From: Shuah Khan <skhan@linuxfoundation.org>
To: Kalle Valo <kvalo@codeaurora.org>
Cc: netdev@vger.kernel.org, linux-wireless@vger.kernel.org,
linux-kernel@vger.kernel.org, ath10k@lists.infradead.org,
Shuah Khan <skhan@linuxfoundation.org>,
kuba@kernel.org, davem@davemloft.net
Subject: Re: [PATCH 4/5] ath10k: detect conf_mutex held ath10k_drain_tx() calls
Date: Wed, 10 Feb 2021 08:57:04 -0700 [thread overview]
Message-ID: <d6d8c7b8-f69d-01ef-6d66-8a33ea98920f@linuxfoundation.org> (raw)
In-Reply-To: <87lfbwtjls.fsf@codeaurora.org>
On 2/10/21 1:25 AM, Kalle Valo wrote:
> Shuah Khan <skhan@linuxfoundation.org> 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 <skhan@linuxfoundation.org>
>
> 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
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next prev parent reply other threads:[~2021-02-10 15:57 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-10 0:42 [PATCH 0/5] ath10k fixes for warns Shuah Khan
2021-02-10 0:42 ` [PATCH 1/5] ath10k: fix conf_mutex lock assert in ath10k_debug_fw_stats_request() Shuah Khan
2021-02-10 8:09 ` Kalle Valo
[not found] ` <20210210080915.8A81AC433C6@smtp.codeaurora.org>
2021-02-10 16:21 ` Shuah Khan
2021-02-10 0:42 ` [PATCH 2/5] ath10k: fix WARNING: suspicious RCU usage Shuah Khan
2021-02-10 8:13 ` Kalle Valo
[not found] ` <20210210081320.2FBE5C433CA@smtp.codeaurora.org>
2021-02-10 16:22 ` Shuah Khan
2021-02-10 0:42 ` [PATCH 3/5] ath10k: change ath10k_offchan_tx_work() peer present msg to a warn Shuah Khan
2021-02-11 6:50 ` Kalle Valo
2021-02-10 0:42 ` [PATCH 4/5] ath10k: detect conf_mutex held ath10k_drain_tx() calls Shuah Khan
2021-02-10 8:03 ` kernel test robot
2021-02-10 8:25 ` Kalle Valo
2021-02-10 15:57 ` Shuah Khan [this message]
2021-02-11 11:20 ` Kalle Valo
2021-02-11 20:53 ` Shuah Khan
2021-02-11 0:13 ` kernel test robot
2021-02-10 0:42 ` [PATCH 5/5] ath10k: reduce invalid ht params rate message noise Shuah Khan
2021-02-10 2:36 ` Wen Gong
2021-02-10 8:28 ` Kalle Valo
2021-02-10 16:13 ` Shuah Khan
2021-02-11 11:24 ` Kalle Valo
2021-02-26 18:01 ` Shuah Khan
2023-09-20 18:27 ` James Prestwood
2023-09-20 19:23 ` Jeff Johnson
2023-11-14 19:31 ` James Prestwood
2023-11-14 20:57 ` Jeff Johnson
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