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authorRadu Rendec <radu.rendec@gmail.com>2018-11-15 21:09:54 -0500
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-11-27 11:59:33 +0100
commit03c0a9208bb10821e5e3f1c81e6218df32524311 (patch)
tree7635fbc93182d6ebff9b7788f90c022c236eb5aa /fs/kernfs
parent6be244dcd59b01245394b62a128901b1cfec468c (diff)
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kernfs: Improve kernfs_notify() poll notification latency
kernfs_notify() does two notifications: poll and fsnotify. Originally, both notifications were done from scheduled work context and all that kernfs_notify() did was schedule the work. This patch simply moves the poll notification from the scheduled work handler to kernfs_notify(). The fsnotify notification still needs to be done from scheduled work context because it can sleep (it needs to lock a mutex). If the poll notification is time critical (the notified thread needs to wake as quickly as possible), it's better to do it from kernfs_notify() directly. One example is calling sysfs_notify_dirent() from a hardware interrupt handler to wake up a thread and handle the interrupt in user space. Signed-off-by: Radu Rendec <radu.rendec@gmail.com> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs/kernfs')
-rw-r--r--fs/kernfs/file.c23
1 files changed, 11 insertions, 12 deletions
diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index dbf5bc250bfd..f8d5021a652e 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -857,7 +857,6 @@ static __poll_t kernfs_fop_poll(struct file *filp, poll_table *wait)
static void kernfs_notify_workfn(struct work_struct *work)
{
struct kernfs_node *kn;
- struct kernfs_open_node *on;
struct kernfs_super_info *info;
repeat:
/* pop one off the notify_list */
@@ -871,17 +870,6 @@ repeat:
kn->attr.notify_next = NULL;
spin_unlock_irq(&kernfs_notify_lock);
- /* kick poll */
- spin_lock_irq(&kernfs_open_node_lock);
-
- on = kn->attr.open;
- if (on) {
- atomic_inc(&on->event);
- wake_up_interruptible(&on->poll);
- }
-
- spin_unlock_irq(&kernfs_open_node_lock);
-
/* kick fsnotify */
mutex_lock(&kernfs_mutex);
@@ -934,10 +922,21 @@ void kernfs_notify(struct kernfs_node *kn)
{
static DECLARE_WORK(kernfs_notify_work, kernfs_notify_workfn);
unsigned long flags;
+ struct kernfs_open_node *on;
if (WARN_ON(kernfs_type(kn) != KERNFS_FILE))
return;
+ /* kick poll immediately */
+ spin_lock_irqsave(&kernfs_open_node_lock, flags);
+ on = kn->attr.open;
+ if (on) {
+ atomic_inc(&on->event);
+ wake_up_interruptible(&on->poll);
+ }
+ spin_unlock_irqrestore(&kernfs_open_node_lock, flags);
+
+ /* schedule work to kick fsnotify */
spin_lock_irqsave(&kernfs_notify_lock, flags);
if (!kn->attr.notify_next) {
kernfs_get(kn);