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Date:   Thu, 8 Oct 2020 16:21:35 +0200
From:   Oleg Nesterov <oleg@redhat.com>
To:     Jens Axboe <axboe@kernel.dk>
Cc:     linux-kernel@vger.kernel.org, io-uring@vger.kernel.org,
        peterz@infradead.org, tglx@linutronix.de
Subject: Re: [PATCH 3/6] kernel: split syscall restart from signal handling
Message-ID: <20201008142135.GH9995@redhat.com>
References: <20201005150438.6628-1-axboe@kernel.dk>
 <20201005150438.6628-4-axboe@kernel.dk>
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On 10/05, Jens Axboe wrote:
>
> Move the restart syscall logic into a separate generic entry helper,
> and handle that part separately from signal checking and delivery.
>
> This is in preparation for being able to do syscall restarting
> independently from handling signals.
>
> Signed-off-by: Jens Axboe <axboe@kernel.dk>
> ---
>  arch/x86/kernel/signal.c     | 32 ++++++++++++++++++--------------
>  include/linux/entry-common.h | 14 ++++++++++++--
>  kernel/entry/common.c        | 11 ++++++++---
>  3 files changed, 38 insertions(+), 19 deletions(-)

Can't we avoid this patch and the and simplify the change in
exit_to_user_mode_loop() from the next patch? Can't the much more simple
patch below work?

Then later we can even change arch_do_signal() to accept the additional
argument, ti_work, so that it can use ti_work & TIF_NOTIFY_SIGNAL/SIGPENDING
instead of test_thread_flag/task_sigpending.

Oleg.

--- x/arch/x86/kernel/signal.c
+++ x/arch/x86/kernel/signal.c
@@ -808,7 +808,10 @@ void arch_do_signal(struct pt_regs *regs
 {
 	struct ksignal ksig;
 
-	if (get_signal(&ksig)) {
+	if (test_thread_flag(TIF_NOTIFY_SIGNAL))
+		tracehook_notify_signal();
+
+	if (task_sigpending(current) && get_signal(&ksig)) {
 		/* Whee! Actually deliver the signal.  */
 		handle_signal(&ksig, regs);
 		return;
--- x/kernel/entry/common.c
+++ x/kernel/entry/common.c
@@ -155,7 +155,7 @@ static unsigned long exit_to_user_mode_l
 		if (ti_work & _TIF_PATCH_PENDING)
 			klp_update_patch_state(current);
 
-		if (ti_work & _TIF_SIGPENDING)
+		if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)
 			arch_do_signal(regs);
 
 		if (ti_work & _TIF_NOTIFY_RESUME) {