linux-kernel - Re: [RFC PATCH 02/21] Add a prelocked wake-up

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Date:   Tue, 15 Oct 2019 15:14:10 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     David Howells <dhowells@...hat.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Kan Liang <kan.liang@...el.com>
Cc:     Casey Schaufler <casey@...aufler-ca.com>,
        Stephen Smalley <sds@...ho.nsa.gov>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Nicolas Dichtel <nicolas.dichtel@...nd.com>, raven@...maw.net,
        Christian Brauner <christian@...uner.io>,
        keyrings@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-block <linux-block@...r.kernel.org>,
        LSM List <linux-security-module@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 02/21] Add a prelocked wake-up

On Tue, Oct 15, 2019 at 2:48 PM David Howells <dhowells@...hat.com> wrote:
>
> Add a wakeup call for a case whereby the caller already has the waitqueue
> spinlock held.

That naming is crazy.

We already have helper functions like this, and they are just called
"wake_up_locked()".

So the "prelocked" naming is just odd. Make it be
wake_up_interruptible_sync_poll_locked().

The helper function should likely be

  void __wake_up_locked_sync_key(struct wait_queue_head *wq_head,
unsigned int mode, void *key)
  {
        __wake_up_common(wq_head, mode, 1, WF_SYNC, key, NULL);
  }
  EXPORT_SYMBOL_GPL(__wake_up_locked_sync_key);

to match the other naming patterns there.

[ Unrelated ]

Looking at that mess of functions, I also wonder if we should try to
just remove the bookmark code again. It was cute, and it was useful,
but I think the problem with the page lock list may have been fixed by
commit 9a1ea439b16b ("mm: put_and_wait_on_page_locked() while page is
migrated") which avoids the retry condition with
migrate_page_move_mapping().

Tim/Kan? Do you have the problematic load still?

              Linus