From: Prarit Bhargava <prarit@redhat.com>
To: Vivek Goyal <vgoyal@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>, Jonathan Corbet <corbet@lwn.net>,
jbaron@akamai.com, kexec@lists.infradead.org,
Rusty Russell <rusty@rustcorp.com.au>,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
Fabian Frederick <fabf@skynet.be>,
isimatu.yasuaki@jp.fujitsu.com, "H. Peter Anvin" <hpa@zytor.com>,
Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
David Rientjes <rientjes@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-api@vger.kernel.org
Subject: Re: [PATCH v8] kernel, add panic_on_warn
Date: Thu, 06 Nov 2014 17:52:05 -0500 [thread overview]
Message-ID: <545BFB95.5030706@redhat.com> (raw)
In-Reply-To: <20141106220731.GA13590@redhat.com>
On 11/06/2014 05:07 PM, Vivek Goyal wrote:
> On Thu, Nov 06, 2014 at 01:57:36PM -0800, David Rientjes wrote:
>
> [..]
>> You see that doing
>>
>> if (panic_on_warn) {
>> panic_on_warn = 0;
>> panic(...);
>> }
>>
>> is racy, I hope. If two threads WARN() at the same time, then there's
>> nothing preventing a double panic() because WARN() itself is not
>> serialized against anything. So both the current comment and your
>> suggested revision comment are bogus.
>
> panic() is serialized on panic_lock. So I guess it is fine to hit WARN()
> on multiple cpus. Do you see an issue there?
Oops -- didn't see this until just now.
Once again, Vivek beat me to the punch :) and much more succinctly than I will
ever be able to do. :)
P.
>
> Thanks
> Vivek
>
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WARNING: multiple messages have this Message-ID (diff)
From: Prarit Bhargava <prarit-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
To: Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: Andi Kleen <ak-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>,
Jonathan Corbet <corbet-T1hC0tSOHrs@public.gmane.org>,
jbaron-JqFfY2XvxFXQT0dZR+AlfA@public.gmane.org,
kexec-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org,
Rusty Russell <rusty-8n+1lVoiYb80n/F98K4Iww@public.gmane.org>,
linux-doc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Fabian Frederick <fabf-AgBVmzD5pcezQB+pC5nmwQ@public.gmane.org>,
isimatu.yasuaki-+CUm20s59erQFUHtdCDX3A@public.gmane.org,
"H. Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>,
Masami Hiramatsu
<masami.hiramatsu.pt-FCd8Q96Dh0JBDgjK7y7TUQ@public.gmane.org>,
David Rientjes <rientjes-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
Andrew Morton
<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH v8] kernel, add panic_on_warn
Date: Thu, 06 Nov 2014 17:52:05 -0500 [thread overview]
Message-ID: <545BFB95.5030706@redhat.com> (raw)
In-Reply-To: <20141106220731.GA13590-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
On 11/06/2014 05:07 PM, Vivek Goyal wrote:
> On Thu, Nov 06, 2014 at 01:57:36PM -0800, David Rientjes wrote:
>
> [..]
>> You see that doing
>>
>> if (panic_on_warn) {
>> panic_on_warn = 0;
>> panic(...);
>> }
>>
>> is racy, I hope. If two threads WARN() at the same time, then there's
>> nothing preventing a double panic() because WARN() itself is not
>> serialized against anything. So both the current comment and your
>> suggested revision comment are bogus.
>
> panic() is serialized on panic_lock. So I guess it is fine to hit WARN()
> on multiple cpus. Do you see an issue there?
Oops -- didn't see this until just now.
Once again, Vivek beat me to the punch :) and much more succinctly than I will
ever be able to do. :)
P.
>
> Thanks
> Vivek
>
WARNING: multiple messages have this Message-ID (diff)
From: Prarit Bhargava <prarit@redhat.com>
To: Vivek Goyal <vgoyal@redhat.com>
Cc: David Rientjes <rientjes@google.com>,
linux-kernel@vger.kernel.org, Jonathan Corbet <corbet@lwn.net>,
Andrew Morton <akpm@linux-foundation.org>,
Rusty Russell <rusty@rustcorp.com.au>,
"H. Peter Anvin" <hpa@zytor.com>, Andi Kleen <ak@linux.intel.com>,
Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
Fabian Frederick <fabf@skynet.be>,
isimatu.yasuaki@jp.fujitsu.com, jbaron@akamai.com,
linux-doc@vger.kernel.org, kexec@lists.infradead.org,
linux-api@vger.kernel.org
Subject: Re: [PATCH v8] kernel, add panic_on_warn
Date: Thu, 06 Nov 2014 17:52:05 -0500 [thread overview]
Message-ID: <545BFB95.5030706@redhat.com> (raw)
In-Reply-To: <20141106220731.GA13590@redhat.com>
On 11/06/2014 05:07 PM, Vivek Goyal wrote:
> On Thu, Nov 06, 2014 at 01:57:36PM -0800, David Rientjes wrote:
>
> [..]
>> You see that doing
>>
>> if (panic_on_warn) {
>> panic_on_warn = 0;
>> panic(...);
>> }
>>
>> is racy, I hope. If two threads WARN() at the same time, then there's
>> nothing preventing a double panic() because WARN() itself is not
>> serialized against anything. So both the current comment and your
>> suggested revision comment are bogus.
>
> panic() is serialized on panic_lock. So I guess it is fine to hit WARN()
> on multiple cpus. Do you see an issue there?
Oops -- didn't see this until just now.
Once again, Vivek beat me to the punch :) and much more succinctly than I will
ever be able to do. :)
P.
>
> Thanks
> Vivek
>
next prev parent reply other threads:[~2014-11-06 22:52 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-05 11:42 [PATCH v8] kernel, add panic_on_warn Prarit Bhargava
2014-11-05 11:42 ` Prarit Bhargava
2014-11-05 11:42 ` Prarit Bhargava
2014-11-05 21:59 ` David Rientjes
2014-11-05 21:59 ` David Rientjes
2014-11-05 21:59 ` David Rientjes
2014-11-06 13:10 ` Prarit Bhargava
2014-11-06 13:10 ` Prarit Bhargava
2014-11-06 13:10 ` Prarit Bhargava
2014-11-06 21:57 ` David Rientjes
2014-11-06 21:57 ` David Rientjes
2014-11-06 21:57 ` David Rientjes
2014-11-06 22:07 ` Vivek Goyal
2014-11-06 22:07 ` Vivek Goyal
2014-11-06 22:07 ` Vivek Goyal
2014-11-06 22:52 ` Prarit Bhargava [this message]
2014-11-06 22:52 ` Prarit Bhargava
2014-11-06 22:52 ` Prarit Bhargava
2014-11-07 10:15 ` David Rientjes
2014-11-07 10:15 ` David Rientjes
2014-11-07 11:05 ` Prarit Bhargava
2014-11-07 11:05 ` Prarit Bhargava
2014-11-07 11:05 ` Prarit Bhargava
2014-11-07 21:09 ` David Rientjes
2014-11-07 21:09 ` David Rientjes
2014-11-08 13:29 ` Prarit Bhargava
2014-11-08 13:29 ` Prarit Bhargava
2014-11-08 13:29 ` Prarit Bhargava
2014-11-06 22:51 ` Prarit Bhargava
2014-11-06 22:51 ` Prarit Bhargava
2014-11-06 22:51 ` Prarit Bhargava
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