Messages in this thread | | | From | David Laight <> | Subject | RE: [PATCH v2 18/18] arm64: select ARCH_SUPPORTS_LTO_CLANG | Date | Tue, 21 Nov 2017 17:23:52 +0000 |
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From: Paul E. McKenney > Sent: 20 November 2017 20:54 > > On Mon, Nov 20, 2017 at 08:32:56PM +0100, Peter Zijlstra wrote: > > On Mon, Nov 20, 2017 at 06:05:55PM +0000, Will Deacon wrote: > > > Although the current direction of the C++ committee is to prefer > > > that dependencies are explicitly "marked", this is not deemed to be > > > acceptable for the kernel (in other words, everything is always considered > > > "marked"). > > > > Yeah, that is an attitude not compatible with existing code. Much like > > the proposal to allow temporary/wide stores on everything not explicitly > > declared atomic. Such stuff instantly breaks all extant code that does > > multi-threading with no recourse. > > If someone suggests temporary/wide stores, even on non-atomics, tell > them that the standard does not permit them to introduce data races.
The C standard doesn't say anything about multi-threading.
The x86 bis (bit set) family are well known for being problematic because they always do a 32bit wide rmw cycle.
David
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