Shuah Khan <[email protected]> writes:
> ath10k_drain_tx() must not be called with conf_mutex held as workers can
> use that also. Add check to detect conf_mutex held calls.
>
> Signed-off-by: Shuah Khan <[email protected]>
The commit log does not answer to "Why?". How did you find this? What
actual problem are you trying to solve?
> ---
> drivers/net/wireless/ath/ath10k/mac.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/drivers/net/wireless/ath/ath10k/mac.c b/drivers/net/wireless/ath/ath10k/mac.c
> index 53f92945006f..3545ce7dce0a 100644
> --- a/drivers/net/wireless/ath/ath10k/mac.c
> +++ b/drivers/net/wireless/ath/ath10k/mac.c
> @@ -4566,6 +4566,7 @@ static void ath10k_mac_op_wake_tx_queue(struct ieee80211_hw *hw,
> /* Must not be called with conf_mutex held as workers can use that also. */
> void ath10k_drain_tx(struct ath10k *ar)
> {
> + WARN_ON(lockdep_is_held(&ar->conf_mutex));
Empty line after WARN_ON().
Shouldn't this check debug_locks similarly lockdep_assert_held() does?
#define lockdep_assert_held(l) do { \
WARN_ON(debug_locks && !lockdep_is_held(l)); \
} while (0)
And I suspect you need #ifdef CONFIG_LOCKDEP which should fix the kbuild
bot error.
But honestly I would prefer to have lockdep_assert_not_held() in
include/linux/lockdep.h, much cleaner that way. Also
i915_gem_object_lookup_rcu() could then use the same macro.
--
https://patchwork.kernel.org/project/linux-wireless/list/
https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches
On 2/10/21 1:25 AM, Kalle Valo wrote:
> Shuah Khan <[email protected]> writes:
>
>> ath10k_drain_tx() must not be called with conf_mutex held as workers can
>> use that also. Add check to detect conf_mutex held calls.
>>
>> Signed-off-by: Shuah Khan <[email protected]>
>
> The commit log does not answer to "Why?". How did you find this? What
> actual problem are you trying to solve?
>
I came across the comment block above the ath10k_drain_tx() as I was
reviewing at conf_mutex holds while I was debugging the conf_mutex
lock assert in ath10k_debug_fw_stats_request().
My reasoning is that having this will help detect incorrect usages
of ath10k_drain_tx() while holding conf_mutex which could lead to
locking problems when async worker routines try to call this routine.
>> ---
>> drivers/net/wireless/ath/ath10k/mac.c | 1 +
>> 1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/net/wireless/ath/ath10k/mac.c b/drivers/net/wireless/ath/ath10k/mac.c
>> index 53f92945006f..3545ce7dce0a 100644
>> --- a/drivers/net/wireless/ath/ath10k/mac.c
>> +++ b/drivers/net/wireless/ath/ath10k/mac.c
>> @@ -4566,6 +4566,7 @@ static void ath10k_mac_op_wake_tx_queue(struct ieee80211_hw *hw,
>> /* Must not be called with conf_mutex held as workers can use that also. */
>> void ath10k_drain_tx(struct ath10k *ar)
>> {
>> + WARN_ON(lockdep_is_held(&ar->conf_mutex));
>
> Empty line after WARN_ON().
>
Will do.
> Shouldn't this check debug_locks similarly lockdep_assert_held() does?
>
> #define lockdep_assert_held(l) do { \
> WARN_ON(debug_locks && !lockdep_is_held(l)); \
> } while (0)
>
> And I suspect you need #ifdef CONFIG_LOCKDEP which should fix the kbuild
> bot error.
>
Yes.
> But honestly I would prefer to have lockdep_assert_not_held() in
> include/linux/lockdep.h, much cleaner that way. Also
> i915_gem_object_lookup_rcu() could then use the same macro.
>
Right. This is the right way to go. That was first instinct and
decided to have the discussion evolve in that direction. Now that
it has, I will combine this change with
include/linux/lockdep.h and add lockdep_assert_not_held()
I think we might have other places in the kernel that could use
lockdep_assert_not_held() in addition to i915_gem_object_lookup_rcu()
thanks,
-- Shuah