > + */
    > + signalfd_notify(t->sighand, sig, info);
    > +
    > /* Short-circuit ignored signals. */
    > if (sig_ignored(t, sig))
    > goto out;
    > @@ -968,6 +978,11 @@
    > assert_spin_locked(&p->sighand->siglock);
    > handle_stop_signal(sig, p);
    >
    > + /*
    > + * Deliver the signal to listening signalfds ...
    > + */
    > + signalfd_notify(p->sighand, sig, info);
    > +
    > /* Short-circuit ignored signals. */
    > if (sig_ignored(p, sig))
    > return ret;

    It is strange that we are doing signalfd_notify() even if the signal is ignored.
    Isn't it better to shift signalfd_notify() into send_signal() ? This way we do
    not need the special check in signalfd_deliver() above.

    Also, this patch doesn't take send_sigqueue/send_group_sigqueue into account.

    Oleg.

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