* [PATCH 0/2] Add lockdep_assert_not_held()
@ 2021-02-12 23:28 Shuah Khan
2021-02-12 23:28 ` [PATCH 1/2] lockdep: add lockdep_assert_not_held() Shuah Khan
2021-02-12 23:28 ` [PATCH 2/2] ath10k: detect conf_mutex held ath10k_drain_tx() calls Shuah Khan
0 siblings, 2 replies; 10+ messages in thread
From: Shuah Khan @ 2021-02-12 23:28 UTC (permalink / raw)
To: peterz, mingo, will, kvalo, davem, kuba
Cc: Shuah Khan, ath10k, linux-wireless, netdev, linux-kernel
Some kernel functions must not be called holding a specific lock. Doing
so could lead to locking problems. Currently these routines call
lock_is_held() to check for lock hold followed by WARN_ON.
Adding a common lockdep interface will help reduce the duplication of this
logic in the rest of the kernel.
Add lockdep_assert_not_held() to be used in these functions to detect
incorrect calls while holding a lock.
lockdep_assert_not_held() provides the opposite functionality of
lockdep_assert_held() which is used to assert calls that require
holding a specific lock.
The need for lockdep_assert_not_held() came up in a discussion on
ath10k patch. ath10k_drain_tx() and i915_vma_pin_ww() are examples
of functions that can use lockdep_assert_not_held().
Link: https://lore.kernel.org/linux-wireless/871rdmu9z9.fsf@codeaurora.org/
This patch series adds lockdep_assert_not_held() and uses it in the
second patch in ath10k_drain_tx() function.
Shuah Khan (2):
lockdep: add lockdep_assert_not_held()
ath10k: detect conf_mutex held ath10k_drain_tx() calls
drivers/net/wireless/ath/ath10k/mac.c | 2 ++
include/linux/lockdep.h | 7 ++++++-
2 files changed, 8 insertions(+), 1 deletion(-)
--
2.27.0
^ permalink raw reply [flat|nested] 10+ messages in thread
* [PATCH 1/2] lockdep: add lockdep_assert_not_held()
2021-02-12 23:28 [PATCH 0/2] Add lockdep_assert_not_held() Shuah Khan
@ 2021-02-12 23:28 ` Shuah Khan
2021-02-14 17:53 ` Peter Zijlstra
2021-02-12 23:28 ` [PATCH 2/2] ath10k: detect conf_mutex held ath10k_drain_tx() calls Shuah Khan
1 sibling, 1 reply; 10+ messages in thread
From: Shuah Khan @ 2021-02-12 23:28 UTC (permalink / raw)
To: peterz, mingo, will, kvalo, davem, kuba
Cc: Shuah Khan, ath10k, linux-wireless, netdev, linux-kernel
Some kernel functions must not be called holding a specific lock. Doing
so could lead to locking problems. Currently these routines call
lock_is_held() to check for lock hold followed by WARN_ON.
Adding a common lockdep interface will help reduce the duplication of this
logic in the rest of the kernel.
Add lockdep_assert_not_held() to be used in these functions to detect
incorrect calls while holding a lock.
lockdep_assert_not_held() provides the opposite functionality of
lockdep_assert_held() which is used to assert calls that require
holding a specific lock.
The need for lockdep_assert_not_held() came up in a discussion on
ath10k patch. ath10k_drain_tx() and i915_vma_pin_ww() are examples
of functions that can use lockdep_assert_not_held().
Link: https://lore.kernel.org/linux-wireless/871rdmu9z9.fsf@codeaurora.org/
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
---
include/linux/lockdep.h | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index b9e9adec73e8..567e3a1a27ce 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -294,6 +294,10 @@ extern void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie);
#define lockdep_depth(tsk) (debug_locks ? (tsk)->lockdep_depth : 0)
+#define lockdep_assert_not_held(l) do { \
+ WARN_ON(debug_locks && lockdep_is_held(l)); \
+ } while (0)
+
#define lockdep_assert_held(l) do { \
WARN_ON(debug_locks && !lockdep_is_held(l)); \
} while (0)
@@ -383,8 +387,9 @@ extern int lock_is_held(const void *);
extern int lockdep_is_held(const void *);
#define lockdep_is_held_type(l, r) (1)
+#define lockdep_assert_not_held(l) do { (void)(l); } while (0)
#define lockdep_assert_held(l) do { (void)(l); } while (0)
-#define lockdep_assert_held_write(l) do { (void)(l); } while (0)
+#define lockdep_assert_held_write(l) do { (void)(l); } while (0)
#define lockdep_assert_held_read(l) do { (void)(l); } while (0)
#define lockdep_assert_held_once(l) do { (void)(l); } while (0)
--
2.27.0
^ permalink raw reply related [flat|nested] 10+ messages in thread
* [PATCH 2/2] ath10k: detect conf_mutex held ath10k_drain_tx() calls
2021-02-12 23:28 [PATCH 0/2] Add lockdep_assert_not_held() Shuah Khan
2021-02-12 23:28 ` [PATCH 1/2] lockdep: add lockdep_assert_not_held() Shuah Khan
@ 2021-02-12 23:28 ` Shuah Khan
2021-02-14 6:08 ` Kalle Valo
1 sibling, 1 reply; 10+ messages in thread
From: Shuah Khan @ 2021-02-12 23:28 UTC (permalink / raw)
To: peterz, mingo, will, kvalo, davem, kuba
Cc: Shuah Khan, ath10k, linux-wireless, netdev, linux-kernel
ath10k_drain_tx() must not be called with conf_mutex held as workers can
use that also. Add call to lockdep_assert_not_held() on conf_mutex to
detect if conf_mutex is held by the caller.
The idea for this patch stemmed from coming across the comment block
above the ath10k_drain_tx() while reviewing the conf_mutex holds during
to debug the conf_mutex lock assert in ath10k_debug_fw_stats_request().
Adding detection to assert on conf_mutex hold will help detect incorrect
usages that could lead to locking problems when async worker routines try
to call this routine.
Link: https://lore.kernel.org/linux-wireless/871rdmu9z9.fsf@codeaurora.org/
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
---
drivers/net/wireless/ath/ath10k/mac.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/net/wireless/ath/ath10k/mac.c b/drivers/net/wireless/ath/ath10k/mac.c
index c202b167d8c6..7de05b679ad2 100644
--- a/drivers/net/wireless/ath/ath10k/mac.c
+++ b/drivers/net/wireless/ath/ath10k/mac.c
@@ -4728,6 +4728,8 @@ 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)
{
+ lockdep_assert_not_held(&ar->conf_mutex);
+
/* make sure rcu-protected mac80211 tx path itself is drained */
synchronize_net();
--
2.27.0
^ permalink raw reply related [flat|nested] 10+ messages in thread
* Re: [PATCH 2/2] ath10k: detect conf_mutex held ath10k_drain_tx() calls
2021-02-12 23:28 ` [PATCH 2/2] ath10k: detect conf_mutex held ath10k_drain_tx() calls Shuah Khan
@ 2021-02-14 6:08 ` Kalle Valo
0 siblings, 0 replies; 10+ messages in thread
From: Kalle Valo @ 2021-02-14 6:08 UTC (permalink / raw)
To: Shuah Khan
Cc: peterz, mingo, will, davem, kuba, ath10k, linux-wireless, netdev,
linux-kernel
Shuah Khan <skhan@linuxfoundation.org> writes:
> ath10k_drain_tx() must not be called with conf_mutex held as workers can
> use that also. Add call to lockdep_assert_not_held() on conf_mutex to
> detect if conf_mutex is held by the caller.
>
> The idea for this patch stemmed from coming across the comment block
> above the ath10k_drain_tx() while reviewing the conf_mutex holds during
> to debug the conf_mutex lock assert in ath10k_debug_fw_stats_request().
>
> Adding detection to assert on conf_mutex hold will help detect incorrect
> usages that could lead to locking problems when async worker routines try
> to call this routine.
>
> Link: https://lore.kernel.org/linux-wireless/871rdmu9z9.fsf@codeaurora.org/
> Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
This can go via the same tree as patch 1:
Acked-by: Kalle Valo <kvalo@codeaurora.org>
But I can also take this to my ath tree, once patch 1 has reached it.
Just let me know what is preferred.
--
https://patchwork.kernel.org/project/linux-wireless/list/
https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH 1/2] lockdep: add lockdep_assert_not_held()
2021-02-12 23:28 ` [PATCH 1/2] lockdep: add lockdep_assert_not_held() Shuah Khan
@ 2021-02-14 17:53 ` Peter Zijlstra
2021-02-15 10:44 ` Peter Zijlstra
0 siblings, 1 reply; 10+ messages in thread
From: Peter Zijlstra @ 2021-02-14 17:53 UTC (permalink / raw)
To: Shuah Khan
Cc: mingo, will, kvalo, davem, kuba, ath10k, linux-wireless, netdev,
linux-kernel
On Fri, Feb 12, 2021 at 04:28:42PM -0700, Shuah Khan wrote:
> +#define lockdep_assert_not_held(l) do { \
> + WARN_ON(debug_locks && lockdep_is_held(l)); \
> + } while (0)
> +
This thing isn't as straight forward as you might think, but it'll
mostly work.
Notably this thing will misfire when lockdep_off() is employed. It
certainyl needs a comment to explain the subtleties.
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH 1/2] lockdep: add lockdep_assert_not_held()
2021-02-14 17:53 ` Peter Zijlstra
@ 2021-02-15 10:44 ` Peter Zijlstra
2021-02-15 13:12 ` Johannes Berg
0 siblings, 1 reply; 10+ messages in thread
From: Peter Zijlstra @ 2021-02-15 10:44 UTC (permalink / raw)
To: Shuah Khan
Cc: mingo, will, kvalo, davem, kuba, ath10k, linux-wireless, netdev,
linux-kernel
On Sun, Feb 14, 2021 at 06:53:01PM +0100, Peter Zijlstra wrote:
> On Fri, Feb 12, 2021 at 04:28:42PM -0700, Shuah Khan wrote:
>
> > +#define lockdep_assert_not_held(l) do { \
> > + WARN_ON(debug_locks && lockdep_is_held(l)); \
> > + } while (0)
> > +
>
> This thing isn't as straight forward as you might think, but it'll
> mostly work.
>
> Notably this thing will misfire when lockdep_off() is employed. It
> certainyl needs a comment to explain the subtleties.
I think something like so will work, but please double check.
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index b9e9adec73e8..c8b0d292bf8e 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -294,11 +294,15 @@ extern void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie);
#define lockdep_depth(tsk) (debug_locks ? (tsk)->lockdep_depth : 0)
-#define lockdep_assert_held(l) do { \
- WARN_ON(debug_locks && !lockdep_is_held(l)); \
+#define lockdep_assert_held(l) do { \
+ WARN_ON(debug_locks && lockdep_is_held(l) == 0)); \
} while (0)
-#define lockdep_assert_held_write(l) do { \
+#define lockdep_assert_not_held(l) do { \
+ WARN_ON(debug_locks && lockdep_is_held(l) == 1)); \
+ } while (0)
+
+#define lockdep_assert_held_write(l) do { \
WARN_ON(debug_locks && !lockdep_is_held_type(l, 0)); \
} while (0)
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index c1418b47f625..983ba206f7b2 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -5467,7 +5467,7 @@ noinstr int lock_is_held_type(const struct lockdep_map *lock, int read)
int ret = 0;
if (unlikely(!lockdep_enabled()))
- return 1; /* avoid false negative lockdep_assert_held() */
+ return -1; /* avoid false negative lockdep_assert_held() */
raw_local_irq_save(flags);
check_flags(flags);
^ permalink raw reply related [flat|nested] 10+ messages in thread
* Re: [PATCH 1/2] lockdep: add lockdep_assert_not_held()
2021-02-15 10:44 ` Peter Zijlstra
@ 2021-02-15 13:12 ` Johannes Berg
2021-02-15 16:04 ` Peter Zijlstra
0 siblings, 1 reply; 10+ messages in thread
From: Johannes Berg @ 2021-02-15 13:12 UTC (permalink / raw)
To: Peter Zijlstra, Shuah Khan
Cc: mingo, will, kvalo, davem, kuba, ath10k, linux-wireless, netdev,
linux-kernel
On Mon, 2021-02-15 at 11:44 +0100, Peter Zijlstra wrote:
>
> I think something like so will work, but please double check.
Yeah, that looks better.
> +++ b/include/linux/lockdep.h
> @@ -294,11 +294,15 @@ extern void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie);
>
> #define lockdep_depth(tsk) (debug_locks ? (tsk)->lockdep_depth : 0)
>
> -#define lockdep_assert_held(l) do { \
> - WARN_ON(debug_locks && !lockdep_is_held(l)); \
> +#define lockdep_assert_held(l) do { \
> + WARN_ON(debug_locks && lockdep_is_held(l) == 0)); \
> } while (0)
That doesn't really need to change? It's the same.
> -#define lockdep_assert_held_write(l) do { \
> +#define lockdep_assert_not_held(l) do { \
> + WARN_ON(debug_locks && lockdep_is_held(l) == 1)); \
> + } while (0)
> +
> +#define lockdep_assert_held_write(l) do { \
> WARN_ON(debug_locks && !lockdep_is_held_type(l, 0)); \
> } while (0)
>
> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> index c1418b47f625..983ba206f7b2 100644
> --- a/kernel/locking/lockdep.
> +++ b/kernel/locking/lockdep.c
> @@ -5467,7 +5467,7 @@ noinstr int lock_is_held_type(const struct lockdep_map *lock, int read)
> int ret = 0;
>
> if (unlikely(!lockdep_enabled()))
> - return 1; /* avoid false negative lockdep_assert_held() */
> + return -1; /* avoid false negative lockdep_assert_held() */
Maybe add lockdep_assert_not_held() to the comment, to explain the -1
(vs non-zero)?
johannes
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH 1/2] lockdep: add lockdep_assert_not_held()
2021-02-15 13:12 ` Johannes Berg
@ 2021-02-15 16:04 ` Peter Zijlstra
2021-02-15 16:10 ` Johannes Berg
0 siblings, 1 reply; 10+ messages in thread
From: Peter Zijlstra @ 2021-02-15 16:04 UTC (permalink / raw)
To: Johannes Berg
Cc: Shuah Khan, mingo, will, kvalo, davem, kuba, ath10k,
linux-wireless, netdev, linux-kernel
On Mon, Feb 15, 2021 at 02:12:30PM +0100, Johannes Berg wrote:
> On Mon, 2021-02-15 at 11:44 +0100, Peter Zijlstra wrote:
> >
> > I think something like so will work, but please double check.
>
> Yeah, that looks better.
>
> > +++ b/include/linux/lockdep.h
> > @@ -294,11 +294,15 @@ extern void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie);
> >
> > #define lockdep_depth(tsk) (debug_locks ? (tsk)->lockdep_depth : 0)
> >
> > -#define lockdep_assert_held(l) do { \
> > - WARN_ON(debug_locks && !lockdep_is_held(l)); \
> > +#define lockdep_assert_held(l) do { \
> > + WARN_ON(debug_locks && lockdep_is_held(l) == 0)); \
> > } while (0)
>
> That doesn't really need to change? It's the same.
Correct, but I found it more symmetric vs the not implementation below.
> > -#define lockdep_assert_held_write(l) do { \
> > +#define lockdep_assert_not_held(l) do { \
> > + WARN_ON(debug_locks && lockdep_is_held(l) == 1)); \
> > + } while (0)
> > +
> > +#define lockdep_assert_held_write(l) do { \
> > WARN_ON(debug_locks && !lockdep_is_held_type(l, 0)); \
> > } while (0)
> >
> > diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> > index c1418b47f625..983ba206f7b2 100644
> > --- a/kernel/locking/lockdep.
> > +++ b/kernel/locking/lockdep.c
> > @@ -5467,7 +5467,7 @@ noinstr int lock_is_held_type(const struct lockdep_map *lock, int read)
> > int ret = 0;
> >
> > if (unlikely(!lockdep_enabled()))
> > - return 1; /* avoid false negative lockdep_assert_held() */
> > + return -1; /* avoid false negative lockdep_assert_held() */
>
> Maybe add lockdep_assert_not_held() to the comment, to explain the -1
> (vs non-zero)?
Yeah, or frob a '*' in there.
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH 1/2] lockdep: add lockdep_assert_not_held()
2021-02-15 16:04 ` Peter Zijlstra
@ 2021-02-15 16:10 ` Johannes Berg
2021-02-22 20:51 ` Shuah Khan
0 siblings, 1 reply; 10+ messages in thread
From: Johannes Berg @ 2021-02-15 16:10 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Shuah Khan, mingo, will, kvalo, davem, kuba, ath10k,
linux-wireless, netdev, linux-kernel
On Mon, 2021-02-15 at 17:04 +0100, Peter Zijlstra wrote:
> On Mon, Feb 15, 2021 at 02:12:30PM +0100, Johannes Berg wrote:
> > On Mon, 2021-02-15 at 11:44 +0100, Peter Zijlstra wrote:
> > > I think something like so will work, but please double check.
> >
> > Yeah, that looks better.
> >
> > > +++ b/include/linux/lockdep.h
> > > @@ -294,11 +294,15 @@ extern void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie);
> > >
> > > #define lockdep_depth(tsk) (debug_locks ? (tsk)->lockdep_depth : 0)
> > >
> > > -#define lockdep_assert_held(l) do { \
> > > - WARN_ON(debug_locks && !lockdep_is_held(l)); \
> > > +#define lockdep_assert_held(l) do { \
> > > + WARN_ON(debug_locks && lockdep_is_held(l) == 0)); \
> > > } while (0)
> >
> > That doesn't really need to change? It's the same.
>
> Correct, but I found it more symmetric vs the not implementation below.
Fair enough. One might argue that you should have an
enum lockdep_lock_state {
LOCK_STATE_NOT_HELD, /* 0 now */
LOCK_STATE_HELD, /* 1 now */
LOCK_STATE_UNKNOWN, /* -1 with your patch but might as well be 2 */
};
:)
johannes
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH 1/2] lockdep: add lockdep_assert_not_held()
2021-02-15 16:10 ` Johannes Berg
@ 2021-02-22 20:51 ` Shuah Khan
0 siblings, 0 replies; 10+ messages in thread
From: Shuah Khan @ 2021-02-22 20:51 UTC (permalink / raw)
To: Johannes Berg, Peter Zijlstra
Cc: mingo, will, kvalo, davem, kuba, ath10k, linux-wireless, netdev,
linux-kernel, Shuah Khan
On 2/15/21 9:10 AM, Johannes Berg wrote:
> On Mon, 2021-02-15 at 17:04 +0100, Peter Zijlstra wrote:
>> On Mon, Feb 15, 2021 at 02:12:30PM +0100, Johannes Berg wrote:
>>> On Mon, 2021-02-15 at 11:44 +0100, Peter Zijlstra wrote:
>>>> I think something like so will work, but please double check.
>>>
>>> Yeah, that looks better.
>>>
>>>> +++ b/include/linux/lockdep.h
>>>> @@ -294,11 +294,15 @@ extern void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie);
>>>>
>>>> #define lockdep_depth(tsk) (debug_locks ? (tsk)->lockdep_depth : 0)
>>>>
>>>> -#define lockdep_assert_held(l) do { \
>>>> - WARN_ON(debug_locks && !lockdep_is_held(l)); \
>>>> +#define lockdep_assert_held(l) do { \
>>>> + WARN_ON(debug_locks && lockdep_is_held(l) == 0)); \
>>>> } while (0)
>>>
>>> That doesn't really need to change? It's the same.
>>
>> Correct, but I found it more symmetric vs the not implementation below.
>
> Fair enough. One might argue that you should have an
>
> enum lockdep_lock_state {
> LOCK_STATE_NOT_HELD, /* 0 now */
> LOCK_STATE_HELD, /* 1 now */
> LOCK_STATE_UNKNOWN, /* -1 with your patch but might as well be 2 */
> };
>
> :)
>
Thank you both. Picking this back up. Will send v2 incorporating
your comments and suggestions.
thanks,
-- Shuah
^ permalink raw reply [flat|nested] 10+ messages in thread
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2021-02-12 23:28 ` [PATCH 1/2] lockdep: add lockdep_assert_not_held() Shuah Khan
2021-02-14 17:53 ` Peter Zijlstra
2021-02-15 10:44 ` Peter Zijlstra
2021-02-15 13:12 ` Johannes Berg
2021-02-15 16:04 ` Peter Zijlstra
2021-02-15 16:10 ` Johannes Berg
2021-02-22 20:51 ` Shuah Khan
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