linux-kernel - Re: [PATCH] drivers: firewire: core-transaction: Pass lockdep condition to address_handler

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Date:   Sat, 4 Jan 2020 16:21:31 -0500
From:   Joel Fernandes <joel@...lfernandes.org>
To:     madhuparnabhowmik04@...il.com
Cc:     stefanr@...6.in-berlin.de, paulmck@...nel.org,
        linux1394-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, rcu@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org, frextrite@...il.com
Subject: Re: [PATCH] drivers: firewire: core-transaction: Pass lockdep
 condition to address_handler_list iterator

On Sat, Jan 04, 2020 at 08:12:15PM +0530, madhuparnabhowmik04@...il.com wrote:
> From: Madhuparna Bhowmik <madhuparnabhowmik04@...il.com>
> 
> The address_handler_list is traversed with list_for_each_entry_rcu
> with address_handler_list_lock held.
> list_for_each_entry_rcu has built-in RCU and lock checking.
> Use it for address_handler_list traversal.
> 
> Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik04@...il.com>

Reviewed-by: Joel Fernandes (Google) <joel@...lfernandes.org>

thanks,

 - Joel

> ---
>  drivers/firewire/core-transaction.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/firewire/core-transaction.c b/drivers/firewire/core-transaction.c
> index 404a035f104d..a15e70027932 100644
> --- a/drivers/firewire/core-transaction.c
> +++ b/drivers/firewire/core-transaction.c
> @@ -61,6 +61,11 @@
>  #define PHY_CONFIG_ROOT_ID(node_id)	((((node_id) & 0x3f) << 24) | (1 << 23))
>  #define PHY_IDENTIFIER(id)		((id) << 30)
>  
> +static DEFINE_SPINLOCK(address_handler_list_lock);
> +static LIST_HEAD(address_handler_list);
> +
> +#define address_handler_list_lock_held() lock_is_held(&(address_handler_list_lock).dep_map)
> +
>  /* returns 0 if the split timeout handler is already running */
>  static int try_cancel_split_timeout(struct fw_transaction *t)
>  {
> @@ -485,7 +490,7 @@ static struct fw_address_handler *lookup_overlapping_address_handler(
>  {
>  	struct fw_address_handler *handler;
>  
> -	list_for_each_entry_rcu(handler, list, link) {
> +	list_for_each_entry_rcu(handler, list, link, address_handler_list_lock_held()) {
>  		if (handler->offset < offset + length &&
>  		    offset < handler->offset + handler->length)
>  			return handler;
> @@ -514,8 +519,6 @@ static struct fw_address_handler *lookup_enclosing_address_handler(
>  	return NULL;
>  }
>  
> -static DEFINE_SPINLOCK(address_handler_list_lock);
> -static LIST_HEAD(address_handler_list);
>  
>  const struct fw_address_region fw_high_memory_region =
>  	{ .start = FW_MAX_PHYSICAL_RANGE, .end = 0xffffe0000000ULL, };
> -- 
> 2.17.1
>