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Re: [PATCH] atomic: Fix bugs in 'fetch_or()' and rename it to 'xchg_or()'

From Peter Zijlstra <peterz@infradead.org>
Newsgroups linux.kernel
Subject Re: [PATCH] atomic: Fix bugs in 'fetch_or()' and rename it to 'xchg_or()'
Date 2016-03-15 13:50 +0100
Message-ID <rcWAa-29w-5@gated-at.bofh.it> (permalink)
References <rczWV-3JY-15@gated-at.bofh.it> <rcNdw-49L-5@gated-at.bofh.it> <rcTCk-bX-35@gated-at.bofh.it> <rcURH-Us-1@gated-at.bofh.it> <rcVXs-1TR-5@gated-at.bofh.it>
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On Tue, Mar 15, 2016 at 01:08:35PM +0100, Ingo Molnar wrote:
> * Peter Zijlstra <peterz@infradead.org> wrote:
> 
> > On Tue, Mar 15, 2016 at 10:32:45AM +0100, Ingo Molnar wrote:
> > >  2) its naming sucks. "fetch_or()" does not really signal that it's a
> > >     fundamentally atomic operation, nor what API family it belongs to.
> > 
> > I disagree there, the fetch-$op naming is widely used for atomic
> > operations that return the previous value. See for example the C/C++11
> > atomic ops.
> 
> The problem I see is that we don't really have the fetch_*() naming in the kernel 
> right now, while we do have the xchg_*() naming. The latter is 'obviously' an 
> atomic operation - while 'fetch' could be anything.

We don't have xchg_*() naming, we have xchg() and that's about it. And
yes, people know xchg() is an atomic op. But 'fetch (and) or' is also
atomic, it has to be, it needs to do 2 operations in 1.

Furthermore, the relevant wikipedia page is:

  https://en.wikipedia.org/wiki/Fetch-and-add

So the naming is widely established.

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Thread

[GIT PULL] NOHZ updates for v4.6 Ingo Molnar <mingo@kernel.org> - 2016-03-14 13:40 +0100
  Re: [GIT PULL] NOHZ updates for v4.6 Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-15 03:50 +0100
    Re: [GIT PULL] NOHZ updates for v4.6 Peter Zijlstra <peterz@infradead.org> - 2016-03-15 09:50 +0100
      Re: [GIT PULL] NOHZ updates for v4.6 Ingo Molnar <mingo@kernel.org> - 2016-03-15 10:50 +0100
    [PATCH] atomic: Fix bugs in 'fetch_or()' and rename it to 'xchg_or()' Ingo Molnar <mingo@kernel.org> - 2016-03-15 10:40 +0100
      Re: [PATCH] atomic: Fix bugs in 'fetch_or()' and rename it to  'xchg_or()' Peter Zijlstra <peterz@infradead.org> - 2016-03-15 12:00 +0100
        Re: [PATCH] atomic: Fix bugs in 'fetch_or()' and rename it to  'xchg_or()' Ingo Molnar <mingo@kernel.org> - 2016-03-15 13:10 +0100
          Re: [PATCH] atomic: Fix bugs in 'fetch_or()' and rename it to  'xchg_or()' Peter Zijlstra <peterz@infradead.org> - 2016-03-15 13:50 +0100
      Re: [PATCH] atomic: Fix bugs in 'fetch_or()' and rename it to  'xchg_or()' Peter Zijlstra <peterz@infradead.org> - 2016-03-15 12:10 +0100
      Re: [PATCH] atomic: Fix bugs in 'fetch_or()' and rename it to  'xchg_or()' Ingo Molnar <mingo@kernel.org> - 2016-03-15 13:10 +0100
        Re: [PATCH] atomic: Fix bugs in 'fetch_or()' and rename it to  'xchg_or()' Ingo Molnar <mingo@kernel.org> - 2016-03-15 13:40 +0100
          Re: [PATCH] atomic: Fix bugs in 'fetch_or()' and rename it to  'xchg_or()' Ingo Molnar <mingo@kernel.org> - 2016-03-15 13:40 +0100
          Re: [PATCH] atomic: Fix bugs in 'fetch_or()' and rename it to  'xchg_or()' Peter Zijlstra <peterz@infradead.org> - 2016-03-15 14:20 +0100
      Re: [PATCH] atomic: Fix bugs in 'fetch_or()' and rename it to  'xchg_or()' Peter Zijlstra <peterz@infradead.org> - 2016-03-15 13:30 +0100
      [PATCH v2] atomic: Fix bugs in 'fetch_or()' and rename it to  'xchg_or()' Ingo Molnar <mingo@kernel.org> - 2016-03-15 13:30 +0100
        Re: [PATCH v2] atomic: Fix bugs in 'fetch_or()' and rename it to  'xchg_or()' Peter Zijlstra <peterz@infradead.org> - 2016-03-15 14:30 +0100
          Re: [PATCH v2] atomic: Fix bugs in 'fetch_or()' and rename it to  'xchg_or()' Ingo Molnar <mingo@kernel.org> - 2016-03-16 09:10 +0100
            Re: [PATCH v2] atomic: Fix bugs in 'fetch_or()' and rename it to  'xchg_or()' Peter Zijlstra <peterz@infradead.org> - 2016-03-16 09:40 +0100
        Re: [PATCH v2] atomic: Fix bugs in 'fetch_or()' and rename it to  'xchg_or()' Frederic Weisbecker <fweisbec@gmail.com> - 2016-03-15 18:10 +0100
          Re: [PATCH v2] atomic: Fix bugs in 'fetch_or()' and rename it to  'xchg_or()' Ingo Molnar <mingo@kernel.org> - 2016-03-16 09:20 +0100
            Re: [PATCH v2] atomic: Fix bugs in 'fetch_or()' and rename it to  'xchg_or()' Frederic Weisbecker <fweisbec@gmail.com> - 2016-03-17 02:00 +0100
      Re: [PATCH] atomic: Fix bugs in 'fetch_or()' and rename it to 'xchg_or()' Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-15 17:20 +0100
    [PATCH] nohz: Change tick_dep_mask from 'unsigned long' to 'unsigned  int' Ingo Molnar <mingo@kernel.org> - 2016-03-15 11:00 +0100
      Re: [PATCH] nohz: Change tick_dep_mask from 'unsigned long' to  'unsigned int' Ingo Molnar <mingo@kernel.org> - 2016-03-15 13:20 +0100
        Re: [PATCH] nohz: Change tick_dep_mask from 'unsigned long' to  'unsigned int' Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-15 17:40 +0100
          Re: [PATCH] nohz: Change tick_dep_mask from 'unsigned long' to  'unsigned int' Frederic Weisbecker <fweisbec@gmail.com> - 2016-03-15 18:30 +0100
            Re: [PATCH] nohz: Change tick_dep_mask from 'unsigned long' to  'unsigned int' Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-15 18:40 +0100

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