Added FORCE_MONOTONIC_FIX CFLAG to avoid hangs on timedwait (#202 #142)

5 files changed, 21 insertions, 3 deletions

diff --git a/NEWS b/NEWS
index 26a68a9..cba2534 100644
--- a/NEWS
+++ b/NEWS
@@ -19,6 +19,9 @@ Since 0.9.7:
     - Updated glibc compatibility settings for various platforms
     - Support for clock_nanosleep() with realtime and monotonic clocks
     - Support for epoll_wait(), epoll_pwait(), and pselect()
+    - src/Makefile CFLAG FORCE_MONOTONIC_FIX should be set (only) on
+      platforms where the test program hangs forever at the
+      CLOCK_MONOTONIC test.
 
 Since 0.9.6:
     - Julien Gilli added an option to disable monotonic time faking
diff --git a/README b/README
index fd0f805..892484d 100644
--- a/README
+++ b/README
@@ -83,6 +83,12 @@ documentation whether it can be achieved by using libfaketime directly.
   e.g., by checking whether certain environment variables are set or whether
   libfaketime-specific files are present.
 
+* CLOCK_MONOTONIC test: Running "make test" performs a series of tests after
+  successful compilation of the libfaketime library. On some platforms, the
+  "CLOCK_MONOTONIC test" will apparently hang forever. If and only if this
+  happens on your platform, add the CFLAG -DFORCE_MONOTONIC_FIX to
+  src/Makefile and recompile libfaketime. Do not set FORCE_MONOTONIC_FIX on
+  platforms where the test does not hang.
 
 3. Installation
 ---------------
diff --git a/src/Makefile b/src/Makefile
index e2f047a..07128c3 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -30,6 +30,13 @@
 #     FAKE_PTHREAD
 #         - Intercept pthread_cond_timedwait
 #
+#     FORCE_MONOTONIC_FIX
+#         - If the test program hangs forever on
+#                  " pthread_cond_timedwait: CLOCK_MONOTONIC test
+#                    (Intentionally sleeping 1 second...)          "
+#           then add -DFORCE_MONOTONIC_FIX to CFLAGS and recompile.
+#           (This is a platform-specific issue we cannot handle at run-time.)
+#
 #     MULTI_ARCH
 #  	  - If MULTI_ARCH is set, the faketime wrapper program will put a literal
 #           $LIB into the LD_PRELOAD environment variable it creates, which makes
@@ -50,8 +57,8 @@
 # Change PREFIX to where you want libfaketime (libraries and wrapper binary) installed.
 # LIBDIRNAME is relative to PREFIX. The default is to install into $PREFIX/lib/faketime,
 # but you can set LIBDIRNAME to, e.g., /lib64 if you want to install it elsewhere.
-# LIBDIRNAME has been introduced to support MultiLib systems. Please do not change the 
-# default value on MultiArch systems. 
+# LIBDIRNAME has been introduced to support MultiLib systems. Please do not change the
+# default value on MultiArch systems.
 #
 # For testing in the current directory without installation, try make PREFIX= LIBDIRNAME='.'
 
diff --git a/src/libfaketime.c b/src/libfaketime.c
index 162df4f..9591ea1 100644
--- a/src/libfaketime.c
+++ b/src/libfaketime.c
@@ -3124,10 +3124,12 @@ int pthread_cond_timedwait_common(pthread_cond_t *cond, pthread_mutex_t *mutex,
        fake time needs to be passed to pthread_cond_timedwait for
        CLOCK_MONOTONIC. */
 #ifndef __ARM_ARCH
+#ifndef FORCE_MONOTONIC_FIX
     if(clk_id == CLOCK_MONOTONIC)
       timespecadd(&faketime, &tdiff_actual, &tp);
     else
 #endif
+#endif
       timespecadd(&realtime, &tdiff_actual, &tp);
 
     tf = &tp;
diff --git a/test/timetest.c b/test/timetest.c
index 285d0cc..e9aa837 100644
--- a/test/timetest.c
+++ b/test/timetest.c
@@ -97,7 +97,7 @@ void* pthread_test(void* args)
   timeToWait.tv_nsec = now.tv_nsec;
 
   printf("pthread_cond_timedwait: CLOCK_MONOTONIC test\n");
-  printf("(Intentionally sleeping 1 second...)\n");
+  printf("(Intentionally sleeping 1 second..., see docs about CLOCK_MONOTONIC test)\n");
   fflush(stdout);
 
   pthread_mutex_lock(&fakeMutex);