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authorDaniel Thompson <daniel.thompson@linaro.org>2015-03-26 12:23:26 -0700
committerIngo Molnar <mingo@kernel.org>2015-03-27 08:34:00 +0100
commit1809bfa44e1019e397fabaa6f2349bb7237e57a4 (patch)
tree3d2eba58ee4389f00e87b752599c9703f34b7150 /arch/tile
parent9fee69a8c8070b38b558161a3f18bd5e2b664682 (diff)
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timers, sched/clock: Avoid deadlock during read from NMI
Currently it is possible for an NMI (or FIQ on ARM) to come in and read sched_clock() whilst update_sched_clock() has locked the seqcount for writing. This results in the NMI handler locking up when it calls raw_read_seqcount_begin(). This patch fixes the NMI safety issues by providing banked clock data. This is a similar approach to the one used in Thomas Gleixner's 4396e058c52e("timekeeping: Provide fast and NMI safe access to CLOCK_MONOTONIC"). Suggested-by: Stephen Boyd <sboyd@codeaurora.org> Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org> Signed-off-by: John Stultz <john.stultz@linaro.org> Reviewed-by: Stephen Boyd <sboyd@codeaurora.org> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Russell King <linux@arm.linux.org.uk> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Will Deacon <will.deacon@arm.com> Link: http://lkml.kernel.org/r/1427397806-20889-6-git-send-email-john.stultz@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
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