commit 599d979126a0c60f5cc2955aedc58431f7659270
author T.J. Mercier <tjmercier@google.com> Thu Oct 26 20:46:21 2023 +0000
committer T.J. Mercier <tjmercier@google.com> Tue Oct 31 16:31:44 2023 +0000
tree 753e84100c1158d4b2be97027d98d65f2615754f
parent a93795deaeb0f11e16f225a48ed58044e35c5c13

libprocessgroup: Remove max_processes from KillProcessGroup API

The max_processes calculation is incorrect for KillProcessGroup because
the set of processes in cgroup.procs can differ between the multiple
reads in the implementation. Luckily the exact value isn't very
important because it's just logged. Remove max_processes from the API
and remove the warning about the new behavior in Android 11.

Note that we still always LOG(INFO) that any cgroup is being killed.

Bug: 301871933
Change-Id: I8e449f5089d4a48dbc1797b6d979539e87026f43

libprocessgroup/processgroup.cpp

diff --git a/libprocessgroup/processgroup.cpp b/libprocessgroup/processgroup.cpp
index cc2565f..3fa43f8 100644
--- a/libprocessgroup/processgroup.cpp
+++ b/libprocessgroup/processgroup.cpp
@@ -455,8 +455,7 @@
     return (!fd || feof(fd.get())) ? processes : -1;
 }
 
-static int KillProcessGroup(uid_t uid, int initialPid, int signal, int retries,
-                            int* max_processes) {
+static int KillProcessGroup(uid_t uid, int initialPid, int signal, int retries) {
     CHECK_GE(uid, 0);
     CHECK_GT(initialPid, 0);
 
@@ -468,16 +467,9 @@
 
     std::chrono::steady_clock::time_point start = std::chrono::steady_clock::now();
 
-    if (max_processes != nullptr) {
-        *max_processes = 0;
-    }
-
     int retry = retries;
     int processes;
     while ((processes = DoKillProcessGroupOnce(cgroup, uid, initialPid, signal)) > 0) {
-        if (max_processes != nullptr && processes > *max_processes) {
-            *max_processes = processes;
-        }
         LOG(VERBOSE) << "Killed " << processes << " processes for processgroup " << initialPid;
         if (!CgroupsAvailable()) {
             // makes no sense to retry, because there are no cgroup_procs file
@@ -540,12 +532,12 @@
     }
 }
 
-int killProcessGroup(uid_t uid, int initialPid, int signal, int* max_processes) {
-    return KillProcessGroup(uid, initialPid, signal, 40 /*retries*/, max_processes);
+int killProcessGroup(uid_t uid, int initialPid, int signal) {
+    return KillProcessGroup(uid, initialPid, signal, 40 /*retries*/);
 }
 
-int killProcessGroupOnce(uid_t uid, int initialPid, int signal, int* max_processes) {
-    return KillProcessGroup(uid, initialPid, signal, 0 /*retries*/, max_processes);
+int killProcessGroupOnce(uid_t uid, int initialPid, int signal) {
+    return KillProcessGroup(uid, initialPid, signal, 0 /*retries*/);
 }
 
 int sendSignalToProcessGroup(uid_t uid, int initialPid, int signal) {