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authorPaolo Bonzini <pbonzini@redhat.com>2014-07-11 12:11:38 +0200
committerPaolo Bonzini <pbonzini@redhat.com>2014-07-14 16:13:58 +0200
commit7b3621f47a990c5099c6385728347f69a8d0e55c (patch)
treed75c25a8074676f333cb5e69a38b10b1ea5784b8
parent2039511b8f573165420c86380762ae829dc398d9 (diff)
downloadhqemu-7b3621f47a990c5099c6385728347f69a8d0e55c.zip
hqemu-7b3621f47a990c5099c6385728347f69a8d0e55c.tar.gz
qemu-char: fix deadlock with "-monitor pty"
qemu_chr_be_generic_open cannot be called with the write lock taken, because it calls client code that may call qemu_chr_fe_write. This actually happens for the monitor: 0x00007ffff27dbf79 in __GI_raise (sig=sig@entry=6) 0x00007ffff27df388 in __GI_abort () 0x00005555555ef489 in error_exit (err=<optimized out>, msg=msg@entry=0x5555559796d0 <__func__.5959> "qemu_mutex_lock") 0x00005555558f9080 in qemu_mutex_lock (mutex=mutex@entry=0x555556248a30) 0x0000555555713936 in qemu_chr_fe_write (s=0x555556248a30, buf=buf@entry=0x5555563d8870 "QEMU 2.0.90 monitor - type 'help' for more information\r\n", len=56) 0x00005555556217fd in monitor_flush_locked (mon=mon@entry=0x555556251fd0) 0x0000555555621a12 in monitor_flush_locked (mon=0x555556251fd0) monitor_puts (mon=mon@entry=0x555556251fd0, str=0x55555634bfa7 "", str@entry=0x55555634bf70 "QEMU 2.0.90 monitor - type 'help' for more information\n") 0x0000555555624359 in monitor_vprintf (mon=0x555556251fd0, fmt=<optimized out>, ap=<optimized out>) 0x0000555555624414 in monitor_printf (mon=<optimized out>, fmt=fmt@entry=0x5555559105a0 "QEMU %s monitor - type 'help' for more information\n") 0x0000555555629806 in monitor_event (opaque=0x555556251fd0, event=<optimized out>) 0x000055555571343c in qemu_chr_be_generic_open (s=0x555556248a30) To avoid this, defer the call to an idle callback, which will be called as soon as the main loop is re-entered. In order to simplify the cleanup and do it in one place only, change pty_chr_close to call pty_chr_state. To reproduce, run with "-monitor pty", then try to read from the slave /dev/pts/FOO that it creates. Fixes: 9005b2a7589540a3733b3abdcfbccfe7746cd1a1 Reported-by: Li Liang <liangx.z.li@intel.com> Reviewed-by: Fam Zheng <famz@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
-rw-r--r--qemu-char.c23
1 files changed, 21 insertions, 2 deletions
diff --git a/qemu-char.c b/qemu-char.c
index 55e372c..7acc03f 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -1089,6 +1089,7 @@ typedef struct {
/* Protected by the CharDriverState chr_write_lock. */
int connected;
guint timer_tag;
+ guint open_tag;
} PtyCharDriver;
static void pty_chr_update_read_handler_locked(CharDriverState *chr);
@@ -1101,6 +1102,7 @@ static gboolean pty_chr_timer(gpointer opaque)
qemu_mutex_lock(&chr->chr_write_lock);
s->timer_tag = 0;
+ s->open_tag = 0;
if (!s->connected) {
/* Next poll ... */
pty_chr_update_read_handler_locked(chr);
@@ -1203,12 +1205,26 @@ static gboolean pty_chr_read(GIOChannel *chan, GIOCondition cond, void *opaque)
return TRUE;
}
+static gboolean qemu_chr_be_generic_open_func(gpointer opaque)
+{
+ CharDriverState *chr = opaque;
+ PtyCharDriver *s = chr->opaque;
+
+ s->open_tag = 0;
+ qemu_chr_be_generic_open(chr);
+ return FALSE;
+}
+
/* Called with chr_write_lock held. */
static void pty_chr_state(CharDriverState *chr, int connected)
{
PtyCharDriver *s = chr->opaque;
if (!connected) {
+ if (s->open_tag) {
+ g_source_remove(s->open_tag);
+ s->open_tag = 0;
+ }
remove_fd_in_watch(chr);
s->connected = 0;
/* (re-)connect poll interval for idle guests: once per second.
@@ -1221,8 +1237,9 @@ static void pty_chr_state(CharDriverState *chr, int connected)
s->timer_tag = 0;
}
if (!s->connected) {
+ g_assert(s->open_tag == 0);
s->connected = 1;
- qemu_chr_be_generic_open(chr);
+ s->open_tag = g_idle_add(qemu_chr_be_generic_open_func, chr);
}
if (!chr->fd_in_tag) {
chr->fd_in_tag = io_add_watch_poll(s->fd, pty_chr_read_poll,
@@ -1236,7 +1253,8 @@ static void pty_chr_close(struct CharDriverState *chr)
PtyCharDriver *s = chr->opaque;
int fd;
- remove_fd_in_watch(chr);
+ qemu_mutex_lock(&chr->chr_write_lock);
+ pty_chr_state(chr, 0);
fd = g_io_channel_unix_get_fd(s->fd);
g_io_channel_unref(s->fd);
close(fd);
@@ -1244,6 +1262,7 @@ static void pty_chr_close(struct CharDriverState *chr)
g_source_remove(s->timer_tag);
s->timer_tag = 0;
}
+ qemu_mutex_unlock(&chr->chr_write_lock);
g_free(s);
qemu_chr_be_event(chr, CHR_EVENT_CLOSED);
}
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