Use ERESTART_RESTARTBLOCK if poll() is interrupted by a signal (3075d9da) · Commits · 戴 / test

Lomesh reported poll returning EINTR during suspend/resume cycle. This is caused by the STOP/CONT cycle that the freezer uses, generating a pending signal for what in effect is an ignored signal. In general poll is a little eager in returning EINTR, when it could try not bother userspace and simply restart the syscall. Both select and ppoll do use ERESTARTNOHAND to restart the syscall. Oleg points out that simply using ERESTARTNOHAND will cause poll to restart with original timeout value. which could ultimately lead to process never returning to userspace. Instead use ERESTART_RESTARTBLOCK, and restart poll with updated timeout value. Inspired by Manfred's use ERESTARTNOHAND in poll patch. [bunk@kernel.org: do_restart_poll() can become static] Cc: Manfred Spraul <manfred@colorfullife.com> Cc: Oleg Nesterov <oleg@tv-sign.ru> Cc: Roland McGrath <roland@redhat.com> Cc: "Agarwal, Lomesh" <lomesh.agarwal@intel.com> Signed-off-by:

Chris Wright <chrisw@sous-sol.org> Signed-off-by:

Adrian Bunk <bunk@kernel.org> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

fs/select.c

+30 −1

Original line number	Diff line number	Diff line
		@@ -714,10 +714,28 @@ out_fds:
		return err;
		}

		static long do_restart_poll(struct restart_block *restart_block)
		{
		struct pollfd __user ufds = (struct pollfd __user)restart_block->arg0;
		int nfds = restart_block->arg1;
		s64 timeout = ((s64)restart_block->arg3<<32) \| (s64)restart_block->arg2;
		int ret;

		ret = do_sys_poll(ufds, nfds, &timeout);
		if (ret == -EINTR) {
		restart_block->fn = do_restart_poll;
		restart_block->arg2 = timeout & 0xFFFFFFFF;
		restart_block->arg3 = (u64)timeout >> 32;
		ret = -ERESTART_RESTARTBLOCK;
		}
		return ret;
		}

		asmlinkage long sys_poll(struct pollfd __user *ufds, unsigned int nfds,
		long timeout_msecs)
		{
		s64 timeout_jiffies;
		int ret;

		if (timeout_msecs > 0) {
		#if HZ > 1000
		@@ -732,7 +750,18 @@ asmlinkage long sys_poll(struct pollfd __user *ufds, unsigned int nfds,
		timeout_jiffies = timeout_msecs;
		}

		return do_sys_poll(ufds, nfds, &timeout_jiffies);
		ret = do_sys_poll(ufds, nfds, &timeout_jiffies);
		if (ret == -EINTR) {
		struct restart_block *restart_block;
		restart_block = &current_thread_info()->restart_block;
		restart_block->fn = do_restart_poll;
		restart_block->arg0 = (unsigned long)ufds;
		restart_block->arg1 = nfds;
		restart_block->arg2 = timeout_jiffies & 0xFFFFFFFF;
		restart_block->arg3 = (u64)timeout_jiffies >> 32;
		ret = -ERESTART_RESTARTBLOCK;
		}
		return ret;
		}

		#ifdef TIF_RESTORE_SIGMASK

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