Re: [PATCH] mtd: spi-nor: scope the exclusive RWW lock

[Michael Walle]

On Sun Aug 9, 2026 at 10:42 AM CEST, Runyu Xiao wrote:
> spi_nor_rww_start_exclusive() is used as a wait_event_killable()
> condition. The raw mutex_lock() leaves nor->lock held when the busy
> condition returns false, so the waiter can block the active operation that
> must clear the RWW state.
>
> Use the same scoped mutex guard as the other RWW start helpers so the
> mutex is released on both the busy and successful condition paths. The
> state flags remain the handoff to the caller, while
> spi_nor_rww_end_exclusive() continues
> to acquire the mutex when clearing them.
>
> The change was checked by comparing the original and patched source.

What do you mean? Was this AI assisted?

> A source-level check of the original wait condition found that it takes
> `nor->lock` and returns false while an RWW operation is still active. The
> patched source was checked for a scoped mutex guard that releases
> `nor->lock` before the wait condition returns. A user-space pthread model
> held `nor->lock` on the false-condition path and showed that the
> operation-ending path then blocks when it needs the same mutex. No live
> SPI-NOR test was run.

What do you mean by "user-space pthread model"? Ported this into
user-space and tried it there? Please keep the commit message
precise and don't use any AI gibberish. Please, explain what's going
on with your own sentences. That way, it shows at least some
understanding what you are trying to change here.

That being said, there is something odd about that commit. Tudor, do
you know why you've omitted the guard() in spi_nor_rww_start_exclusive()?

-michael

> Fixes: 03e7bb864d9a ("mtd: spi-nor: use scope-based mutex cleanup helpers")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Runyu Xiao <runyu.xiao@xxxxxxxxxx>
> ---
>  drivers/mtd/spi-nor/core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
> index ccf4396cdcd0..8bc117b46e02 100644
> --- a/drivers/mtd/spi-nor/core.c
> +++ b/drivers/mtd/spi-nor/core.c
> @@ -1310,7 +1310,7 @@ static bool spi_nor_rww_start_exclusive(struct spi_nor *nor)
>  {
>  	struct spi_nor_rww *rww = &nor->rww;
>  
> -	mutex_lock(&nor->lock);
> +	guard(mutex)(&nor->lock);
>  
>  	if (rww->ongoing_io || rww->ongoing_rd || rww->ongoing_pe)
>  		return false;

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