perf daemon: Force waipid for all session on SIGCHLD delivery

If we don't process SIGCHLD before another comes, we will see just one
SIGCHLD as a result. In this case current code will miss exit
notification for a session and wait forever.

Adding extra waitpid check for all sessions when SIGCHLD is received, to
make sure we don't miss any session exit.

Also fix close condition for signal_fd.

Reported-by: Ian Rogers <irogers@google.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20210320221013.1619613-1-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/builtin-daemon.c b/tools/perf/builtin-daemon.c
index ace8772..4697493 100644 (file)
--- a/tools/perf/builtin-daemon.c
+++ b/tools/perf/builtin-daemon.c
@@ -402,35 +402,42 @@ static pid_t handle_signalfd(struct daemon *daemon)
        int status;
        pid_t pid;
 
+       /*
+        * Take signal fd data as pure signal notification and check all
+        * the sessions state. The reason is that multiple signals can get
+        * coalesced in kernel and we can receive only single signal even
+        * if multiple SIGCHLD were generated.
+        */
        err = read(daemon->signal_fd, &si, sizeof(struct signalfd_siginfo));
-       if (err != sizeof(struct signalfd_siginfo))
+       if (err != sizeof(struct signalfd_siginfo)) {
+               pr_err("failed to read signal fd\n");
                return -1;
+       }
 
        list_for_each_entry(session, &daemon->sessions, list) {
+               if (session->pid == -1)
+                       continue;
 
-               if (session->pid != (int) si.ssi_pid)
+               pid = waitpid(session->pid, &status, WNOHANG);
+               if (pid <= 0)
                        continue;
 
-               pid = waitpid(session->pid, &status, 0);
-               if (pid == session->pid) {
-                       if (WIFEXITED(status)) {
-                               pr_info("session '%s' exited, status=%d\n",
-                                       session->name, WEXITSTATUS(status));
-                       } else if (WIFSIGNALED(status)) {
-                               pr_info("session '%s' killed (signal %d)\n",
-                                       session->name, WTERMSIG(status));
-                       } else if (WIFSTOPPED(status)) {
-                               pr_info("session '%s' stopped (signal %d)\n",
-                                       session->name, WSTOPSIG(status));
-                       } else {
-                               pr_info("session '%s' Unexpected status (0x%x)\n",
-                                       session->name, status);
-                       }
+               if (WIFEXITED(status)) {
+                       pr_info("session '%s' exited, status=%d\n",
+                               session->name, WEXITSTATUS(status));
+               } else if (WIFSIGNALED(status)) {
+                       pr_info("session '%s' killed (signal %d)\n",
+                               session->name, WTERMSIG(status));
+               } else if (WIFSTOPPED(status)) {
+                       pr_info("session '%s' stopped (signal %d)\n",
+                               session->name, WSTOPSIG(status));
+               } else {
+                       pr_info("session '%s' Unexpected status (0x%x)\n",
+                               session->name, status);
                }
 
                session->state = KILL;
                session->pid = -1;
-               return pid;
        }
 
        return 0;
@@ -443,7 +450,6 @@ static int daemon_session__wait(struct daemon_session *session, struct daemon *d
                .fd     = daemon->signal_fd,
                .events = POLLIN,
        };
-       pid_t wpid = 0, pid = session->pid;
        time_t start;
 
        start = time(NULL);
@@ -452,7 +458,7 @@ static int daemon_session__wait(struct daemon_session *session, struct daemon *d
                int err = poll(&pollfd, 1, 1000);
 
                if (err > 0) {
-                       wpid = handle_signalfd(daemon);
+                       handle_signalfd(daemon);
                } else if (err < 0) {
                        perror("failed: poll\n");
                        return -1;
@@ -460,7 +466,7 @@ static int daemon_session__wait(struct daemon_session *session, struct daemon *d
 
                if (start + secs < time(NULL))
                        return -1;
-       } while (wpid != pid);
+       } while (session->pid != -1);
 
        return 0;
 }
@@ -1344,7 +1350,7 @@ out:
                close(sock_fd);
        if (conf_fd != -1)
                close(conf_fd);
-       if (conf_fd != -1)
+       if (signal_fd != -1)
                close(signal_fd);
 
        pr_info("daemon exited\n");