linux-kernel - Re: [PATCH v2] ntb: Add mutex to make link_event

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Message-ID: <CABbqxmc+jkpgiHrWb5UH2FRZtaNpe4754qis=cPKtidW6+Vj6Q@mail.gmail.com>
Date: Wed, 3 Sep 2025 10:20:33 +0800
From: yuanli fu <fuyuanli0722@...il.com>
To: Dave Jiang <dave.jiang@...el.com>
Cc: jdmason@...zu.us, allenbh@...il.com, ntb@...ts.linux.dev, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] ntb: Add mutex to make link_event_callback executed linearly.

Dave Jiang <dave.jiang@...el.com> 于2025年8月25日周一 23:06写道：
>
>
>
> On 8/25/25 2:15 AM, fuyuanli wrote:
> > Since the CPU selected by schedule_work is uncertain, multiple link_event
> > callbacks may be executed at same time. For example, after peer's link is
> > up, it is down quickly before local link_work completed. If link_cleanup
> > is added to the workqueue of another CPU, then link_work and link_cleanup
> > may be executed at the same time. So add a mutex to prevent them from being
> > executed concurrently.
> >
> > Signed-off-by: fuyuanli <fuyuanli@...iglobal.com>
>
> Reviewed-by: Dave Jiang <dave.jiang@...el.com>

Hi Dave,

Hope you are doing well.

Just wanted to gently follow up on this patch which you had acked
before. Is there
anything else I can do to help get this merged? Perhaps it needs a rebase on a
different tree?

Thanks for your time and all your work!

Best regards,
Yuanli Fu


>
> > ---
> > v2:
> > 1) use guard() instead of lock & unlock functions.
> >
> > v1:
> > Link: https://lore.kernel.org/all/aKiBi4ZDlbgzed%2Fz@didi-ThinkCentre-M930t-N000/
> > ---
> >  drivers/ntb/ntb_transport.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> >
> > diff --git a/drivers/ntb/ntb_transport.c b/drivers/ntb/ntb_transport.c
> > index 4f775c3e218f..eb875e3db2e3 100644
> > --- a/drivers/ntb/ntb_transport.c
> > +++ b/drivers/ntb/ntb_transport.c
> > @@ -59,6 +59,7 @@
> >  #include <linux/slab.h>
> >  #include <linux/types.h>
> >  #include <linux/uaccess.h>
> > +#include <linux/mutex.h>
> >  #include "linux/ntb.h"
> >  #include "linux/ntb_transport.h"
> >
> > @@ -241,6 +242,9 @@ struct ntb_transport_ctx {
> >       struct work_struct link_cleanup;
> >
> >       struct dentry *debugfs_node_dir;
> > +
> > +     /* Make sure workq of link event be executed serially */
> > +     struct mutex link_event_lock;
> >  };
> >
> >  enum {
> > @@ -1024,6 +1028,7 @@ static void ntb_transport_link_cleanup_work(struct work_struct *work)
> >       struct ntb_transport_ctx *nt =
> >               container_of(work, struct ntb_transport_ctx, link_cleanup);
> >
> > +     guard(mutex)(&nt->link_event_lock);
> >       ntb_transport_link_cleanup(nt);
> >  }
> >
> > @@ -1047,6 +1052,8 @@ static void ntb_transport_link_work(struct work_struct *work)
> >       u32 val;
> >       int rc = 0, i, spad;
> >
> > +     guard(mutex)(&nt->link_event_lock);
> > +
> >       /* send the local info, in the opposite order of the way we read it */
> >
> >       if (nt->use_msi) {
>