commit d2da814d1fd146c49117d8e940d0331f751ca086
author Jim Blackler <jimblackler@google.com> Tue Sep 10 15:30:05 2019 +0100
committer Suren Baghdasaryan <surenb@google.com> Thu Sep 26 16:27:03 2019 -0700
tree d23f4871a64beedc7ba8a11dd9b8b7fd2c13ac66
parent f0d17fb50ed749b577998618022b74b184d617b1

lmkd: Maintain pid to taskname mapping to amend kill reports.

Required because the kernel cannot always get the taskname safely at
the time the process is killed (due to competition for mm->mmap_sem).

Test: manually
Bug: 130017100
Signed-off-by: Jim Blackler <jimblackler@google.com>
Change-Id: I27a2c3340da321570f0832d58fe9e79ca031620b

lmkd/lmkd.c

diff --git a/lmkd/lmkd.c b/lmkd/lmkd.c
index d17da12..f06717d 100644
--- a/lmkd/lmkd.c
+++ b/lmkd/lmkd.c
@@ -362,6 +362,9 @@
 /* PAGE_SIZE / 1024 */
 static long page_k;
 
+static char* proc_get_name(int pid);
+static void poll_kernel();
+
 static bool parse_int64(const char* str, int64_t* ret) {
     char* endptr;
     long long val = strtoll(str, &endptr, 10);
@@ -634,6 +637,9 @@
     }
 
     if (use_inkernel_interface) {
+#ifdef LMKD_LOG_STATS
+        stats_store_taskname(params.pid, proc_get_name(params.pid));
+#endif
         return;
     }
 
@@ -704,6 +710,16 @@
     struct lmk_procremove params;
 
     if (use_inkernel_interface) {
+#ifdef LMKD_LOG_STATS
+        /* Perform an extra check before the pid is removed, after which it
+         * will be impossible for poll_kernel to get the taskname. poll_kernel()
+         * is potentially a long-running blocking function; however this method
+         * handles AMS requests but does not block AMS.*/
+        if (enable_stats_log) {
+            poll_kernel();
+        }
+        stats_remove_taskname(params.pid);
+#endif
         return;
     }
 
@@ -721,6 +737,9 @@
     struct proc *next;
 
     if (use_inkernel_interface) {
+#ifdef LMKD_LOG_STATS
+        stats_purge_tasknames();
+#endif
         return;
     }
 
@@ -1925,7 +1944,6 @@
 
 #ifdef LMKD_LOG_STATS
 static int kernel_poll_fd = -1;
-
 static void poll_kernel() {
     if (kernel_poll_fd == -1) {
         // not waiting
@@ -1958,9 +1976,9 @@
         /* only the death of the group leader process is logged */
         if (fields_read == 10 && group_leader_pid == pid) {
             int64_t process_start_time_ns = starttime * (NS_PER_SEC / sysconf(_SC_CLK_TCK));
-            stats_write_lmk_kill_occurred(log_ctx, LMK_KILL_OCCURRED, uid, taskname, oom_score_adj,
-                                          min_flt, maj_flt, rss_in_pages * PAGE_SIZE, 0, 0,
-                                          process_start_time_ns, min_score_adj);
+            stats_write_lmk_kill_occurred_pid(log_ctx, LMK_KILL_OCCURRED, uid, pid, oom_score_adj,
+                                              min_flt, maj_flt, rss_in_pages * PAGE_SIZE, 0, 0,
+                                              process_start_time_ns, min_score_adj);
         }
 
         free(taskname);