processgroup: change the polling interval for killProcessGroup()

to make the function faster on average. Since killing a process
takes about 40-60ms on a recent device, the previous logic tends
to sleep too long. This CL does not significantly change the total
timeout (old code: 204ms, new code: 200ms).

Bug: 21813611
Change-Id: Ica44b2437ccccaebadcf585d7a09d993ce71a499

1 files changed, 4 insertions, 3 deletions

diff --git a/libprocessgroup/processgroup.cpp b/libprocessgroup/processgroup.cpp
index a80965fd0..ad0500dab 100644
--- a/libprocessgroup/processgroup.cpp
+++ b/libprocessgroup/processgroup.cpp
@@ -252,14 +252,15 @@ static int killProcessGroupOnce(uid_t uid, int initialPid, int signal)
 int killProcessGroup(uid_t uid, int initialPid, int signal)
 {
     int processes;
-    int sleep_us = 100;
+    const int sleep_us = 5 * 1000;  // 5ms
     int64_t startTime = android::uptimeMillis();
+    int retry = 40;
 
     while ((processes = killProcessGroupOnce(uid, initialPid, signal)) > 0) {
         SLOGV("killed %d processes for processgroup %d\n", processes, initialPid);
-        if (sleep_us < 128000) {
+        if (retry > 0) {
             usleep(sleep_us);
-            sleep_us *= 2;
+            --retry;
         } else {
             SLOGE("failed to kill %d processes for processgroup %d\n",
                     processes, initialPid);