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

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Message-ID: <f755b775-b87a-4a3f-b7b9-f37cdadf21e3@intel.com>
Date: Wed, 3 Sep 2025 08:26:21 -0700
From: Dave Jiang <dave.jiang@...el.com>
To: yuanli fu <fuyuanli0722@...il.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.



On 9/2/25 7:20 PM, yuanli fu wrote:
> 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?

Jon will merge it when he has a chance.

> 
> 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) {
>>