linux-kernel - Re: [PATCH V2 2/3] riscv: Add support for restartable sequence

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Date:   Mon, 19 Jul 2021 10:43:10 -0400 (EDT)
From:   Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:     Vincent Chen <vincent.chen@...ive.com>,
        Guo Ren <guoren@...ux.alibaba.com>
Cc:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        linux-kselftest <linux-kselftest@...r.kernel.org>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH V2 2/3] riscv: Add support for restartable sequence

----- On Mar 9, 2020, at 1:59 AM, Vincent Chen vincent.chen@...ive.com wrote:
[...]
> --- a/arch/riscv/kernel/signal.c
> +++ b/arch/riscv/kernel/signal.c
> @@ -234,6 +234,7 @@ static void handle_signal(struct ksignal *ksig, struct
> pt_regs *regs)
> 	sigset_t *oldset = sigmask_to_save();
> 	int ret;
> 
> +	rseq_signal_deliver(ksig, regs);
> 	/* Are we from a system call? */
> 	if (regs->cause == EXC_SYSCALL) {

[...]

As Al Viro pointed out on IRC, the rseq_signal_deliver() should go after syscall
restart handling, similarly to what is done on every other supported architecture.

Note that there is already an upstream commit derived on this non-upstream patch:

commit 9866d141a097 ("csky: Add support for restartable sequence")

which is broken in the same way.

I'm not sure why I was never CC'd on the csky patch. Considering that nobody
bothered to implement the rseq selftests for csky, I don't see how any of
this is tested. I would favor a revert of that commit until the testing glue
is contributed. Unfortunately, the csky commit has been upstream since v5.7.

Thanks,

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com