Re: [PATCH] riscv: don't stop itself in smp_send_stop

From: Andreas Schwab <schwab@suse.de>
To: Atish Patra <atish.patra@wdc.com>
Cc: "linux-riscv@lists.infradead.org" <linux-riscv@lists.infradead.org>
Subject: Re: [PATCH] riscv: don't stop itself in smp_send_stop
Date: Mon, 10 Dec 2018 11:58:12 +0100	[thread overview]
Message-ID: <mvmsgz5bqd7.fsf@suse.de> (raw)
In-Reply-To: <72991c58-91f5-abb1-54f9-35ae4533a26e@wdc.com> (Atish Patra's message of "Thu, 29 Nov 2018 10:52:40 -0800")

On Nov 29 2018, Atish Patra <atish.patra@wdc.com> wrote:

>> +	cpumask_copy (&mask, cpu_online_mask);
>> +	cpumask_clear_cpu (smp_processor_id (), &mask);
>> +	on_each_cpu_mask(&mask, ipi_stop, NULL, 0);
>
> The function header of on_each_cpu_mask says func should be
> non-blocking. Not sure if that's a hard requirement or not.

What does that mean?

>> +
>> +	/* Wait up to one second for other CPUs to stop */
>> +	timeout = USEC_PER_SEC;
>> +	while (num_online_cpus() > 1 && timeout--)
>> +		udelay(1);
>> +
>> +	if (num_online_cpus() > 1)
>> +		pr_warn("SMP: failed to stop secondary CPUs\n");
>
> May be print the remaining online cpus so that we know which one failed ?

I have copied that from arm.  The only user of smp_send_stop is panic,
which can cope with that, and the probability of that happening is very
low anyway.

Andreas.

-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
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