netdev - Re: [PATCH] SUNRPC: Set tk_rpc_status when RPC_TASK

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Message-ID: <58bf9d83-b58d-e5a6-4096-64eb96f3854a@huawei.com>
Date: Fri, 17 Jan 2025 10:29:31 +0800
From: yangerkun <yangerkun@...wei.com>
To: Trond Myklebust <trondmy@...merspace.com>, "horms@...nel.org"
	<horms@...nel.org>, "davem@...emloft.net" <davem@...emloft.net>,
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	"anna@...nel.org" <anna@...nel.org>, "lilingfeng3@...wei.com"
	<lilingfeng3@...wei.com>, "Dai.Ngo@...cle.com" <Dai.Ngo@...cle.com>,
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CC: "lilingfeng@...weicloud.com" <lilingfeng@...weicloud.com>,
	"houtao1@...wei.com" <houtao1@...wei.com>, "linux-nfs@...r.kernel.org"
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	<yukuai1@...weicloud.com>, "yi.zhang@...wei.com" <yi.zhang@...wei.com>
Subject: Re: [PATCH] SUNRPC: Set tk_rpc_status when RPC_TASK_SIGNALLED is
 detected



在 2025/1/17 4:52, Trond Myklebust 写道:
> On Thu, 2025-01-16 at 19:43 +0800, yangerkun wrote:
>> Hi,
>>
>> Thanks for the patch.
>>
>> Before 39494194f93b("SUNRPC: Fix races with rpc_killall_tasks()",
>> every
>> time we set RPC_TASK_SIGNALLED, when we go through __rpc_execute,
>> this
>> rpc_task will immediate break and exist.
>>
>> However after that, __rpc_execute won't judge RPC_TASK_SIGNNALED, so
>> for
>> the case like you point out below, even after your commit
>> rpc_check_timeout will help break and exist eventually, but this
>> rpc_task has already do some work. I prefer reintroduce judging
>> RPC_TASK_SIGNNALED in __rpc_execute to help exist immediatly.
>>
> 
> Better yet... Let's get rid of the RPC_TASK_SIGNALLED flag altogether
> and just replace
> 
> #define RPC_TASK_SIGNALLED(task) (READ_ONCE(task->tk_rpc_status) == -ERESTARTSYS)

Hi,

Thanks for your reply! Yeah, if all the places where tk_rpc_status is
updated are by calling rpc_task_set_rpc_status, we can use
task->tk_rpc_status == -ERESTARTSYS to determine whether rpc_task is
RPC_TASK_SIGNALLED. But for the case like Li has provided,
__rpc_restart_call won't do this, and will overwrite tk_rpc_status 
unconditionally. This won't be a stable solution. Maybe it's better to
change __rpc_restart_call calling rpc_task_set_rpc_status too? And
__rpc_execute will be enough to help solve this case.

> 
> There is no good reason to try to maintain two completely separate
> sources of truth to describe the same task state.
>