linux-kernel - Re: [GIT RFC PULL rcu/urgent] Fix noinstr warnings for KCSAN

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Message-ID: <20200626143117.GA1532@paulmck-ThinkPad-P72>
Date:   Fri, 26 Jun 2020 07:31:17 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     mingo@...nel.org, tglx@...utronix.de
Cc:     peterz@...radead.org, x86@...nel.org, elver@...gle.com,
        linux-kernel@...r.kernel.org, rcu@...r.kernel.org
Subject: Re: [GIT RFC PULL rcu/urgent] Fix noinstr warnings for KCSAN

On Thu, Jun 25, 2020 at 09:12:32PM -0700, Paul E. McKenney wrote:
> Hello!
> 
> This pull request contains a single commit that uses "arch_" atomic
> operations to avoid the instrumentation that comes with the non-"arch_"
> versions.  In preparation for that commit, it also has another commit
> that makes these "arch_" atomic operations available to generic code.
> 
> Without these commits, KCSAN uses can see pointless errors.
> 
> This pull request is currently RFC pending ongoing -next testing.

And it has now cleared a round of -next testing!  ;-)

						Thanx, Paul

> This was not entirely free of drama, with Stephen needing to handle
> a merge conflict:
> 
> https://lore.kernel.org/lkml/20200626131425.73ee4e27@canb.auug.org.au/
> 
> However, the resolution looks straightforward to me.  In addition,
> these two commits pass rcutorture testing and associated KCSAN testing.
> 
> The following changes since commit b3a9e3b9622ae10064826dccb4f7a52bd88c7407:
> 
>   Linux 5.8-rc1 (2020-06-14 12:45:04 -0700)
> 
> are available in the git repository at:
> 
>   git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git rcu/urgent
> 
> for you to fetch changes up to b58e733fd774f3f4b49d9e7640d172a57e35200e:
> 
>   rcu: Fixup noinstr warnings (2020-06-25 08:24:32 -0700)
> 
> ----------------------------------------------------------------
> Peter Zijlstra (2):
>       locking/atomics: Provide the arch_atomic_ interface to generic code
>       rcu: Fixup noinstr warnings
> 
>  include/linux/atomic-fallback.h       | 236 +++++++++++++++++++++++++++++++++-
>  include/linux/compiler.h              |   2 +-
>  kernel/rcu/tree.c                     |  32 ++++-
>  scripts/atomic/gen-atomic-fallback.sh |  31 +++++
>  4 files changed, 292 insertions(+), 9 deletions(-)