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[Qemu-devel] [PATCH v2 for-3.0] tests/libqtest: Improve kill_qemu()


From: Eric Blake
Subject: [Qemu-devel] [PATCH v2 for-3.0] tests/libqtest: Improve kill_qemu()
Date: Mon, 23 Jul 2018 14:35:30 -0500

In kill_qemu() we have an assert that checks that the QEMU process
didn't dump core:
            assert(!WCOREDUMP(wstatus));

Unfortunately the WCOREDUMP macro here means the resulting message
is not very easy to comprehend on at least some systems:

ahci-test: tests/libqtest.c:113: kill_qemu: Assertion `!(((__extension__ 
(((union { __typeof(wstatus) __in; int __i; }) { .__in = (wstatus) }).__i))) & 
0x80)' failed.

and it doesn't identify what signal the process took.

Furthermore, we are NOT detecting EINTR (while EINTR shouldn't be
happening if we didn't install signal handlers, it's still better
to always be robust), and also want to log unexpected non-zero status
that was not accompanied by a core dump.

Instead of using a raw assert, print the information in an
easier to understand way:

/i386/ahci/sanity: tests/libqtest.c:119: kill_qemu() detected QEMU death with 
core dump from signal 11 (Segmentation fault)
Aborted (core dumped)

(Of course, the really useful information would be why the QEMU
process dumped core in the first place, but we don't have that
by the time the test program has picked up the exit status.)

Suggested-by: Peter Maydell <address@hidden>
Signed-off-by: Eric Blake <address@hidden>
---

I've taken the ideas from Peter's patch:
https://lists.gnu.org/archive/html/qemu-devel/2018-07/msg04430.html
as well as fixing a related issue brought up last time this was touched:
https://lists.gnu.org/archive/html/qemu-devel/2018-05/msg05710.html

 tests/libqtest.c | 39 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 37 insertions(+), 2 deletions(-)

diff --git a/tests/libqtest.c b/tests/libqtest.c
index 098af6aec44..f3dabfadd78 100644
--- a/tests/libqtest.c
+++ b/tests/libqtest.c
@@ -105,12 +105,47 @@ static void kill_qemu(QTestState *s)
     if (s->qemu_pid != -1) {
         int wstatus = 0;
         pid_t pid;
+        bool die = false;

         kill(s->qemu_pid, SIGTERM);
+    retry:
         pid = waitpid(s->qemu_pid, &wstatus, 0);
+        if (pid == -1 && errno == EINTR) {
+            goto retry;
+        }

-        if (pid == s->qemu_pid && WIFSIGNALED(wstatus)) {
-            assert(!WCOREDUMP(wstatus));
+        assert(pid == s->qemu_pid);
+        /*
+         * We expect qemu to exit with status 0; anything else is
+         * fishy and should be logged.  Abort except when death by
+         * signal is not accompanied by a coredump (as that's the only
+         * time it was likely that the user is trying to kill the
+         * testsuite early).
+         */
+        if (wstatus) {
+            die = true;
+            if (WIFEXITED(wstatus)) {
+                fprintf(stderr, "%s:%d: kill_qemu() tried to terminate QEMU "
+                        "process but encountered exit status %d\n",
+                        __FILE__, __LINE__, WEXITSTATUS(wstatus));
+            } else if (WIFSIGNALED(wstatus)) {
+                int sig = WTERMSIG(wstatus);
+                const char *signame = strsignal(sig) ?: "unknown ???";
+
+                if (!WCOREDUMP(wstatus)) {
+                    die = false;
+                    fprintf(stderr, "%s:%d: kill_qemu() ignoring QEMU death "
+                            "by signal %d (%s)\n",
+                            __FILE__, __LINE__, sig, signame);
+                } else {
+                    fprintf(stderr, "%s:%d: kill_qemu() detected QEMU death "
+                            "with core dump from signal %d (%s)\n",
+                            __FILE__, __LINE__, sig, signame);
+                }
+            }
+        }
+        if (die) {
+            abort();
         }
     }
 }
-- 
2.14.4




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