A couple of very minor nits,
> +static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, siginfo_t *info,
> + int nonblock)
> +{
> + int locked;
> + ssize_t ret;
> + struct signalfd_lockctx lk;
> + DECLARE_WAITQUEUE(wait, current);
> +
> + locked = signalfd_lock(ctx, &lk);
> + if (!locked)
> + return 0;
> +
> + ret = dequeue_signal(lk.tsk, &ctx->sigmask, info);
> + switch (ret) {
> + case 0:
> + if (!nonblock)
> + break;
> + ret = -EAGAIN;
> + default:
> + signalfd_unlock(&lk);
> + return ret;
> + }
> +
> + add_wait_queue(&ctx->wqh, &wait);
> + for (;;) {
> + set_current_state(TASK_INTERRUPTIBLE);
> + ret = dequeue_signal(lk.tsk, &ctx->sigmask, info);
> + if (ret != 0)
> + break;
> + if (signal_pending(current)) {
> + ret = -ERESTARTSYS;
> + break;
> + }
> + signalfd_unlock(&lk);
The locking looks a bit overcomplicated. We don't need signalfd_lock() to
check ret != 0 or signal_pending(), we can drop it earlier. This way we
always leave the loop in "unlocked" state.
> + schedule();
> + locked = signalfd_lock(ctx, &lk);
> + if (unlikely(!locked)) {
> + /*
> + * Let the caller read zero byte, ala socket
> + * recv() when the peer disconnect. This test
> + * must be done before doing a dequeue_signal(),
> + * because if the sighand has been orphaned,
> + * the dequeue_signal() call is going to crash.
> + */
Imho, the comment is a bit confusing. dequeue_signal() needs ->siglock
even if signalfd_ctx is not orphaned.
> + ret = 0;
> + break;
> + }
> + }
> +
> + remove_wait_queue(&ctx->wqh, &wait);
> + __set_current_state(TASK_RUNNING);
> +
> + if (likely(locked))
> + signalfd_unlock(&lk);
> +
> + return ret;
> +}
IOW, how about this?
static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, siginfo_t *info,
int nonblock)
{
ssize_t ret;
struct signalfd_lockctx lk;
DECLARE_WAITQUEUE(wait, current);
if (!signalfd_lock(ctx, &lk))
return 0;
ret = dequeue_signal(lk.tsk, &ctx->sigmask, info);
switch (ret) {
case 0:
if (!nonblock)
break;
ret = -EAGAIN;
default:
signalfd_unlock(&lk);
return ret;
}
add_wait_queue(&ctx->wqh, &wait);
for (;;) {
set_current_state(TASK_INTERRUPTIBLE);
ret = dequeue_signal(lk.tsk, &ctx->sigmask, info);
signalfd_unlock(&lk);
if (ret != 0)
break;
ret = -ERESTARTSYS;
if (signal_pending(current))
break;
schedule();
ret = 0;
if (!signalfd_lock(ctx, &lk))
break;
}
remove_wait_queue(&ctx->wqh, &wait);
__set_current_state(TASK_RUNNING);
return ret;
}
Oleg.
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