From: Will Deacon <will.deacon@arm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
Andrea Parri <andrea.parri@amarulasolutions.com>,
linux-kernel@vger.kernel.org, aou@eecs.berkeley.edu,
arnd@arndb.de, bp@alien8.de, catalin.marinas@arm.com,
davem@davemloft.net, fenghua.yu@intel.com,
heiko.carstens@de.ibm.com, herbert@gondor.apana.org.au,
ink@jurassic.park.msu.ru, jhogan@kernel.org,
linux@armlinux.org.uk, mattst88@gmail.com, mingo@kernel.org,
mpe@ellerman.id.au, palmer@sifive.com, paul.burton@mips.com,
paulus@samba.org, ralf@linux-mips.org, rth@twiddle.net,
stable@vger.kernel.org, tglx@linutronix.de, tony.luck@intel.com,
vgupta@synopsys.com, gregkh@linuxfoundation.org,
jhansen@vmware.com, vdasa@vmware.com, aditr@vmware.com,
Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH 00/18] locking/atomic: atomic64 type cleanup
Date: Fri, 24 May 2019 12:42:20 +0100 [thread overview]
Message-ID: <20190524114220.GA4260@fuggles.cambridge.arm.com> (raw)
In-Reply-To: <20190524111807.GS2650@hirez.programming.kicks-ass.net>
On Fri, May 24, 2019 at 01:18:07PM +0200, Peter Zijlstra wrote:
> On Fri, May 24, 2019 at 12:37:31PM +0200, Peter Zijlstra wrote:
> > On Thu, May 23, 2019 at 11:19:26AM +0100, Mark Rutland wrote:
> >
> > > [mark@lakrids:~/src/linux]% git grep '\(return\|=\)\s\+atomic\(64\)\?_set'
> > > include/linux/vmw_vmci_defs.h: return atomic_set((atomic_t *)var, (u32)new_val);
> > > include/linux/vmw_vmci_defs.h: return atomic64_set(var, new_val);
> > >
> >
> > Oh boy, what a load of crap you just did find.
> >
> > How about something like the below? I've not read how that buffer is
> > used, but the below preserves all broken without using atomic*_t.
>
> Clarified by something along these lines?
>
> ---
> Documentation/atomic_t.txt | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/Documentation/atomic_t.txt b/Documentation/atomic_t.txt
> index dca3fb0554db..125c95ddbbc0 100644
> --- a/Documentation/atomic_t.txt
> +++ b/Documentation/atomic_t.txt
> @@ -83,6 +83,9 @@ The non-RMW ops are (typically) regular LOADs and STOREs and are canonically
> implemented using READ_ONCE(), WRITE_ONCE(), smp_load_acquire() and
> smp_store_release() respectively.
>
Not sure you need a new paragraph here.
> +Therefore, if you find yourself only using the Non-RMW operations of atomic_t,
> +you do not in fact need atomic_t at all and are doing it wrong.
> +
That makes sense to me, although I now find that the sentence below is a bit
confusing because it sounds like it's a caveat relating to only using
Non-RMW ops.
> The one detail to this is that atomic_set{}() should be observable to the RMW
> ops. That is:
How about changing this to be:
"A subtle detail of atomic_set{}() is that it should be observable..."
With that:
Acked-by: Will Deacon <will.deacon@arm.com>
Will
next prev parent reply other threads:[~2019-05-24 11:42 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-22 13:22 [PATCH 00/18] locking/atomic: atomic64 type cleanup Mark Rutland
2019-05-22 13:22 ` [PATCH 01/18] locking/atomic: crypto: nx: prepare for atomic64_read() conversion Mark Rutland
2019-05-22 13:22 ` [PATCH 02/18] locking/atomic: s390/pci: " Mark Rutland
2019-05-22 13:22 ` [PATCH 03/18] locking/atomic: generic: use s64 for atomic64 Mark Rutland
2019-05-22 21:16 ` Arnd Bergmann
2019-05-22 13:22 ` [PATCH 04/18] locking/atomic: alpha: " Mark Rutland
2019-05-22 13:22 ` [PATCH 05/18] locking/atomic: arc: " Mark Rutland
2019-05-23 23:10 ` Vineet Gupta
2019-05-22 13:22 ` [PATCH 06/18] locking/atomic: arm: " Mark Rutland
2019-05-22 13:22 ` [PATCH 07/18] locking/atomic: arm64: " Mark Rutland
2019-05-22 13:22 ` [PATCH 08/18] locking/atomic: ia64: " Mark Rutland
2019-05-22 13:22 ` [PATCH 09/18] locking/atomic: mips: " Mark Rutland
2019-05-22 13:22 ` [PATCH 10/18] locking/atomic: powerpc: " Mark Rutland
2019-05-23 13:27 ` Michael Ellerman
2019-05-22 13:22 ` [PATCH 11/18] locking/atomic: riscv: fix atomic64_sub_if_positive() offset argument Mark Rutland
2019-05-22 19:06 ` Palmer Dabbelt
2019-05-22 13:22 ` [PATCH 12/18] locking/atomic: riscv: use s64 for atomic64 Mark Rutland
2019-05-22 19:06 ` Palmer Dabbelt
2019-05-23 10:23 ` Mark Rutland
2019-05-22 13:22 ` [PATCH 13/18] locking/atomic: s390: " Mark Rutland
2019-05-22 13:22 ` [PATCH 14/18] locking/atomic: sparc: " Mark Rutland
2019-05-22 13:22 ` [PATCH 15/18] locking/atomic: x86: " Mark Rutland
2019-05-22 13:22 ` [PATCH 16/18] locking/atomic: use s64 for atomic64_t on 64-bit Mark Rutland
2019-05-22 13:22 ` [PATCH 17/18] locking/atomic: crypto: nx: remove redundant casts Mark Rutland
2019-05-22 13:22 ` [PATCH 18/18] locking/atomic: s390/pci: " Mark Rutland
2019-05-22 21:18 ` [PATCH 00/18] locking/atomic: atomic64 type cleanup Arnd Bergmann
2019-05-23 10:28 ` Mark Rutland
2019-05-23 8:30 ` Andrea Parri
2019-05-23 10:19 ` Mark Rutland
2019-05-23 11:20 ` Andrea Parri
2019-05-24 10:37 ` Peter Zijlstra
2019-05-24 11:18 ` Peter Zijlstra
2019-05-24 11:38 ` Greg KH
2019-05-24 11:42 ` Will Deacon [this message]
2019-05-24 11:52 ` Peter Zijlstra
2019-05-24 22:43 ` Andrea Parri
2019-05-28 10:47 ` Peter Zijlstra
2019-05-28 11:15 ` Andrea Parri
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