[Qemu-devel] [PATCH 3/9] log: improve code in do_qemu_set_log

["Denis V. Lunev" <den@openvz.org>]

The following commit
    commit 96c33a4523ee1abe382ce4ff3e82b90ba78aa186
    Author: Dimitris Aragiorgis <dimara@arrikto.com>
    Date:   Thu Feb 18 13:38:38 2016 +0200

    log: Redirect stderr to logfile if deamonized
was created with unnecessary side effect - connect from libvirt starts
to hang. This, in turn, was fixed by
    commit c586eac33670c198c6c9ceb1419aa99dafcce907
    Author: Paolo Bonzini <pbonzini@redhat.com>
    Date:   Mon Feb 29 12:18:40 2016 +0100

    log: do not log if QEMU is daemonized but without -D
but the fix seems a bit awkward to me.

This patch fixes the problem with a bit more readable approach and makes the
code closer to the original state.

Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Stefan Hajnoczi <stefanha@redhat.com>
CC: Paolo Bonzini <pbonzini@redhat.com>
---
 include/qemu/log.h |  4 ++++
 os-posix.c         |  2 +-
 util/log.c         | 10 ++--------
 3 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/include/qemu/log.h b/include/qemu/log.h
index 40c24fd..be20811 100644
--- a/include/qemu/log.h
+++ b/include/qemu/log.h
@@ -88,6 +88,10 @@ static inline void qemu_log_close(void)
         }
         qemu_logfile = NULL;
     }
+
+    if (is_daemonized()) {
+        dup2(STDOUT_FILENO, STDERR_FILENO); /* dup /dev/null to stderr */
+    }
 }
 
 /* define log items */
diff --git a/os-posix.c b/os-posix.c
index 92fa3ba..d4b2a91 100644
--- a/os-posix.c
+++ b/os-posix.c
@@ -277,7 +277,7 @@ void os_setup_post(void)
         dup2(fd, 0);
         dup2(fd, 1);
         /* In case -D is given do not redirect stderr to /dev/null */
-        if (!qemu_logfile) {
+        if (!qemu_logfile || qemu_logfile == stderr) {
             dup2(fd, 2);
         }
 
diff --git a/util/log.c b/util/log.c
index 8b921de..a06aa14 100644
--- a/util/log.c
+++ b/util/log.c
@@ -56,8 +56,7 @@ void do_qemu_set_log(int log_flags, bool use_own_buffers)
 #ifdef CONFIG_TRACE_LOG
     qemu_loglevel |= LOG_TRACE;
 #endif
-    if (!qemu_logfile &&
-        (is_daemonized() ? logfilename != NULL : qemu_loglevel)) {
+    if (qemu_loglevel && !qemu_logfile) {
         if (logfilename) {
             qemu_logfile = fopen(logfilename, log_append ? "a" : "w");
             if (!qemu_logfile) {
@@ -67,13 +66,9 @@ void do_qemu_set_log(int log_flags, bool use_own_buffers)
             /* In case we are a daemon redirect stderr to logfile */
             if (is_daemonized()) {
                 dup2(fileno(qemu_logfile), STDERR_FILENO);
-                fclose(qemu_logfile);
-                /* This will skip closing logfile in qemu_log_close() */
-                qemu_logfile = stderr;
             }
         } else {
             /* Default to stderr if no log file specified */
-            assert(!is_daemonized());
             qemu_logfile = stderr;
         }
         /* must avoid mmap() usage of glibc by setting a buffer "by hand" */
@@ -91,8 +86,7 @@ void do_qemu_set_log(int log_flags, bool use_own_buffers)
             log_append = 1;
         }
     }
-    if (qemu_logfile &&
-        (is_daemonized() ? logfilename == NULL : !qemu_loglevel)) {
+    if (!qemu_loglevel && qemu_logfile) {
         qemu_log_close();
     }
 }
-- 
2.5.0