On 05/28, Deepa Dinamani wrote:
I agree that signal handller being called and return value not being altered is an issue with other syscalls also. I was just wondering if some userspace code assumption would be assuming this. This is not a kernel bug.
But, I do not think we have an understanding of what was wrong in 854a6ed56839a anymore since you pointed out that my assumption was not correct that the signal handler being called without errno being set is wrong.
Deepa, sorry, I simply can't parse the above... most probably because of my bad English.
One open question: this part of epoll_pwait was already broken before 854a6ed56839a. Do you agree?
if (err == -EINTR) { memcpy(¤t->saved_sigmask, &sigsaved, sizeof(sigsaved)); set_restore_sigmask(); } else set_current_blocked(&sigsaved);
I do not understand why do you think this part was broken :/
Or, I could revert the signal_pending() check and provide a fix something like below(not a complete patch)
...
-void restore_user_sigmask(const void __user *usigmask, sigset_t *sigsaved) +int restore_user_sigmask(const void __user *usigmask, sigset_t *sigsaved, int sig_pending) {
if (!usigmask) return; /* * When signals are pending, do not restore them here. * Restoring sigmask here can lead to delivering signals that the above * syscalls are intended to block because of the sigmask passed in. */
if (sig_pending) { current->saved_sigmask = *sigsaved; set_restore_sigmask(); return; }@@ -2330,7 +2330,8 @@ SYSCALL_DEFINE6(epoll_pwait, int, epfd, struct epoll_event __user *, events,
error = do_epoll_wait(epfd, events, maxevents, timeout);
restore_user_sigmask(sigmask, &sigsaved);
signal_detected = restore_user_sigmask(sigmask, &sigsaved,error == -EINTR);
I fail to understand this pseudo-code, sorry. In particular, do not understand why restore_user_sigmask() needs to return a boolean.
The only thing I _seem to_ understand is the "sig_pending" flag passed by the caller which replaces the signal_pending() check. Yes, this is what I think we should do, and this is what I tried to propose from the very beginning in my 1st email in this thread.
Oleg.