linux-kernel - Re: [PATCH 1/1] Improve kernfs_notify() poll notification latency

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Message-ID: <20181120161419.GS2509588@devbig004.ftw2.facebook.com>
Date:   Tue, 20 Nov 2018 08:14:19 -0800
From:   Tejun Heo <tj@...nel.org>
To:     Radu Rendec <radu.rendec@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH 1/1] Improve kernfs_notify() poll notification latency

On Thu, Nov 15, 2018 at 09:09:54PM -0500, Radu Rendec wrote:
> 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@...il.com>

Acked-by: Tejun Heo <tj@...nel.org>

Greg, can you please route this one?

Thanks.

-- 
tejun