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From: Thomas Gleixner <tglx@linutronix.de>
To: "Jürgen Groß" <jgross@suse.com>, LKML <linux-kernel@vger.kernel.org>
Cc: x86@kernel.org, Boris Ostrovsky <boris.ostrovsky@oracle.com>,
	Stefano Stabellini <sstabellini@kernel.org>,
	xen-devel@lists.xenproject.org
Subject: Re: [PATCH] xen: Enable interrupts when calling _cond_resched()
Date: Wed, 19 Feb 2020 15:53:11 +0100	[thread overview]
Message-ID: <87h7zmpr1k.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <8808612b-11c2-f7b8-f027-7ff92e992c50@suse.com>

Jürgen Groß <jgross@suse.com> writes:

> On 19.02.20 12:01, Thomas Gleixner wrote:
>> xen_maybe_preempt_hcall() is called from the exception entry point
>> xen_do_hypervisor_callback with interrupts disabled.
>> 
>> _cond_resched() evades the might_sleep() check in cond_resched() which
>> would have caught that and schedule_debug() unfortunately lacks a check
>> for irqs_disabled().
>> 
>> Enable interrupts around the call and use cond_resched() to catch future
>> issues.
>> 
>> Fixes: fdfd811ddde3 ("x86/xen: allow privcmd hypercalls to be preempted")
>> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
>> ---
>>   drivers/xen/preempt.c |    4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>> 
>> --- a/drivers/xen/preempt.c
>> +++ b/drivers/xen/preempt.c
>> @@ -33,8 +33,10 @@ asmlinkage __visible void xen_maybe_pree
>>   		 * cpu.
>>   		 */
>>   		__this_cpu_write(xen_in_preemptible_hcall, false);
>> -		_cond_resched();
>> +		local_irq_enable();
>> +		cond_resched();
>>   		__this_cpu_write(xen_in_preemptible_hcall, true);
>> +		local_irq_disable();
>
> Could you please put the call of local_irq_disable() directly after the
> cond_resched() call to make the result symmetric regarding writing of
> xen_in_preemptible_hcall and irq enable/disable?

Darn. Of course does this need to be there. Stupid me, let me resend.

WARNING: multiple messages have this Message-ID (diff)
From: Thomas Gleixner <tglx@linutronix.de>
To: "Jürgen Groß" <jgross@suse.com>, LKML <linux-kernel@vger.kernel.org>
Cc: xen-devel@lists.xenproject.org,
	Boris Ostrovsky <boris.ostrovsky@oracle.com>,
	x86@kernel.org, Stefano Stabellini <sstabellini@kernel.org>
Subject: Re: [Xen-devel] [PATCH] xen: Enable interrupts when calling _cond_resched()
Date: Wed, 19 Feb 2020 15:53:11 +0100	[thread overview]
Message-ID: <87h7zmpr1k.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <8808612b-11c2-f7b8-f027-7ff92e992c50@suse.com>

Jürgen Groß <jgross@suse.com> writes:

> On 19.02.20 12:01, Thomas Gleixner wrote:
>> xen_maybe_preempt_hcall() is called from the exception entry point
>> xen_do_hypervisor_callback with interrupts disabled.
>> 
>> _cond_resched() evades the might_sleep() check in cond_resched() which
>> would have caught that and schedule_debug() unfortunately lacks a check
>> for irqs_disabled().
>> 
>> Enable interrupts around the call and use cond_resched() to catch future
>> issues.
>> 
>> Fixes: fdfd811ddde3 ("x86/xen: allow privcmd hypercalls to be preempted")
>> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
>> ---
>>   drivers/xen/preempt.c |    4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>> 
>> --- a/drivers/xen/preempt.c
>> +++ b/drivers/xen/preempt.c
>> @@ -33,8 +33,10 @@ asmlinkage __visible void xen_maybe_pree
>>   		 * cpu.
>>   		 */
>>   		__this_cpu_write(xen_in_preemptible_hcall, false);
>> -		_cond_resched();
>> +		local_irq_enable();
>> +		cond_resched();
>>   		__this_cpu_write(xen_in_preemptible_hcall, true);
>> +		local_irq_disable();
>
> Could you please put the call of local_irq_disable() directly after the
> cond_resched() call to make the result symmetric regarding writing of
> xen_in_preemptible_hcall and irq enable/disable?

Darn. Of course does this need to be there. Stupid me, let me resend.

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  reply	other threads:[~2020-02-19 14:53 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-19 11:01 [PATCH] xen: Enable interrupts when calling _cond_resched() Thomas Gleixner
2020-02-19 11:01 ` [Xen-devel] " Thomas Gleixner
2020-02-19 12:02 ` Jürgen Groß
2020-02-19 12:02   ` [Xen-devel] " Jürgen Groß
2020-02-19 14:53   ` Thomas Gleixner [this message]
2020-02-19 14:53     ` Thomas Gleixner
2020-02-19 17:30     ` [PATCH V2] " Thomas Gleixner
2020-02-19 17:30       ` [Xen-devel] " Thomas Gleixner
2020-02-19 18:42       ` Jürgen Groß
2020-02-19 18:42         ` [Xen-devel] " Jürgen Groß

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