Re: [PATCH] firmware: dmi_scan: Drop dmi_initialized

From	Peter Zijlstra <peterz@infradead.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH] firmware: dmi_scan: Drop dmi_initialized
Date	2017-09-25 11:30 +0200
Message-ID	<utxSa-4rR-11@gated-at.bofh.it> (permalink)
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On Mon, Sep 25, 2017 at 11:00:11AM +0200, Jean Delvare wrote:
> I can find 169 occurrences of "(must|has to|should) be called
> (before|after)" in the kernel source tree, plus 19 occurrences of "call
> this function (before|after)" so apparently I'm not the only fool who
> thinks documenting such ordering requirements is worthwhile.

Documenting things is good, assuming people read it is another. In fact
its provably incorrect, people simply don't read.

I've been slowly converting all those occurrences of "should be called
with 'foo' lock held" into:

	lockdep_assert_held(&foo);

simply because people do _not_ read. And even if they did read, its
still easy to forget and make a mistake.

Heck, I sometimes get it wrong on code I wrote.

Documentation good, runtime checks also good.

Because when you do get it wrong p(someone getting it wrong at some
point) = 1, a WARN_ON_ONCE() triggering that has a comment that says:

 /*
  * if you trigger this; you violated rule #123
  */
 WARN_ON_ONCE(!invariant_cond_123);

saves ever so much more time than debugging weird and wonderful splats
much later in the code that rely on our rule #123.

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[PATCH] firmware: dmi_scan: Drop dmi_initialized Jean Delvare <jdelvare@suse.de> - 2017-09-18 10:10 +0200
  Re: [PATCH] firmware: dmi_scan: Drop dmi_initialized Ingo Molnar <mingo@kernel.org> - 2017-09-23 13:00 +0200
    Re: [PATCH] firmware: dmi_scan: Drop dmi_initialized Jean Delvare <jdelvare@suse.de> - 2017-09-23 17:30 +0200
      Re: [PATCH] firmware: dmi_scan: Drop dmi_initialized Ingo Molnar <mingo@kernel.org> - 2017-09-24 11:20 +0200
        Re: [PATCH] firmware: dmi_scan: Drop dmi_initialized Jean Delvare <jdelvare@suse.de> - 2017-09-25 11:10 +0200
          Re: [PATCH] firmware: dmi_scan: Drop dmi_initialized Peter Zijlstra <peterz@infradead.org> - 2017-09-25 11:30 +0200
          Re: [PATCH] firmware: dmi_scan: Drop dmi_initialized Peter Zijlstra <peterz@infradead.org> - 2017-09-25 11:30 +0200

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