async: aio_context_new(): Handle event_notifier_init failure

On a system with a low limit of open files the initialization
of the event notifier could fail and QEMU exits without printing any
error information to the user.

The problem can be easily reproduced by enforcing a low limit of open
files and start QEMU with enough I/O threads to hit this limit.

The same problem raises, without the creation of I/O threads, while
QEMU initializes the main event loop by enforcing an even lower limit of
open files.

This commit adds an error message on failure:

 # qemu [...] -object iothread,id=iothread0 -object iothread,id=iothread1
 qemu: Failed to initialize event notifier: Too many open files in system

Signed-off-by: Chrysostomos Nanakos <cnanakos@grnet.gr>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/vl.c b/vl.c
index dc792fe08b..6d073c3576 100644
--- a/vl.c
+++ b/vl.c
@@ -2968,6 +2968,7 @@ int main(int argc, char **argv, char **envp)
     ram_addr_t maxram_size = default_ram_size;
     uint64_t ram_slots = 0;
     FILE *vmstate_dump_file = NULL;
+    Error *main_loop_err = NULL;
 
     atexit(qemu_run_exit_notifiers);
     error_set_progname(argv[0]);
@@ -3998,8 +3999,8 @@ int main(int argc, char **argv, char **envp)
 
     os_daemonize();
 
-    if (qemu_init_main_loop()) {
-        fprintf(stderr, "qemu_init_main_loop failed\n");
+    if (qemu_init_main_loop(&main_loop_err)) {
+        error_report("%s", error_get_pretty(main_loop_err));
         exit(1);
     }