On Wed, May 02, 2018 at 12:15:07PM +0100, Dr. David Alan Gilbert wrote:
> * Peter Xu (pet...@redhat.com) wrote:
> > mon->fds were protected by BQL. Now protect it by mon_lock so that it
> > can even be used in monitor iothread.
> >
> > Signed-off-by: Peter Xu <pet...@redhat.com>
> > ---
> > monitor.c | 11 ++++++++++-
> > 1 file changed, 10 insertions(+), 1 deletion(-)
> >
> > diff --git a/monitor.c b/monitor.c
> > index 48882d28ae..9f361ec21e 100644
> > --- a/monitor.c
> > +++ b/monitor.c
> > @@ -213,7 +213,6 @@ struct Monitor {
> > BlockCompletionFunc *password_completion_cb;
> > void *password_opaque;
> > mon_cmd_t *cmd_table;
> > - QLIST_HEAD(,mon_fd_t) fds;
> > QTAILQ_ENTRY(Monitor) entry;
> >
> > /*
> > @@ -225,6 +224,7 @@ struct Monitor {
> > /*
> > * Fields that are protected by the per-monitor lock.
> > */
> > + QLIST_HEAD(, mon_fd_t) fds;
> > QString *outbuf;
> > guint out_watch;
> > /* Read under either BQL or mon_lock, written with BQL+mon_lock. */
> > @@ -2207,6 +2207,7 @@ void qmp_getfd(const char *fdname, Error **errp)
> > return;
> > }
> >
> > + qemu_mutex_lock(&cur_mon->mon_lock);
> > QLIST_FOREACH(monfd, &cur_mon->fds, next) {
> > if (strcmp(monfd->name, fdname) != 0) {
> > continue;
> > @@ -2214,6 +2215,7 @@ void qmp_getfd(const char *fdname, Error **errp)
> >
> > close(monfd->fd);
> > monfd->fd = fd;
> > + qemu_mutex_unlock(&cur_mon->mon_lock);
>
> Why is it safe to have a close() in a mon_lock'd region?
> We've got to make sure everything that happens in it is non-blocking.
Hmm indeed. Let me move that close() out of the critical section. I
think I need to touch up below [1] too since it'll has similar
problem.
I'll wait for some more comments to repost. Thanks,
>
> Dave
>
> > return;
> > }
> >
> > @@ -2222,12 +2224,14 @@ void qmp_getfd(const char *fdname, Error **errp)
> > monfd->fd = fd;
> >
> > QLIST_INSERT_HEAD(&cur_mon->fds, monfd, next);
> > + qemu_mutex_unlock(&cur_mon->mon_lock);
> > }
> >
> > void qmp_closefd(const char *fdname, Error **errp)
> > {
> > mon_fd_t *monfd;
> >
> > + qemu_mutex_lock(&cur_mon->mon_lock);
> > QLIST_FOREACH(monfd, &cur_mon->fds, next) {
> > if (strcmp(monfd->name, fdname) != 0) {
> > continue;
> > @@ -2237,9 +2241,11 @@ void qmp_closefd(const char *fdname, Error **errp)
> > close(monfd->fd);
> > g_free(monfd->name);
> > g_free(monfd);
> > + qemu_mutex_unlock(&cur_mon->mon_lock);
[1]
> > return;
> > }
> >
> > + qemu_mutex_unlock(&cur_mon->mon_lock);
> > error_setg(errp, QERR_FD_NOT_FOUND, fdname);
> > }
> >
> > @@ -2247,6 +2253,7 @@ int monitor_get_fd(Monitor *mon, const char *fdname,
> > Error **errp)
> > {
> > mon_fd_t *monfd;
> >
> > + qemu_mutex_lock(&mon->mon_lock);
> > QLIST_FOREACH(monfd, &mon->fds, next) {
> > int fd;
> >
> > @@ -2260,10 +2267,12 @@ int monitor_get_fd(Monitor *mon, const char
> > *fdname, Error **errp)
> > QLIST_REMOVE(monfd, next);
> > g_free(monfd->name);
> > g_free(monfd);
> > + qemu_mutex_unlock(&mon->mon_lock);
> >
> > return fd;
> > }
> >
> > + qemu_mutex_unlock(&mon->mon_lock);
> > error_setg(errp, "File descriptor named '%s' has not been found",
> > fdname);
> > return -1;
> > }
> > --
> > 2.14.3
> >
> --
> Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
--
Peter Xu
