Re: [PATCH v2 06/11] staging: mt7621-mmc: Initialize completions a single time during probe

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Mon, Mar 18, 2019 at 08:20:07PM -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.
> 
> Signed-off-by: George Hilliard <thirtythreeforty@gmail.com>
> ---
>  drivers/staging/mt7621-mmc/sd.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/staging/mt7621-mmc/sd.c b/drivers/staging/mt7621-mmc/sd.c
> index 89fbc0a1dec7..c272aa780719 100644
> --- a/drivers/staging/mt7621-mmc/sd.c
> +++ b/drivers/staging/mt7621-mmc/sd.c
> @@ -467,7 +467,9 @@ 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
> +	BUG_ON(completion_done(&host->cmd_done));

Adding new BUG_ON() calls is not ok.  That crashes the machine and will
break everyone.  If this really is a potential error that could happen,
then handle it.  If not, then do not even put this there, it's not
needed.

All of the BUG_ON() entries need to be removed in the end from this code
anyway.

thanks,

greg k-h