Bug 1829026 - Handle KERN_ABORTED from semaphore_wait. r=aosmond

semaphore_wait and semaphore_timedwait can return KERN_ABORTED, much
like POSIX semaphores can return EINTR, and need to restart their
waits for correct behavior.

Differential Revision: https://phabricator.services.mozilla.com/D195952

ipc/glue/CrossProcessSemaphore_mach.cpp

@@ -7,6 +7,7 @@
 #include "CrossProcessSemaphore.h"
 #include "nsDebug.h"
 #include "nsISupportsImpl.h"
+#include <mach/mach_time.h>
 
 static const uint64_t kNsPerUs = 1000;
 static const uint64_t kNsPerSec = 1000000000;
@@ -47,14 +48,33 @@ CrossProcessSemaphore::~CrossProcessSemaphore() {
 
 bool CrossProcessSemaphore::Wait(const Maybe<TimeDuration>& aWaitTime) {
   MOZ_ASSERT(mSemaphore, "Improper construction of semaphore.");
+  int kr = KERN_OPERATION_TIMED_OUT;
+  // semaphore_(timed)wait may be interrupted by KERN_ABORTED. Carefully restart
+  // the wait until it either succeeds or times out.
   if (aWaitTime.isNothing()) {
-    return semaphore_wait(mSemaphore.get()) == KERN_SUCCESS;
+    do {
+      kr = semaphore_wait(mSemaphore.get());
+    } while (kr == KERN_ABORTED);
+  } else {
+    mach_timebase_info_data_t tb;
+    if (mach_timebase_info(&tb) != KERN_SUCCESS) {
+      return false;
+    }
+    uint64_t now = (mach_absolute_time() * tb.numer) / tb.denom;
+    uint64_t deadline = now + uint64_t(kNsPerUs * aWaitTime->ToMicroseconds());
+    while (now <= deadline) {
+      uint64_t ns = deadline - now;
+      mach_timespec_t ts;
+      ts.tv_sec = ns / kNsPerSec;
+      ts.tv_nsec = ns % kNsPerSec;
+      kr = semaphore_timedwait(mSemaphore.get(), ts);
+      if (kr != KERN_ABORTED) {
+        break;
+      }
+      now = (mach_absolute_time() * tb.numer) / tb.denom;
+    }
   }
-  uint64_t ns = uint64_t(kNsPerUs * aWaitTime->ToMicroseconds());
-  mach_timespec_t ts;
-  ts.tv_sec = ns / kNsPerSec;
-  ts.tv_nsec = ns % kNsPerSec;
-  return semaphore_timedwait(mSemaphore.get(), ts) == KERN_SUCCESS;
+  return kr == KERN_SUCCESS;
 }
 
 void CrossProcessSemaphore::Signal() {