From 4aaca90c0255caee9a55371afaecb32365123762 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Mon, 19 Aug 2013 17:33:26 -0400 Subject: [PATCH 2/3] hwlat-detector: Use trace_clock_local if available Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/3.10/patches-3.10.10-rt7.tar.xz As ktime_get() calls into the timing code which does a read_seq(), it may be affected by other CPUS that touch that lock. To remove this dependency, use the trace_clock_local() which is already exported for module use. If CONFIG_TRACING is enabled, use that as the clock, otherwise use ktime_get(). Signed-off-by: Steven Rostedt Signed-off-by: Sebastian Andrzej Siewior --- drivers/misc/hwlat_detector.c | 34 +++++++++++++++++++++++++--------- 1 file changed, 25 insertions(+), 9 deletions(-) --- a/drivers/misc/hwlat_detector.c +++ b/drivers/misc/hwlat_detector.c @@ -51,6 +51,7 @@ #include #include #include +#include #define BUF_SIZE_DEFAULT 262144UL /* 8K*(sizeof(entry)) */ #define BUF_FLAGS (RB_FL_OVERWRITE) /* no block on full */ @@ -211,6 +212,21 @@ static struct sample *buffer_get_sample( return sample; } +#ifndef CONFIG_TRACING +#define time_type ktime_t +#define time_get() ktime_get() +#define time_to_us(x) ktime_to_us(x) +#define time_sub(a, b) ktime_sub(a, b) +#define init_time(a, b) (a).tv64 = b +#define time_u64(a) (a).tv64 +#else +#define time_type u64 +#define time_get() trace_clock_local() +#define time_to_us(x) div_u64(x, 1000) +#define time_sub(a, b) ((a) - (b)) +#define init_time(a, b) a = b +#define time_u64(a) a +#endif /** * get_sample - sample the CPU TSC and look for likely hardware latencies * @unused: This is not used but is a part of the stop_machine API @@ -220,23 +236,23 @@ static struct sample *buffer_get_sample( */ static int get_sample(void *unused) { - ktime_t start, t1, t2, last_t2; + time_type start, t1, t2, last_t2; s64 diff, total = 0; u64 sample = 0; u64 outer_sample = 0; int ret = 1; - last_t2.tv64 = 0; - start = ktime_get(); /* start timestamp */ + init_time(last_t2, 0); + start = time_get(); /* start timestamp */ do { - t1 = ktime_get(); /* we'll look for a discontinuity */ - t2 = ktime_get(); + t1 = time_get(); /* we'll look for a discontinuity */ + t2 = time_get(); - if (last_t2.tv64) { + if (time_u64(last_t2)) { /* Check the delta from the outer loop (t2 to next t1) */ - diff = ktime_to_us(ktime_sub(t1, last_t2)); + diff = time_to_us(time_sub(t1, last_t2)); /* This shouldn't happen */ if (diff < 0) { printk(KERN_ERR BANNER "time running backwards\n"); @@ -247,10 +263,10 @@ static int get_sample(void *unused) } last_t2 = t2; - total = ktime_to_us(ktime_sub(t2, start)); /* sample width */ + total = time_to_us(time_sub(t2, start)); /* sample width */ /* This checks the inner loop (t1 to t2) */ - diff = ktime_to_us(ktime_sub(t2, t1)); /* current diff */ + diff = time_to_us(time_sub(t2, t1)); /* current diff */ /* This shouldn't happen */ if (diff < 0) {