From 0a487aad2dfd088bcbbe1766944280b40ff969a5 Mon Sep 17 00:00:00 2001 From: Alexander Shishkin Date: Tue, 21 Apr 2015 16:16:17 +0300 Subject: [PATCH] perf/x86/intel/pt: Kill pt_is_running() Initially, we were trying to guard against scenarios where somebody attaches to the system with a hardware debugger while PT is enabled from software and pt_is_running() tries to make sure we handle this better, but the truth is, there is still a race window no matter what and people with hardware debuggers should really know what they are doing anyway. In other words, there is no point in keeping this one around, and it's one RDMSR instructions fewer in the fast path. The case when PT is enabled by the BIOS at boot time is handled in the driver initialization path and doesn't use pt_is_running(). This patch gets rid of it. Signed-off-by: Alexander Shishkin Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Paul Mackerras Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: acme@infradead.org Cc: adrian.hunter@intel.com Cc: hpa@zytor.com Link: http://lkml.kernel.org/r/1429622177-22843-6-git-send-email-alexander.shishkin@linux.intel.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/perf_event_intel_pt.c | 11 +---------- 1 file changed, 1 insertion(+), 10 deletions(-) diff --git a/arch/x86/kernel/cpu/perf_event_intel_pt.c b/arch/x86/kernel/cpu/perf_event_intel_pt.c index 40ba5e4312d4..a2d407172d61 100644 --- a/arch/x86/kernel/cpu/perf_event_intel_pt.c +++ b/arch/x86/kernel/cpu/perf_event_intel_pt.c @@ -187,15 +187,6 @@ static bool pt_event_valid(struct perf_event *event) * These all are cpu affine and operate on a local PT */ -static bool pt_is_running(void) -{ - u64 ctl; - - rdmsrl(MSR_IA32_RTIT_CTL, ctl); - - return !!(ctl & RTIT_CTL_TRACEEN); -} - static void pt_config(struct perf_event *event) { u64 reg; @@ -933,7 +924,7 @@ static void pt_event_start(struct perf_event *event, int mode) struct pt *pt = this_cpu_ptr(&pt_ctx); struct pt_buffer *buf = perf_get_aux(&pt->handle); - if (pt_is_running() || !buf || pt_buffer_is_full(buf, pt)) { + if (!buf || pt_buffer_is_full(buf, pt)) { event->hw.state = PERF_HES_STOPPED; return; } -- 2.20.1