linux-kernel - Re: [PATCH v3 2/3] staging: mt7621-mmc: Initialize completions a single time during probe

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Message-ID: <20190322141949.GA23722@kroah.com>
Date:   Fri, 22 Mar 2019 15:19:49 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     George Hilliard <thirtythreeforty@...il.com>
Cc:     linux-mips@...ux-mips.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/3] staging: mt7621-mmc: Initialize completions a
 single time during probe

On Wed, Mar 20, 2019 at 04:42:04PM -0600, George Hilliard wrote:
> The module was initializing completions whenever it was going to wait on
> them, and not when the completion was allocated.  This is incorrect
> according to the completion docs:
> 
>     Calling init_completion() on the same completion object twice is
>     most likely a bug [...]
> 
> Re-initialization is also unnecessary because the module never uses
> complete_all().  Fix this by only ever initializing the completion a
> single time, and log if the completions are not consumed as intended
> (this is not a fatal problem, but should not go unnoticed).
> 
> Signed-off-by: George Hilliard <thirtythreeforty@...il.com>
> ---
> v2: Rebased v1
> v3: Removed BUG_ON() calls, and politely log; this failure won't kill us
> 
>  drivers/staging/mt7621-mmc/sd.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/staging/mt7621-mmc/sd.c b/drivers/staging/mt7621-mmc/sd.c
> index ff01872ab972..139533606863 100644
> --- a/drivers/staging/mt7621-mmc/sd.c
> +++ b/drivers/staging/mt7621-mmc/sd.c
> @@ -466,7 +466,10 @@ static unsigned int msdc_command_start(struct msdc_host   *host,
>  	host->cmd     = cmd;
>  	host->cmd_rsp = resp;
>  
> -	init_completion(&host->cmd_done);
> +	// The completion should have been consumed by the previous command
> +	// response handler, because the mmc requests should be serialized
> +	if(completion_done(&host->cmd_done))
> +		dev_err(mmc_dev(host->mmc), "previous command was not handled\n");

Proper coding style please :(