5 files changed, 65 insertions, 30 deletions

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 2e6d95f97419..9e7012689a84 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -471,8 +471,8 @@ struct hw_perf_event {
                         unsigned long   event_base;
                         int             idx;
                 };
-                union { /* software */
-                        atomic64_t      count;
+                struct { /* software */
+                        s64             remaining;
                         struct hrtimer  hrtimer;
                 };
         };
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index afb7ef3dbc44..7f29643c8985 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -3959,8 +3959,9 @@ static enum hrtimer_restart perf_swevent_hrtimer(struct hrtimer *hrtimer)
                 regs = task_pt_regs(current);
 
         if (regs) {
-                if (perf_event_overflow(event, 0, &data, regs))
-                        ret = HRTIMER_NORESTART;
+                if (!(event->attr.exclude_idle && current->pid == 0))
+                        if (perf_event_overflow(event, 0, &data, regs))
+                                ret = HRTIMER_NORESTART;
         }
 
         period = max_t(u64, 10000, event->hw.sample_period);
@@ -3969,6 +3970,42 @@ static enum hrtimer_restart perf_swevent_hrtimer(struct hrtimer *hrtimer)
         return ret;
 }
 
+static void perf_swevent_start_hrtimer(struct perf_event *event)
+{
+        struct hw_perf_event *hwc = &event->hw;
+
+        hrtimer_init(&hwc->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+        hwc->hrtimer.function = perf_swevent_hrtimer;
+        if (hwc->sample_period) {
+                u64 period;
+
+                if (hwc->remaining) {
+                        if (hwc->remaining < 0)
+                                period = 10000;
+                        else
+                                period = hwc->remaining;
+                        hwc->remaining = 0;
+                } else {
+                        period = max_t(u64, 10000, hwc->sample_period);
+                }
+                __hrtimer_start_range_ns(&hwc->hrtimer,
+                                ns_to_ktime(period), 0,
+                                HRTIMER_MODE_REL, 0);
+        }
+}
+
+static void perf_swevent_cancel_hrtimer(struct perf_event *event)
+{
+        struct hw_perf_event *hwc = &event->hw;
+
+        if (hwc->sample_period) {
+                ktime_t remaining = hrtimer_get_remaining(&hwc->hrtimer);
+                hwc->remaining = ktime_to_ns(remaining);
+
+                hrtimer_cancel(&hwc->hrtimer);
+        }
+}
+
 /*
  * Software event: cpu wall time clock
  */
@@ -3991,22 +4028,14 @@ static int cpu_clock_perf_event_enable(struct perf_event *event)
         int cpu = raw_smp_processor_id();
 
         atomic64_set(&hwc->prev_count, cpu_clock(cpu));
-        hrtimer_init(&hwc->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
-        hwc->hrtimer.function = perf_swevent_hrtimer;
-        if (hwc->sample_period) {
-                u64 period = max_t(u64, 10000, hwc->sample_period);
-                __hrtimer_start_range_ns(&hwc->hrtimer,
-                                ns_to_ktime(period), 0,
-                                HRTIMER_MODE_REL, 0);
-        }
+        perf_swevent_start_hrtimer(event);
 
         return 0;
 }
 
 static void cpu_clock_perf_event_disable(struct perf_event *event)
 {
-        if (event->hw.sample_period)
-                hrtimer_cancel(&event->hw.hrtimer);
+        perf_swevent_cancel_hrtimer(event);
         cpu_clock_perf_event_update(event);
 }
 
@@ -4043,22 +4072,15 @@ static int task_clock_perf_event_enable(struct perf_event *event)
         now = event->ctx->time;
 
         atomic64_set(&hwc->prev_count, now);
-        hrtimer_init(&hwc->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
-        hwc->hrtimer.function = perf_swevent_hrtimer;
-        if (hwc->sample_period) {
-                u64 period = max_t(u64, 10000, hwc->sample_period);
-                __hrtimer_start_range_ns(&hwc->hrtimer,
-                                ns_to_ktime(period), 0,
-                                HRTIMER_MODE_REL, 0);
-        }
+
+        perf_swevent_start_hrtimer(event);
 
         return 0;
 }
 
 static void task_clock_perf_event_disable(struct perf_event *event)
 {
-        if (event->hw.sample_period)
-                hrtimer_cancel(&event->hw.hrtimer);
+        perf_swevent_cancel_hrtimer(event);
         task_clock_perf_event_update(event, event->ctx->time);
 
 }
diff --git a/tools/perf/Makefile b/tools/perf/Makefile
index 742a32eee8fc..7e190d522cd5 100644
--- a/tools/perf/Makefile
+++ b/tools/perf/Makefile
@@ -177,8 +177,7 @@ endif
 # Include saner warnings here, which can catch bugs:
 #
 
-EXTRA_WARNINGS := -Wcast-align
-EXTRA_WARNINGS := $(EXTRA_WARNINGS) -Wformat
+EXTRA_WARNINGS := -Wformat
 EXTRA_WARNINGS := $(EXTRA_WARNINGS) -Wformat-security
 EXTRA_WARNINGS := $(EXTRA_WARNINGS) -Wformat-y2k
 EXTRA_WARNINGS := $(EXTRA_WARNINGS) -Wshadow
@@ -422,7 +421,11 @@ ifeq ($(uname_S),Darwin)
         PTHREAD_LIBS =
 endif
 
-ifneq ($(shell sh -c "(echo '\#include <libelf.h>'; echo 'int main(void) { Elf * elf = elf_begin(0, ELF_C_READ_MMAP, 0); return (long)elf; }') | $(CC) -x c - $(ALL_CFLAGS) -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -o /dev/null $(ALL_LDFLAGS) > /dev/null 2>&1 && echo y"), y)
+ifeq ($(shell sh -c "(echo '\#include <libelf.h>'; echo 'int main(void) { Elf * elf = elf_begin(0, ELF_C_READ, 0); return (long)elf; }') | $(CC) -x c - $(ALL_CFLAGS) -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -o /dev/null $(ALL_LDFLAGS) > /dev/null 2>&1 && echo y"), y)
+        ifneq ($(shell sh -c "(echo '\#include <libelf.h>'; echo 'int main(void) { Elf * elf = elf_begin(0, ELF_C_READ_MMAP, 0); return (long)elf; }') | $(CC) -x c - $(ALL_CFLAGS) -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -o /dev/null $(ALL_LDFLAGS) > /dev/null 2>&1 && echo y"), y)
+                BASIC_CFLAGS += -DLIBELF_NO_MMAP
+        endif
+else
         msg := $(error No libelf.h/libelf found, please install libelf-dev/elfutils-libelf-devel and glibc-dev[el]);
 endif
 
diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 47ea0609a760..226f44a2357d 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -413,7 +413,7 @@ static int dso__synthesize_plt_symbols(struct  dso *self, int v)
         if (fd < 0)
                 goto out;
 
-        elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);
+        elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
         if (elf == NULL)
                 goto out_close;
 
@@ -533,7 +533,7 @@ static int dso__load_sym(struct dso *self, int fd, const char *name,
         Elf *elf;
         int nr = 0, kernel = !strcmp("[kernel]", self->name);
 
-        elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);
+        elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
         if (elf == NULL) {
                 if (v)
                         fprintf(stderr, "%s: cannot read %s ELF file.\n",
@@ -675,7 +675,7 @@ static char *dso__read_build_id(struct dso *self, int v)
         if (fd < 0)
                 goto out;
 
-        elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);
+        elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
         if (elf == NULL) {
                 if (v)
                         fprintf(stderr, "%s: cannot read %s ELF file.\n",
diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
index 6e8490716408..829da9edba64 100644
--- a/tools/perf/util/symbol.h
+++ b/tools/perf/util/symbol.h
@@ -27,6 +27,16 @@ static inline char *bfd_demangle(void __used *v, const char __used *c,
 #endif
 #endif
 
+/*
+ * libelf 0.8.x and earlier do not support ELF_C_READ_MMAP;
+ * for newer versions we can use mmap to reduce memory usage:
+ */
+#ifdef LIBELF_NO_MMAP
+# define PERF_ELF_C_READ_MMAP ELF_C_READ
+#else
+# define PERF_ELF_C_READ_MMAP ELF_C_READ_MMAP
+#endif
+
 #ifndef DMGL_PARAMS
 #define DMGL_PARAMS      (1 << 0)       /* Include function args */
 #define DMGL_ANSI        (1 << 1)       /* Include const, volatile, etc */