surfaceflinger: use Mutex timedLock instead of tryLock loop

Rather than trying to acquire the state lock without waiting three
times at 1 second intervals in SurfaceFlinger::dump(), just try to
acquire the lock once with a 1 second timeout. Avoids spurious mutex
acquire failures that lead to flaky
com.android.cts.jank.opengl.CtsHostJankOpenGl results.

Bug: 18842510
Change-Id: I00ce6109647de2aef8831dd2f8fa98652ba7f4e0

1 files changed, 6 insertions, 9 deletions

diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index 8daf0f9..6a5a39e 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -2359,18 +2359,15 @@ status_t SurfaceFlinger::dump(int fd, const Vector<String16>& args)
         result.appendFormat("Permission Denial: "
                 "can't dump SurfaceFlinger from pid=%d, uid=%d\n", pid, uid);
     } else {
-        // Try to get the main lock, but don't insist if we can't
+        // Try to get the main lock, but give up after one second
         // (this would indicate SF is stuck, but we want to be able to
         // print something in dumpsys).
-        int retry = 3;
-        while (mStateLock.tryLock()<0 && --retry>=0) {
-            usleep(1000000);
-        }
-        const bool locked(retry >= 0);
+        status_t err = mStateLock.timedLock(s2ns(1));
+        bool locked = (err == NO_ERROR);
         if (!locked) {
-            result.append(
-                    "SurfaceFlinger appears to be unresponsive, "
-                    "dumping anyways (no locks held)\n");
+            result.appendFormat(
+                    "SurfaceFlinger appears to be unresponsive (%s [%d]), "
+                    "dumping anyways (no locks held)\n", strerror(-err), err);
         }
 
         bool dumpAll = true;