Added a bionic systrace class and tracing to pthread_mutex.cpp.

bionic_systrace.h contains an implementation of tracing that
can be used with systrace.py and its associated viewer.  pthread_mutex
now uses this tracing to track pthread_mutex contention, which can be
enabled by using the "bionic" command line option to systrace.

Bug: 15116468
Change-Id: I30ed5b377c91ca4c36568a0e647ddf95d4e4a61a

1 files changed, 12 insertions, 0 deletions

diff --git a/libc/bionic/pthread_mutex.cpp b/libc/bionic/pthread_mutex.cpp
index 546166166..e00ffb437 100644
--- a/libc/bionic/pthread_mutex.cpp
+++ b/libc/bionic/pthread_mutex.cpp
@@ -39,6 +39,8 @@
 #include "private/bionic_futex.h"
 #include "private/bionic_tls.h"
 
+#include "private/bionic_systrace.h"
+
 extern void pthread_debug_mutex_lock_check(pthread_mutex_t *mutex);
 extern void pthread_debug_mutex_unlock_check(pthread_mutex_t *mutex);
 
@@ -333,6 +335,10 @@ static inline void _normal_lock(pthread_mutex_t* mutex, int shared) {
          * that the mutex is in state 2 when we go to sleep on it, which
          * guarantees a wake-up call.
          */
+
+         ScopedTrace trace("Contending for pthread mutex");
+
+
         while (__bionic_swap(locked_contended, &mutex->value) != unlocked) {
             __futex_wait_ex(&mutex->value, shared, locked_contended, NULL);
         }
@@ -473,6 +479,8 @@ int pthread_mutex_lock(pthread_mutex_t* mutex) {
         mvalue = mutex->value;
     }
 
+    ScopedTrace trace("Contending for pthread mutex");
+
     for (;;) {
         int newval;
 
@@ -626,6 +634,8 @@ static int __pthread_mutex_timedlock(pthread_mutex_t* mutex, const timespec* abs
       return 0;
     }
 
+    ScopedTrace trace("Contending for timed pthread mutex");
+
     // Loop while needed.
     while (__bionic_swap(locked_contended, &mutex->value) != unlocked) {
       if (__timespec_from_absolute(&ts, abs_timeout, clock) < 0) {
@@ -658,6 +668,8 @@ static int __pthread_mutex_timedlock(pthread_mutex_t* mutex, const timespec* abs
     mvalue = mutex->value;
   }
 
+  ScopedTrace trace("Contending for timed pthread mutex");
+
   while (true) {
     // If the value is 'unlocked', try to acquire it directly.
     // NOTE: put state to 2 since we know there is contention.