linux-kernel - Re: [PATCH] binder: fixed coverity warning by moving pr

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Date:   Sat, 4 Dec 2021 08:57:17 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Ameer Hamza <amhamza.mgc@...il.com>
Cc:     arve@...roid.com, tkjos@...roid.com, maco@...roid.com,
        joel@...lfernandes.org, christian@...uner.io, hridya@...gle.com,
        surenb@...gle.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] binder: fixed coverity warning by moving pr_warn outside
 lock

On Sat, Dec 04, 2021 at 01:50:41AM +0500, Ameer Hamza wrote:
> Coverity warns about using print operations within a lock due to
> unlikely possible deadlock scenario, however, this warning can be
> easily avoided here without having any effect on the program flow.
> 
> Addresses-Coverity: 1494148 ("Thread deadlock")

Sounds like coverity is wrong, you can print any time, locks do not
matter here.

Do you have a link to the exact coverity report for this?

> Signed-off-by: Ameer Hamza <amhamza.mgc@...il.com>
> ---
>  drivers/android/binder.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/android/binder.c b/drivers/android/binder.c
> index cffbe57a8e08..8ee942eef51d 100644
> --- a/drivers/android/binder.c
> +++ b/drivers/android/binder.c
> @@ -1507,14 +1507,14 @@ static void binder_free_transaction(struct binder_transaction *t)
>  	if (target_proc) {
>  		binder_inner_proc_lock(target_proc);
>  		target_proc->outstanding_txns--;
> -		if (target_proc->outstanding_txns < 0)
> -			pr_warn("%s: Unexpected outstanding_txns %d\n",
> -				__func__, target_proc->outstanding_txns);
>  		if (!target_proc->outstanding_txns && target_proc->is_frozen)
>  			wake_up_interruptible_all(&target_proc->freeze_wait);
>  		if (t->buffer)
>  			t->buffer->transaction = NULL;
>  		binder_inner_proc_unlock(target_proc);
> +		if (target_proc->outstanding_txns < 0)
> +			pr_warn("%s: Unexpected outstanding_txns %d\n",
> +				__func__, target_proc->outstanding_txns);

Have you seen problems with the location of the existing message?  If
not, this should be fine.

thanks,

greg k-h