linux-kernel - Re: "locking/lockdep: Consolidate lock usage bit initialization" is buggy

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Date:   Fri, 7 Jun 2019 11:21:58 +0800
From:   Yuyang Du <duyuyang@...il.com>
To:     Qian Cai <cai@....pw>
Cc:     "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: "locking/lockdep: Consolidate lock usage bit initialization" is buggy

Thanks for the report, but

On Fri, 7 Jun 2019 at 05:14, Qian Cai <cai@....pw> wrote:
>
> The linux-next commit "locking/lockdep: Consolidate lock usage bit
> initialization" [1] will always generate a warning below.

I never had such warning.

> Looking through the
> commit that when mark_irqflags() returns 1 and check = 1, it will do one less
> mark_lock() call than it used to.

The four cases:

1. When check == 1 and mark_irqflags() returns 1;
2. When check == 1 and mark_irqflags() returns 0;
3. When check == 0 and mark_irqflags() returns 1;
4. When check == 0 and mark_irqflags() returns 0;

Before and after have exactly the same code to do.