Avoid underflow in alcnd_timedwait if the time point is already passed

1 files changed, 22 insertions, 6 deletions

diff --git a/common/threads.c b/common/threads.c
index 6272dd9f..5a177a2c 100644
--- a/common/threads.c
+++ b/common/threads.c
@@ -264,10 +264,19 @@ int alcnd_timedwait(alcnd_t *cond, almtx_t *mtx, const struct timespec *time_poi
     if(altimespec_get(&curtime, AL_TIME_UTC) != AL_TIME_UTC)
         return althrd_error;
 
-    sleeptime  = (time_point->tv_nsec - curtime.tv_nsec + 999999)/1000000;
-    sleeptime += (time_point->tv_sec - curtime.tv_sec)*1000;
-    if(SleepConditionVariableCS(cond, mtx, sleeptime) != 0)
-        return althrd_success;
+    if(curtime.tv_sec > time_point->tv_sec || (curtime.tv_sec == time_point->tv_sec &&
+                                               curtime.tv_nsec >= time_point->tv_nsec))
+    {
+        if(SleepConditionVariableCS(cond, mtx, 0) != 0)
+            return althrd_success;
+    }
+    else
+    {
+        sleeptime  = (time_point->tv_nsec - curtime.tv_nsec + 999999)/1000000;
+        sleeptime += (time_point->tv_sec - curtime.tv_sec)*1000;
+        if(SleepConditionVariableCS(cond, mtx, sleeptime) != 0)
+            return althrd_success;
+    }
     return (GetLastError()==ERROR_TIMEOUT) ? althrd_timedout : althrd_error;
 }
 
@@ -364,8 +373,15 @@ int alcnd_timedwait(alcnd_t *cond, almtx_t *mtx, const struct timespec *time_poi
 
     if(altimespec_get(&curtime, AL_TIME_UTC) != AL_TIME_UTC)
         return althrd_error;
-    sleeptime  = (time_point->tv_nsec - curtime.tv_nsec + 999999)/1000000;
-    sleeptime += (time_point->tv_sec - curtime.tv_sec)*1000;
+
+    if(curtime.tv_sec > time_point->tv_sec || (curtime.tv_sec == time_point->tv_sec &&
+                                               curtime.tv_nsec >= time_point->tv_nsec))
+        sleeptime = 0;
+    else
+    {
+        sleeptime  = (time_point->tv_nsec - curtime.tv_nsec + 999999)/1000000;
+        sleeptime += (time_point->tv_sec - curtime.tv_sec)*1000;
+    }
 
     IncrementRef(&icond->wait_count);
     LeaveCriticalSection(mtx);