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Date: Mon, 29 Feb 2016 11:35:06 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
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Subject: Re: [PATCH v4 1/5] getcpu_cache system call: cache CPU number of
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On Sun, Feb 28, 2016 at 02:32:28PM +0000, Mathieu Desnoyers wrote:
> The part of ABI I'm trying to express here is for discoverability
> of available features by user-space. For instance, a kernel
> could be configured with "CONFIG_RSEQ=n", and userspace should
> not rely on the rseq fields of the thread-local ABI in that case.

Per the just proposed interface; discoverability would end with:

	thread_local_abi_register(NULL, TLA_ENABLE_RSEQ, 0);

failing. This would indicate your kernel does not support (or your glibc
failed to register, depending on error code I suppose).

Then your program can either fall back to full atomics or just bail.