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From: Frederic Weisbecker <frederic@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: LKML <linux-kernel@vger.kernel.org>, Tejun Heo <tj@kernel.org>,
	"David S . Miller" <davem@davemloft.net>,
	Lai Jiangshan <jiangshanlai@gmail.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	"Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
	Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH 07/14] x86: Use lockdep to assert IRQs are disabled/enabled
Date: Fri, 3 Nov 2017 15:25:07 +0100	[thread overview]
Message-ID: <CAFTL4hym0k2_zOmhA+CfLodVGfuVOinPC0cK5hjTT3e0K-rhGw@mail.gmail.com> (raw)
In-Reply-To: <20171022092025.GJ6524@worktop.programming.kicks-ass.net>

2017-10-22 11:20 UTC+02:00, Peter Zijlstra <peterz@infradead.org>:
> On Fri, Oct 20, 2017 at 02:56:04AM +0200, Frederic Weisbecker wrote:
>> diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
>> index 03505ff..b4f3a55 100644
>> --- a/arch/x86/entry/common.c
>> +++ b/arch/x86/entry/common.c
>> @@ -186,7 +186,7 @@ __visible inline void prepare_exit_to_usermode(struct
>> pt_regs *regs)
>>
>>  	addr_limit_user_check();
>>
>> -	if (IS_ENABLED(CONFIG_PROVE_LOCKING) && WARN_ON(!irqs_disabled()))
>> +	if (!lockdep_assert_irqs_disabled())
>>  		local_irq_disable();
>>
>>  	lockdep_sys_exit();
>
> So this is the only site that ever uses the return value; and for this
> you've chosen the wrong value for !CONFIG_PROVE_LOCKING (namely 1),
> resulting in an unconditional CLI here for !lockdep kernels.

Hmm, it should be the opposite. The assertion maps to 1 for
!CONFIG_PROVE_LOCKING
but we are testing with "!".

> How about we replace that whole thing with a simple:
>
> 	lockdep_assert_irqs_disabled();
>
> And leave it at that, allowing us to remove the return value thing
> entirely.
>
> The whole if !disabled, disable logic is uber paranoid programming, but
> I don't think we've ever seen that WARN trigger, and if it does (and
> then burns the kernel) we at least know wtf happend.

I certainly don't mind personally, as long as we get the warning. Now
I've seen different
 opinions on matters such as this. Some prefer to have the
auto-correction, some don't.

I'll try as you say and see if anybody gets angry :)

  reply	other threads:[~2017-11-03 14:27 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-10-20  0:55 [PATCH 00/14] lockdep: Add lightweight IRQs disabled/enabled check Frederic Weisbecker
2017-10-20  0:55 ` [PATCH 01/14] lockdep: Add IRQs disabled/enabled assertion Frederic Weisbecker
2017-10-20  0:55 ` [PATCH 02/14] irq: Use lockdep to assert IRQs are disabled/enabled Frederic Weisbecker
2017-10-20  0:56 ` [PATCH 03/14] workqueue: " Frederic Weisbecker
2017-10-21 15:39   ` Tejun Heo
2017-10-20  0:56 ` [PATCH 04/14] nohz: " Frederic Weisbecker
2017-10-20  0:56 ` [PATCH 05/14] hrtimer: " Frederic Weisbecker
2017-10-20  0:56 ` [PATCH 06/14] smp: " Frederic Weisbecker
2017-10-20  0:56 ` [PATCH 07/14] x86: " Frederic Weisbecker
2017-10-22  9:20   ` Peter Zijlstra
2017-11-03 14:25     ` Frederic Weisbecker [this message]
2017-10-20  0:56 ` [PATCH 08/14] perf: " Frederic Weisbecker
2017-10-20  0:56 ` [PATCH 09/14] irq/timings: " Frederic Weisbecker
2017-10-20  0:56 ` [PATCH 10/14] irq_work: " Frederic Weisbecker
2017-10-20  0:56 ` [PATCH 11/14] sched: " Frederic Weisbecker
2017-10-20  0:56 ` [PATCH 12/14] posix-cpu-timers: " Frederic Weisbecker
2017-10-20  0:56 ` [PATCH 13/14] netpoll: " Frederic Weisbecker
2017-10-20  0:56 ` [PATCH 14/14] rcu: " Frederic Weisbecker
2017-10-21 21:36   ` Paul E. McKenney
2017-11-06 15:01 [GIT PULL] lockdep: Add lightweight IRQs disabled/enabled check v2 Frederic Weisbecker
2017-11-06 15:01 ` [PATCH 07/14] x86: Use lockdep to assert IRQs are disabled/enabled Frederic Weisbecker

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