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Message-ID: <20210622144546.GB71782@C02TD0UTHF1T.local>
Date: Tue, 22 Jun 2021 15:45:46 +0100
From: Mark Rutland <mark.rutland@....com>
To: Will Deacon <will@...nel.org>
Cc: linux-kernel@...r.kernel.org, boqun.feng@...il.com, bp@...en8.de,
catalin.marinas@....com, dvyukov@...gle.com, elver@...gle.com,
ink@...assic.park.msu.ru, jonas@...thpole.se,
juri.lelli@...hat.com, linux@...linux.org.uk, luto@...nel.org,
mattst88@...il.com, mingo@...hat.com, monstr@...str.eu,
paulmck@...nel.org, peterz@...radead.org, rth@...ddle.net,
shorne@...il.com, stefan.kristiansson@...nalahti.fi,
tglx@...utronix.de, vincent.guittot@...aro.org
Subject: Re: [PATCH v2 0/9] thread_info: use helpers to snapshot thread flags
On Mon, Jun 21, 2021 at 06:54:53PM +0100, Will Deacon wrote:
> On Mon, Jun 21, 2021 at 10:05:52AM +0100, Mark Rutland wrote:
> > As thread_info::flags scan be manipulated by remote threads, it is
> > necessary to use atomics or READ_ONCE() to ensure that code manipulates
> > a consistent snapshot, but we open-code plain accesses to
> > thread_info::flags across the kernel tree.
> >
> > Generally we get away with this, but tools like KCSAN legitimately warn
> > that there is a data-race, and this is potentially fragile with compiler
> > optimizations, LTO, etc.
> >
> > These patches introduce new helpers to snahpshot the thread flags, with
> > the intent being that these should replace all plain accesses.
> >
> > Since v1 [1]:
> > * Drop RFC
> > * Make read_ti_thread_flags() __always_inline
> > * Clarify commit messages
> > * Fix typo in arm64 patch
> > * Accumulate Reviewed-by / Acked-by tags
> > * Drop powerpc patch to avoid potential conflicts (per [2])
> >
> > [1] https://lore.kernel.org/r/20210609122001.18277-1-mark.rutland@arm.com
> > [2] https://lore.kernel.org/r/87k0mvtgeb.fsf@mpe.ellerman.id.au
> >
> > Thanks,
> > Mark.
> >
> > Mark Rutland (9):
> > thread_info: add helpers to snapshot thread flags
> > entry: snapshot thread flags
> > sched: snapshot thread flags
> > alpha: snapshot thread flags
> > arm: snapshot thread flags
> > arm64: snapshot thread flags
>
> FWIW, you have two identical arm64 patches in this series, just with a
> different subject.
Whoops; I'd tried to bring arm64 in line with the other patches, but
forgot to delete the stale patch file when I did that. I'll keep the
"snapshot thread flags" version.
> For the one you decide to keep:
>
> Acked-by: Will Deacon <will@...nel.org>
Thanks!
Mark.
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