From: Paolo Bonzini <pbonzini@redhat.com>
To: Peter Xu <peterx@redhat.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
stable@vger.kernel.org
Subject: Re: [PATCH] KVM: selftests: Always run vCPU thread with blocked SIG_IPI
Date: Tue, 20 Apr 2021 18:24:50 +0200 [thread overview]
Message-ID: <84c52ebe-58a2-6188-270e-c86409e44fa3@redhat.com> (raw)
In-Reply-To: <20210420153223.GB4440@xz-x1>
On 20/04/21 17:32, Peter Xu wrote:
> On Tue, Apr 20, 2021 at 10:37:39AM -0400, Peter Xu wrote:
>> On Tue, Apr 20, 2021 at 04:16:14AM -0400, Paolo Bonzini wrote:
>>> The main thread could start to send SIG_IPI at any time, even before signal
>>> blocked on vcpu thread. Therefore, start the vcpu thread with the signal
>>> blocked.
>>>
>>> Without this patch, on very busy cores the dirty_log_test could fail directly
>>> on receiving a SIGUSR1 without a handler (when vcpu runs far slower than main).
>>>
>>> Reported-by: Peter Xu <peterx@redhat.com>
>>> Cc: stable@vger.kernel.org
>>> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>>
>> Yes, indeed better! :)
>>
>> Reviewed-by: Peter Xu <peterx@redhat.com>
>
> I just remembered one thing: this will avoid program quits, but still we'll get
> the signal missing.
In what sense the signal will be missing? As long as the thread exists,
the signal will be accepted (but not delivered because it is blocked);
it will then be delivered on the first KVM_RUN.
Paolo
From that pov I slightly prefer the old patch. However
> not a big deal so far as only dirty ring uses SIG_IPI, so there's always ring
> full which will just delay the kick. It's just we need to remember this when we
> extend IPI to non-dirty-ring tests as the kick is prone to be lost then.
>
> Thanks,
>
next prev parent reply other threads:[~2021-04-20 16:24 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-20 8:16 [PATCH] KVM: selftests: Always run vCPU thread with blocked SIG_IPI Paolo Bonzini
2021-04-20 14:37 ` Peter Xu
2021-04-20 15:32 ` Peter Xu
2021-04-20 16:24 ` Paolo Bonzini [this message]
2021-04-20 16:58 ` Peter Xu
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