From: Deng-Cheng Zhu Date: Fri, 21 Jan 2011 08:19:21 +0000 (+0800) Subject: MIPS, Perf-events: Use unsigned delta for right shift in event update X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=ba9786f32473410bbec256db9745a7fbcaace69f;p=GitHub%2Fmt8127%2Fandroid_kernel_alcatel_ttab.git MIPS, Perf-events: Use unsigned delta for right shift in event update Leverage the commit for ARM by Will Deacon: - 446a5a8b1eb91a6990e5c8fe29f14e7a95b69132 ARM: 6205/1: perf: ensure counter delta is treated as unsigned Hardware performance counters on ARM are 32-bits wide but atomic64_t variables are used to represent counter data in the hw_perf_event structure. The armpmu_event_update function right-shifts a signed 64-bit delta variable and adds the result to the event count. This can lead to shifting in sign-bits if the MSB of the 32-bit counter value is set. This results in perf output such as: Performance counter stats for 'sleep 20': 18446744073460670464 cycles <-- 0xFFFFFFFFF12A6000 7783773 instructions # 0.000 IPC 465 context-switches 161 page-faults 1172393 branches 20.154242147 seconds time elapsed This patch ensures that the delta value is treated as unsigned so that the right shift sets the upper bits to zero. Acked-by: Will Deacon Acked-by: David Daney Signed-off-by: Deng-Cheng Zhu To: a.p.zijlstra@chello.nl To: fweisbec@gmail.com To: will.deacon@arm.com Cc: linux-mips@linux-mips.org Cc: linux-kernel@vger.kernel.org Cc: wuzhangjin@gmail.com Cc: paulus@samba.org Cc: mingo@elte.hu Cc: acme@redhat.com Cc: matt@console-pimps.org Cc: sshtylyov@mvista.com Patchwork: http://patchwork.linux-mips.org/patch/2015/ Signed-off-by: Ralf Baechle --- diff --git a/arch/mips/kernel/perf_event.c b/arch/mips/kernel/perf_event.c index 8f7d2f84d095..a8244854d3dc 100644 --- a/arch/mips/kernel/perf_event.c +++ b/arch/mips/kernel/perf_event.c @@ -169,7 +169,7 @@ static void mipspmu_event_update(struct perf_event *event, unsigned long flags; int shift = 64 - TOTAL_BITS; s64 prev_raw_count, new_raw_count; - s64 delta; + u64 delta; again: prev_raw_count = local64_read(&hwc->prev_count);