From: Peter Zijlstra <peterz@infradead.org>
To: Mark Rutland <mark.rutland@arm.com>
Cc: Andrea Parri <andrea.parri@amarulasolutions.com>,
linux-kernel@vger.kernel.org, will.deacon@arm.com,
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 13:18:07 +0200 [thread overview]
Message-ID: <20190524111807.GS2650@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20190524103731.GN2606@hirez.programming.kicks-ass.net>
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.
+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.
+
The one detail to this is that atomic_set{}() should be observable to the RMW
ops. That is:
next prev parent reply other threads:[~2019-05-24 11:18 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 [this message]
2019-05-24 11:38 ` Greg KH
2019-05-24 11:42 ` Will Deacon
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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