On 17.12.20 09:17, SeongJae Park wrote:
From: SeongJae Park <sjpark@xxxxxxxxx> This commit adds a counter of pending messages for each watch in the struct. It is used to skip unnecessary pending messages lookup in 'unregister_xenbus_watch()'. It could also be used in 'will_handle' callback. This is part of XSA-349 This is upstream commit 3dc86ca6b4c8cfcba9da7996189d1b5a358a94fc Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: SeongJae Park <sjpark@xxxxxxxxx> Reported-by: Michael Kurth <mku@xxxxxxxxx> Reported-by: Pawel Wieczorkiewicz <wipawel@xxxxxxxxx> Signed-off-by: Author Redacted <security@xxxxxxx> Reviewed-by: Juergen Gross <jgross@xxxxxxxx> Signed-off-by: Juergen Gross <jgross@xxxxxxxx> --- drivers/xen/xenbus/xenbus_xs.c | 30 ++++++++++++++++++------------ include/xen/xenbus.h | 2 ++ 2 files changed, 20 insertions(+), 12 deletions(-) diff --git a/drivers/xen/xenbus/xenbus_xs.c b/drivers/xen/xenbus/xenbus_xs.c index 0ea1c259f2f1..420d478e1708 100644 --- a/drivers/xen/xenbus/xenbus_xs.c +++ b/drivers/xen/xenbus/xenbus_xs.c @@ -701,6 +701,8 @@ int register_xenbus_watch(struct xenbus_watch *watch)sprintf(token, "%lX", (long)watch); + watch->nr_pending = 0;+
I'm missing the incrementing of nr_pending, which was present in the upstream patch. Juergen
down_read(&xs_state.watch_mutex);spin_lock(&watches_lock);@@ -750,12 +752,15 @@ void unregister_xenbus_watch(struct xenbus_watch *watch)/* Cancel pending watch events. */spin_lock(&watch_events_lock); - list_for_each_entry_safe(msg, tmp, &watch_events, list) { - if (msg->u.watch.handle != watch) - continue; - list_del(&msg->list); - kfree(msg->u.watch.vec); - kfree(msg); + if (watch->nr_pending) { + list_for_each_entry_safe(msg, tmp, &watch_events, list) { + if (msg->u.watch.handle != watch) + continue; + list_del(&msg->list); + kfree(msg->u.watch.vec); + kfree(msg); + } + watch->nr_pending = 0; } spin_unlock(&watch_events_lock);@@ -802,7 +807,6 @@ void xs_suspend_cancel(void) static int xenwatch_thread(void *unused){ - struct list_head *ent; struct xs_stored_msg *msg;for (;;) {@@ -815,13 +819,15 @@ static int xenwatch_thread(void *unused) mutex_lock(&xenwatch_mutex);spin_lock(&watch_events_lock);- ent = watch_events.next; - if (ent != &watch_events) - list_del(ent); + msg = list_first_entry_or_null(&watch_events, + struct xs_stored_msg, list); + if (msg) { + list_del(&msg->list); + msg->u.watch.handle->nr_pending--; + } spin_unlock(&watch_events_lock);- if (ent != &watch_events) {- msg = list_entry(ent, struct xs_stored_msg, list); + if (msg) { msg->u.watch.handle->callback( msg->u.watch.handle, (const char **)msg->u.watch.vec, diff --git a/include/xen/xenbus.h b/include/xen/xenbus.h index 1772507dc2c9..ed9e7e3307b7 100644 --- a/include/xen/xenbus.h +++ b/include/xen/xenbus.h @@ -58,6 +58,8 @@ struct xenbus_watch /* Path being watched. */ const char *node;+ unsigned int nr_pending;+ /* * Called just before enqueing new event while a spinlock is held. * The event will be discarded if this callback returns false.
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