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Re: [Qemu-devel] [PATCH v4 2/4] monitor: protect mon->fds with mon_lock
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [PATCH v4 2/4] monitor: protect mon->fds with mon_lock |
Date: |
Wed, 2 May 2018 12:15:07 +0100 |
User-agent: |
Mutt/1.9.5 (2018-04-13) |
* Peter Xu (address@hidden) 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 <address@hidden>
> ---
> 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.
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);
> 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 / address@hidden / Manchester, UK