From mboxrd@z Thu Jan 1 00:00:00 1970 From: mark.rutland@arm.com (Mark Rutland) Date: Wed, 6 Jan 2016 12:47:53 +0000 Subject: [PATCH 2/2] arm64: factor work_pending state machine to C In-Reply-To: <20160106123011.GN6301@e104818-lin.cambridge.arm.com> References: <20160105172106.GA7088@leverpostej> <1452015215-29506-2-git-send-email-mark.rutland@arm.com> <20160106123011.GN6301@e104818-lin.cambridge.arm.com> Message-ID: <20160106124753.GI563@leverpostej> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, Jan 06, 2016 at 12:30:11PM +0000, Catalin Marinas wrote: > On Tue, Jan 05, 2016 at 05:33:35PM +0000, Mark Rutland wrote: > > Currently ret_fast_syscall, work_pending, and ret_to_user form an ad-hoc > > state machine that can be difficult to reason about due to duplicated > > code and a large number of branch targets. > > > > This patch factors the common logic out into the existing > > do_notify_resume function, converting the code to C in the process, > > making the code more legible. > > > > This patch tries to mirror the existing behaviour as closely as possible > > while using the usual C control flow primitives. There should be no > > functional change as a result of this patch. > > > > Signed-off-by: Mark Rutland > > Cc: Catalin Marinas > > Cc: Chris Metcalf > > Cc: Will Deacon > > This is definitely cleaner. The only downside is slightly more expensive > ret_fast_syscall. I guess it's not noticeable (though we could do some > quick benchmark like getpid in a loop). Anyway, I'm fine with the patch: > > Acked-by: Catalin Marinas Cheers! While any additional overhead hasn't been noticeable, I'll try to get some numbers out as part of the larger deasm testing/benchmarking. Thanks, Mark.