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Sender: Corey Minyard <tcminyard@gmail.com>
Date:   Wed, 12 Apr 2023 07:34:49 -0500
From:   Corey Minyard <minyard@acm.org>
To:     Zhang Yuchen <zhangyuchen.lcr@bytedance.com>
Cc:     openipmi-developer@lists.sourceforge.net,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] ipmi: fix SSIF not responding under certain cond.
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Reply-To: minyard@acm.org
References: <20230412074907.80046-1-zhangyuchen.lcr@bytedance.com>
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On Wed, Apr 12, 2023 at 03:49:07PM +0800, Zhang Yuchen wrote:
> The ipmi communication is not restored after a specific version of BMC is
> upgraded on our server.
> The ipmi driver does not respond after printing the following log:

Excellent explaination, this is queued in my branch for the next release
and marked for backport.

Thank you,

-corey

> 
>     ipmi_ssif: Invalid response getting flags: 1c 1
> 
> I found that after entering this branch, ssif_info->ssif_state always
> holds SSIF_GETTING_FLAGS and never return to IDLE.
> 
> As a result, the driver cannot be loaded, because the driver status is
> checked during the unload process and must be IDLE in shutdown_ssif():
> 
>         while (ssif_info->ssif_state != SSIF_IDLE)
>                 schedule_timeout(1);
> 
> The process trigger this problem is:
> 
> 1. One msg timeout and next msg start send, and call
> ssif_set_need_watch().
> 
> 2. ssif_set_need_watch()->watch_timeout()->start_flag_fetch() change
> ssif_state to SSIF_GETTING_FLAGS.
> 
> 3. In msg_done_handler() ssif_state == SSIF_GETTING_FLAGS, if an error
> message is received, the second branch does not modify the ssif_state.
> 
> 4. All retry action need IS_SSIF_IDLE() == True. Include retry action in
> watch_timeout(), msg_done_handler(). Sending msg does not work either.
> SSIF_IDLE is also checked in start_next_msg().
> 
> 5. The only thing that can be triggered in the SSIF driver is
> watch_timeout(), after destory_user(), this timer will stop too.
> 
> So, if enter this branch, the ssif_state will remain SSIF_GETTING_FLAGS
> and can't send msg, no timer started, can't unload.
> 
> We did a comparative test before and after adding this patch, and the
> result is effective.
> 
> Fixes: 259307074bfc ("ipmi: Add SMBus interface driver (SSIF)")
> 
> Signed-off-by: Zhang Yuchen <zhangyuchen.lcr@bytedance.com>
> ---
>  drivers/char/ipmi/ipmi_ssif.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/char/ipmi/ipmi_ssif.c b/drivers/char/ipmi/ipmi_ssif.c
> index a5ddebb1edea..48be3694fa64 100644
> --- a/drivers/char/ipmi/ipmi_ssif.c
> +++ b/drivers/char/ipmi/ipmi_ssif.c
> @@ -784,9 +784,9 @@ static void msg_done_handler(struct ssif_info *ssif_info, int result,
>  		} else if (data[0] != (IPMI_NETFN_APP_REQUEST | 1) << 2
>  			   || data[1] != IPMI_GET_MSG_FLAGS_CMD) {
>  			/*
> -			 * Don't abort here, maybe it was a queued
> -			 * response to a previous command.
> +			 * Recv error response, give up.
>  			 */
> +			ssif_info->ssif_state = SSIF_IDLE;
>  			ipmi_ssif_unlock_cond(ssif_info, flags);
>  			dev_warn(&ssif_info->client->dev,
>  				 "Invalid response getting flags: %x %x\n",
> -- 
> 2.20.1
>