linux-kernel - Re: [PATCH 1/2] fsi: core: Lock scan mutex for master index removal

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Date:   Wed, 31 May 2023 07:47:54 +0000
From:   Joel Stanley <joel@....id.au>
To:     Eddie James <eajames@...ux.ibm.com>
Cc:     linux-fsi@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        jk@...abs.org, alistair@...ple.id.au
Subject: Re: [PATCH 1/2] fsi: core: Lock scan mutex for master index removal

On Wed, 12 Apr 2023 at 18:56, Eddie James <eajames@...ux.ibm.com> wrote:
>
> If a master scan occurs while the master is being unregistered,
> the devicecs may end up with incorrect and possibly duplicate names,

typo: devices

> resulting in kernel warnings. Ensure the master index isn't changed
> outside of the scan mutex.
>
> Signed-off-by: Eddie James <eajames@...ux.ibm.com>
> ---
>  drivers/fsi/fsi-core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/fsi/fsi-core.c b/drivers/fsi/fsi-core.c
> index fcbf0469ce3f..18d4d68482d7 100644
> --- a/drivers/fsi/fsi-core.c
> +++ b/drivers/fsi/fsi-core.c
> @@ -1354,12 +1354,12 @@ EXPORT_SYMBOL_GPL(fsi_master_register);
>
>  void fsi_master_unregister(struct fsi_master *master)
>  {
> +       mutex_lock(&master->scan_lock);

The ida functions are supposed to not require locking, but protecting
against the test and changing of ->idx makes sense.

Do you want to add a Fixes: line?

>         if (master->idx >= 0) {
>                 ida_simple_remove(&master_ida, master->idx);

the ida_simple functions are depreciated, at some point we should
replace them with ida_alloc/ida_free.

>                 master->idx = -1;
>         }
>
> -       mutex_lock(&master->scan_lock);
>         fsi_master_unscan(master);
>         mutex_unlock(&master->scan_lock);
>         device_unregister(&master->dev);
> --
> 2.31.1
>