linux-kernel - [PATCH bitmap-for-next 0/5] bitmap,cpumask: Add for_each_cpu

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Message-Id: <20221003153420.285896-1-vschneid@redhat.com>
Date:   Mon,  3 Oct 2022 16:34:15 +0100
From:   Valentin Schneider <vschneid@...hat.com>
To:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Jens Axboe <axboe@...nel.dk>, Yury Norov <yury.norov@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>
Subject: [PATCH bitmap-for-next 0/5] bitmap,cpumask: Add for_each_cpu_andnot()

As suggested by Yury, this is the bitmap/cpumask specific bits of [1]. This now
also contains an extra fix for blk_mq.

This is based on top of Yury's bitmap-for-next [2].

A note on treewide use of for_each_cpu_andnot()
===============================================

I've used the below coccinelle script to find places that could be patched (I
couldn't figure out the valid syntax to patch from coccinelle itself):

,-----
@tmpandnot@
expression tmpmask;
iterator for_each_cpu;
position p;
statement S;
@@
cpumask_andnot(tmpmask, ...);

...

(
for_each_cpu@p(..., tmpmask, ...)
	S
|
for_each_cpu@p(..., tmpmask, ...)
{
	...
}
)

@script:python depends on tmpandnot@
p << tmpandnot.p;
@@
coccilib.report.print_report(p[0], "andnot loop here")
'-----

Which yields (against c40e8341e3b3):

.//arch/powerpc/kernel/smp.c:1587:1-13: andnot loop here
.//arch/powerpc/kernel/smp.c:1530:1-13: andnot loop here
.//arch/powerpc/kernel/smp.c:1440:1-13: andnot loop here
.//arch/powerpc/platforms/powernv/subcore.c:306:2-14: andnot loop here
.//arch/x86/kernel/apic/x2apic_cluster.c:62:1-13: andnot loop here
.//drivers/acpi/acpi_pad.c:110:1-13: andnot loop here
.//drivers/cpufreq/armada-8k-cpufreq.c:148:1-13: andnot loop here
.//drivers/cpufreq/powernv-cpufreq.c:931:1-13: andnot loop here
.//drivers/net/ethernet/sfc/efx_channels.c:73:1-13: andnot loop here
.//drivers/net/ethernet/sfc/siena/efx_channels.c:73:1-13: andnot loop here
.//kernel/sched/core.c:345:1-13: andnot loop here
.//kernel/sched/core.c:366:1-13: andnot loop here
.//net/core/dev.c:3058:1-13: andnot loop here

A lot of those are actually of the shape

  for_each_cpu(cpu, mask) {
      ...
      cpumask_andnot(mask, ...);
  }

I think *some* of the powerpc ones would be a match for for_each_cpu_andnot(),
but I decided to just stick to the one obvious one in __sched_core_flip().

[1]: https://lore.kernel.org/all/20220923132527.1001870-1-vschneid@redhat.com/
[2]: https://github.com/norov/linux.git/ -b bitmap-for-next

Cheers,
Valentin

Valentin Schneider (5):
  blk_mq: Fix cpumask_check() warning in blk_mq_hctx_next_cpu()
  lib/find_bit: Introduce find_next_andnot_bit()
  cpumask: Introduce for_each_cpu_andnot()
  lib/test_cpumask: Add for_each_cpu_and(not) tests
  sched/core: Merge cpumask_andnot()+for_each_cpu() into
    for_each_cpu_andnot()

 block/blk-mq.c          |  9 +++++++--
 include/linux/cpumask.h | 18 ++++++++++++++++++
 include/linux/find.h    | 38 ++++++++++++++++++++++++++++++++++++++
 kernel/sched/core.c     |  5 +----
 lib/cpumask_kunit.c     | 19 +++++++++++++++++++
 lib/find_bit.c          |  9 +++++++++
 6 files changed, 92 insertions(+), 6 deletions(-)

--
2.31.1