2019-12-10 03:32:30

by Paul E. McKenney

[permalink] [raw]
Subject: [PATCH net/tipc] Replace rcu_swap_protected() with rcu_replace_pointer()

This commit replaces the use of rcu_swap_protected() with the more
intuitively appealing rcu_replace_pointer() as a step towards removing
rcu_swap_protected().

Link: https://lore.kernel.org/lkml/CAHk-=wiAsJLw1egFEE=Z7-GGtM6wcvtyytXZA1+BHqta4gg6Hw@mail.gmail.com/
Reported-by: Linus Torvalds <[email protected]>
Reported-by: kbuild test robot <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
Cc: Jon Maloy <[email protected]>
Cc: Ying Xue <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: <[email protected]>
Cc: <[email protected]>

diff --git a/net/tipc/crypto.c b/net/tipc/crypto.c
index 990a872..64cf831 100644
--- a/net/tipc/crypto.c
+++ b/net/tipc/crypto.c
@@ -258,7 +258,7 @@ static char *tipc_key_change_dump(struct tipc_key old, struct tipc_key new,
rcu_dereference_protected((rcu_ptr), lockdep_is_held(lock))

#define tipc_aead_rcu_swap(rcu_ptr, ptr, lock) \
- rcu_swap_protected((rcu_ptr), (ptr), lockdep_is_held(lock))
+ rcu_replace_pointer((rcu_ptr), (ptr), lockdep_is_held(lock))

#define tipc_aead_rcu_replace(rcu_ptr, ptr, lock) \
do { \
@@ -1189,7 +1189,7 @@ static bool tipc_crypto_key_try_align(struct tipc_crypto *rx, u8 new_pending)

/* Move passive key if any */
if (key.passive) {
- tipc_aead_rcu_swap(rx->aead[key.passive], tmp2, &rx->lock);
+ tmp2 = rcu_replace_pointer(rx->aead[key.passive], tmp2, &rx->lock);
x = (key.passive - key.pending + new_pending) % KEY_MAX;
new_passive = (x <= 0) ? x + KEY_MAX : x;
}


2019-12-10 16:00:51

by Ying Xue

[permalink] [raw]
Subject: Re: [PATCH net/tipc] Replace rcu_swap_protected() with rcu_replace_pointer()

On 12/10/19 11:31 AM, Paul E. McKenney wrote:
> This commit replaces the use of rcu_swap_protected() with the more
> intuitively appealing rcu_replace_pointer() as a step towards removing
> rcu_swap_protected().
>
> Link: https://lore.kernel.org/lkml/CAHk-=wiAsJLw1egFEE=Z7-GGtM6wcvtyytXZA1+BHqta4gg6Hw@mail.gmail.com/
> Reported-by: Linus Torvalds <[email protected]>
> Reported-by: kbuild test robot <[email protected]>
> Signed-off-by: Paul E. McKenney <[email protected]>
> Cc: Jon Maloy <[email protected]>
> Cc: Ying Xue <[email protected]>
> Cc: "David S. Miller" <[email protected]>
> Cc: <[email protected]>
> Cc: <[email protected]>
>
> diff --git a/net/tipc/crypto.c b/net/tipc/crypto.c
> index 990a872..64cf831 100644
> --- a/net/tipc/crypto.c
> +++ b/net/tipc/crypto.c
> @@ -258,7 +258,7 @@ static char *tipc_key_change_dump(struct tipc_key old, struct tipc_key new,
> rcu_dereference_protected((rcu_ptr), lockdep_is_held(lock))
>
> #define tipc_aead_rcu_swap(rcu_ptr, ptr, lock) \
> - rcu_swap_protected((rcu_ptr), (ptr), lockdep_is_held(lock))
> + rcu_replace_pointer((rcu_ptr), (ptr), lockdep_is_held(lock))

(ptr) = rcu_replace_pointer((rcu_ptr), (ptr), lockdep_is_held(lock))

>
> #define tipc_aead_rcu_replace(rcu_ptr, ptr, lock) \
> do { \
> @@ -1189,7 +1189,7 @@ static bool tipc_crypto_key_try_align(struct tipc_crypto *rx, u8 new_pending)
>
> /* Move passive key if any */
> if (key.passive) {
> - tipc_aead_rcu_swap(rx->aead[key.passive], tmp2, &rx->lock);
> + tmp2 = rcu_replace_pointer(rx->aead[key.passive], tmp2, &rx->lock);

tipc_aead_rcu_swap() is only called here in TIPC module. If we use
rcu_replace_pointer() to switch pointers instead of calling
tipc_aead_rcu_swap() macro, I think we should completely remove
tipc_aead_rcu_swap().

> x = (key.passive - key.pending + new_pending) % KEY_MAX;
> new_passive = (x <= 0) ? x + KEY_MAX : x;
> }
>

2019-12-10 22:40:02

by Paul E. McKenney

[permalink] [raw]
Subject: Re: [PATCH net/tipc] Replace rcu_swap_protected() with rcu_replace_pointer()

On Tue, Dec 10, 2019 at 10:36:59PM +0800, Ying Xue wrote:
> On 12/10/19 11:31 AM, Paul E. McKenney wrote:
> > This commit replaces the use of rcu_swap_protected() with the more
> > intuitively appealing rcu_replace_pointer() as a step towards removing
> > rcu_swap_protected().
> >
> > Link: https://lore.kernel.org/lkml/CAHk-=wiAsJLw1egFEE=Z7-GGtM6wcvtyytXZA1+BHqta4gg6Hw@mail.gmail.com/
> > Reported-by: Linus Torvalds <[email protected]>
> > Reported-by: kbuild test robot <[email protected]>
> > Signed-off-by: Paul E. McKenney <[email protected]>
> > Cc: Jon Maloy <[email protected]>
> > Cc: Ying Xue <[email protected]>
> > Cc: "David S. Miller" <[email protected]>
> > Cc: <[email protected]>
> > Cc: <[email protected]>
> >
> > diff --git a/net/tipc/crypto.c b/net/tipc/crypto.c
> > index 990a872..64cf831 100644
> > --- a/net/tipc/crypto.c
> > +++ b/net/tipc/crypto.c
> > @@ -258,7 +258,7 @@ static char *tipc_key_change_dump(struct tipc_key old, struct tipc_key new,
> > rcu_dereference_protected((rcu_ptr), lockdep_is_held(lock))
> >
> > #define tipc_aead_rcu_swap(rcu_ptr, ptr, lock) \
> > - rcu_swap_protected((rcu_ptr), (ptr), lockdep_is_held(lock))
> > + rcu_replace_pointer((rcu_ptr), (ptr), lockdep_is_held(lock))
>
> (ptr) = rcu_replace_pointer((rcu_ptr), (ptr), lockdep_is_held(lock))
>
> >
> > #define tipc_aead_rcu_replace(rcu_ptr, ptr, lock) \
> > do { \
> > @@ -1189,7 +1189,7 @@ static bool tipc_crypto_key_try_align(struct tipc_crypto *rx, u8 new_pending)
> >
> > /* Move passive key if any */
> > if (key.passive) {
> > - tipc_aead_rcu_swap(rx->aead[key.passive], tmp2, &rx->lock);
> > + tmp2 = rcu_replace_pointer(rx->aead[key.passive], tmp2, &rx->lock);
>
> tipc_aead_rcu_swap() is only called here in TIPC module. If we use
> rcu_replace_pointer() to switch pointers instead of calling
> tipc_aead_rcu_swap() macro, I think we should completely remove
> tipc_aead_rcu_swap().

Good catch, thank you! How about the following instead?

Thanx, Paul

------------------------------------------------------------------------

commit 4ee8e2c68b076867b7a5af82a38010fffcab611c
Author: Paul E. McKenney <[email protected]>
Date: Mon Dec 9 19:13:45 2019 -0800

net/tipc: Replace rcu_swap_protected() with rcu_replace_pointer()

This commit replaces the use of rcu_swap_protected() with the more
intuitively appealing rcu_replace_pointer() as a step towards removing
rcu_swap_protected().

Link: https://lore.kernel.org/lkml/CAHk-=wiAsJLw1egFEE=Z7-GGtM6wcvtyytXZA1+BHqta4gg6Hw@mail.gmail.com/
Reported-by: Linus Torvalds <[email protected]>
Reported-by: kbuild test robot <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
Cc: Jon Maloy <[email protected]>
Cc: Ying Xue <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: <[email protected]>
Cc: <[email protected]>

diff --git a/net/tipc/crypto.c b/net/tipc/crypto.c
index 990a872..978d2db 100644
--- a/net/tipc/crypto.c
+++ b/net/tipc/crypto.c
@@ -257,9 +257,6 @@ static char *tipc_key_change_dump(struct tipc_key old, struct tipc_key new,
#define tipc_aead_rcu_ptr(rcu_ptr, lock) \
rcu_dereference_protected((rcu_ptr), lockdep_is_held(lock))

-#define tipc_aead_rcu_swap(rcu_ptr, ptr, lock) \
- rcu_swap_protected((rcu_ptr), (ptr), lockdep_is_held(lock))
-
#define tipc_aead_rcu_replace(rcu_ptr, ptr, lock) \
do { \
typeof(rcu_ptr) __tmp = rcu_dereference_protected((rcu_ptr), \
@@ -1189,7 +1186,7 @@ static bool tipc_crypto_key_try_align(struct tipc_crypto *rx, u8 new_pending)

/* Move passive key if any */
if (key.passive) {
- tipc_aead_rcu_swap(rx->aead[key.passive], tmp2, &rx->lock);
+ tmp2 = rcu_replace_pointer(rx->aead[key.passive], tmp2, &rx->lock);
x = (key.passive - key.pending + new_pending) % KEY_MAX;
new_passive = (x <= 0) ? x + KEY_MAX : x;
}

2019-12-11 01:46:37

by Ying Xue

[permalink] [raw]
Subject: Re: [PATCH net/tipc] Replace rcu_swap_protected() with rcu_replace_pointer()

On 12/11/19 6:38 AM, Paul E. McKenney wrote:
> commit 4ee8e2c68b076867b7a5af82a38010fffcab611c
> Author: Paul E. McKenney <[email protected]>
> Date: Mon Dec 9 19:13:45 2019 -0800
>
> net/tipc: Replace rcu_swap_protected() with rcu_replace_pointer()
>
> This commit replaces the use of rcu_swap_protected() with the more
> intuitively appealing rcu_replace_pointer() as a step towards removing
> rcu_swap_protected().
>
> Link: https://lore.kernel.org/lkml/CAHk-=wiAsJLw1egFEE=Z7-GGtM6wcvtyytXZA1+BHqta4gg6Hw@mail.gmail.com/
> Reported-by: Linus Torvalds <[email protected]>
> Reported-by: kbuild test robot <[email protected]>
> Signed-off-by: Paul E. McKenney <[email protected]>
> Cc: Jon Maloy <[email protected]>
> Cc: Ying Xue <[email protected]>
> Cc: "David S. Miller" <[email protected]>
> Cc: <[email protected]>
> Cc: <[email protected]>
>

Acked-by: Ying Xue <[email protected]>

> diff --git a/net/tipc/crypto.c b/net/tipc/crypto.c
> index 990a872..978d2db 100644
> --- a/net/tipc/crypto.c
> +++ b/net/tipc/crypto.c
> @@ -257,9 +257,6 @@ static char *tipc_key_change_dump(struct tipc_key old, struct tipc_key new,
> #define tipc_aead_rcu_ptr(rcu_ptr, lock) \
> rcu_dereference_protected((rcu_ptr), lockdep_is_held(lock))
>
> -#define tipc_aead_rcu_swap(rcu_ptr, ptr, lock) \
> - rcu_swap_protected((rcu_ptr), (ptr), lockdep_is_held(lock))
> -
> #define tipc_aead_rcu_replace(rcu_ptr, ptr, lock) \
> do { \
> typeof(rcu_ptr) __tmp = rcu_dereference_protected((rcu_ptr), \
> @@ -1189,7 +1186,7 @@ static bool tipc_crypto_key_try_align(struct tipc_crypto *rx, u8 new_pending)
>
> /* Move passive key if any */
> if (key.passive) {
> - tipc_aead_rcu_swap(rx->aead[key.passive], tmp2, &rx->lock);
> + tmp2 = rcu_replace_pointer(rx->aead[key.passive], tmp2, &rx->lock);
> x = (key.passive - key.pending + new_pending) % KEY_MAX;
> new_passive = (x <= 0) ? x + KEY_MAX : x;
> }
>

2019-12-11 02:11:17

by Tuong Tong Lien

[permalink] [raw]
Subject: RE: [tipc-discussion] [PATCH net/tipc] Replace rcu_swap_protected() with rcu_replace_pointer()

Hi Ying, Paul,

Please see my comments inline. Thanks!

BR/Tuong

-----Original Message-----
From: Ying Xue <[email protected]>
Sent: Wednesday, December 11, 2019 8:32 AM
To: [email protected]
Cc: [email protected]; [email protected]; [email protected];
[email protected]; [email protected];
[email protected]; [email protected]
Subject: Re: [tipc-discussion] [PATCH net/tipc] Replace rcu_swap_protected()
with rcu_replace_pointer()

On 12/11/19 6:38 AM, Paul E. McKenney wrote:
> commit 4ee8e2c68b076867b7a5af82a38010fffcab611c
> Author: Paul E. McKenney <[email protected]>
> Date: Mon Dec 9 19:13:45 2019 -0800
>
> net/tipc: Replace rcu_swap_protected() with rcu_replace_pointer()
>
> This commit replaces the use of rcu_swap_protected() with the more
> intuitively appealing rcu_replace_pointer() as a step towards removing
> rcu_swap_protected().
>
> Link:
https://lore.kernel.org/lkml/CAHk-=wiAsJLw1egFEE=Z7-GGtM6wcvtyytXZA1+BHqta4g
[email protected]/
> Reported-by: Linus Torvalds <[email protected]>
> Reported-by: kbuild test robot <[email protected]>
> Signed-off-by: Paul E. McKenney <[email protected]>
> Cc: Jon Maloy <[email protected]>
> Cc: Ying Xue <[email protected]>
> Cc: "David S. Miller" <[email protected]>
> Cc: <[email protected]>
> Cc: <[email protected]>
>

Acked-by: Ying Xue <[email protected]>

> diff --git a/net/tipc/crypto.c b/net/tipc/crypto.c
> index 990a872..978d2db 100644
> --- a/net/tipc/crypto.c
> +++ b/net/tipc/crypto.c
> @@ -257,9 +257,6 @@ static char *tipc_key_change_dump(struct tipc_key old,
struct tipc_key new,
> #define tipc_aead_rcu_ptr(rcu_ptr, lock) \
> rcu_dereference_protected((rcu_ptr), lockdep_is_held(lock))
>
> -#define tipc_aead_rcu_swap(rcu_ptr, ptr, lock)
\
> - rcu_swap_protected((rcu_ptr), (ptr), lockdep_is_held(lock))
> -
> #define tipc_aead_rcu_replace(rcu_ptr, ptr, lock) \
> do { \
> typeof(rcu_ptr) __tmp = rcu_dereference_protected((rcu_ptr), \
> @@ -1189,7 +1186,7 @@ static bool tipc_crypto_key_try_align(struct
tipc_crypto *rx, u8 new_pending)
>
> /* Move passive key if any */
> if (key.passive) {
> - tipc_aead_rcu_swap(rx->aead[key.passive], tmp2, &rx->lock);
> + tmp2 = rcu_replace_pointer(rx->aead[key.passive], tmp2,
&rx->lock);
The 3rd parameter should be the lockdep condition checking instead of the
spinlock's pointer i.e. "lockdep_is_held(&rx->lock)"?
That's why I'd prefer to use the 'tipc_aead_rcu_swap ()' macro, which is
clear & concise at least for the context here. It might be re-used later as
well...

> x = (key.passive - key.pending + new_pending) % KEY_MAX;
> new_passive = (x <= 0) ? x + KEY_MAX : x;
> }
>


_______________________________________________
tipc-discussion mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/tipc-discussion

2019-12-11 03:18:36

by Paul E. McKenney

[permalink] [raw]
Subject: Re: [tipc-discussion] [PATCH net/tipc] Replace rcu_swap_protected() with rcu_replace_pointer()

On Wed, Dec 11, 2019 at 09:00:39AM +0700, Tuong Lien Tong wrote:
> Hi Ying, Paul,
>
> Please see my comments inline. Thanks!

Good catch!

> BR/Tuong
>
> -----Original Message-----
> From: Ying Xue <[email protected]>
> Sent: Wednesday, December 11, 2019 8:32 AM
> To: [email protected]
> Cc: [email protected]; [email protected]; [email protected];
> [email protected]; [email protected];
> [email protected]; [email protected]
> Subject: Re: [tipc-discussion] [PATCH net/tipc] Replace rcu_swap_protected()
> with rcu_replace_pointer()
>
> On 12/11/19 6:38 AM, Paul E. McKenney wrote:
> > commit 4ee8e2c68b076867b7a5af82a38010fffcab611c
> > Author: Paul E. McKenney <[email protected]>
> > Date: Mon Dec 9 19:13:45 2019 -0800
> >
> > net/tipc: Replace rcu_swap_protected() with rcu_replace_pointer()
> >
> > This commit replaces the use of rcu_swap_protected() with the more
> > intuitively appealing rcu_replace_pointer() as a step towards removing
> > rcu_swap_protected().
> >
> > Link:
> https://lore.kernel.org/lkml/CAHk-=wiAsJLw1egFEE=Z7-GGtM6wcvtyytXZA1+BHqta4g
> [email protected]/
> > Reported-by: Linus Torvalds <[email protected]>
> > Reported-by: kbuild test robot <[email protected]>
> > Signed-off-by: Paul E. McKenney <[email protected]>
> > Cc: Jon Maloy <[email protected]>
> > Cc: Ying Xue <[email protected]>
> > Cc: "David S. Miller" <[email protected]>
> > Cc: <[email protected]>
> > Cc: <[email protected]>
>
> Acked-by: Ying Xue <[email protected]>

As in the following? If so, I will be very happy to apply your Acked-by.

Thanx, Paul

------------------------------------------------------------------------

commit 4c0855120704e7a578dc6862ae57babf6dc9bc77
Author: Paul E. McKenney <[email protected]>
Date: Mon Dec 9 19:13:45 2019 -0800

net/tipc: Replace rcu_swap_protected() with rcu_replace_pointer()

This commit replaces the use of rcu_swap_protected() with the more
intuitively appealing rcu_replace_pointer() as a step towards removing
rcu_swap_protected().

Link: https://lore.kernel.org/lkml/CAHk-=wiAsJLw1egFEE=Z7-GGtM6wcvtyytXZA1+BHqta4gg6Hw@mail.gmail.com/
Reported-by: Linus Torvalds <[email protected]>
Reported-by: kbuild test robot <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
[ paulmck: Updated based on Ying Xue and Tuong Lien Tong feedback. ]
Cc: Jon Maloy <[email protected]>
Cc: Ying Xue <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: <[email protected]>
Cc: <[email protected]>

diff --git a/net/tipc/crypto.c b/net/tipc/crypto.c
index 990a872..39a13b4 100644
--- a/net/tipc/crypto.c
+++ b/net/tipc/crypto.c
@@ -258,7 +258,7 @@ static char *tipc_key_change_dump(struct tipc_key old, struct tipc_key new,
rcu_dereference_protected((rcu_ptr), lockdep_is_held(lock))

#define tipc_aead_rcu_swap(rcu_ptr, ptr, lock) \
- rcu_swap_protected((rcu_ptr), (ptr), lockdep_is_held(lock))
+ rcu_replace_pointer((rcu_ptr), (ptr), lockdep_is_held(lock))

#define tipc_aead_rcu_replace(rcu_ptr, ptr, lock) \
do { \
@@ -1189,7 +1189,7 @@ static bool tipc_crypto_key_try_align(struct tipc_crypto *rx, u8 new_pending)

/* Move passive key if any */
if (key.passive) {
- tipc_aead_rcu_swap(rx->aead[key.passive], tmp2, &rx->lock);
+ tmp2 = tipc_aead_rcu_swap(rx->aead[key.passive], tmp2, &rx->lock);
x = (key.passive - key.pending + new_pending) % KEY_MAX;
new_passive = (x <= 0) ? x + KEY_MAX : x;
}

2019-12-11 04:51:01

by Ying Xue

[permalink] [raw]
Subject: Re: [tipc-discussion] [PATCH net/tipc] Replace rcu_swap_protected() with rcu_replace_pointer()

On 12/11/19 11:17 AM, Paul E. McKenney wrote:
>> Acked-by: Ying Xue <[email protected]>
> As in the following? If so, I will be very happy to apply your Acked-by.

Yes. Thanks!

2019-12-11 04:56:21

by Ying Xue

[permalink] [raw]
Subject: Re: [tipc-discussion] [PATCH net/tipc] Replace rcu_swap_protected() with rcu_replace_pointer()

On 12/11/19 10:00 AM, Tuong Lien Tong wrote:
>>
>> /* Move passive key if any */
>> if (key.passive) {
>> - tipc_aead_rcu_swap(rx->aead[key.passive], tmp2, &rx->lock);
>> + tmp2 = rcu_replace_pointer(rx->aead[key.passive], tmp2,
> &rx->lock);
> The 3rd parameter should be the lockdep condition checking instead of the
> spinlock's pointer i.e. "lockdep_is_held(&rx->lock)"?
> That's why I'd prefer to use the 'tipc_aead_rcu_swap ()' macro, which is
> clear & concise at least for the context here. It might be re-used later as
> well...
>

Right. The 3rd parameter of rcu_replace_pointer() should be
"lockdep_is_held(&rx->lock)" instead of "&rx->lock".

2019-12-11 18:47:01

by Paul E. McKenney

[permalink] [raw]
Subject: Re: [tipc-discussion] [PATCH net/tipc] Replace rcu_swap_protected() with rcu_replace_pointer()

On Wed, Dec 11, 2019 at 12:42:00PM +0800, Ying Xue wrote:
> On 12/11/19 10:00 AM, Tuong Lien Tong wrote:
> >>
> >> /* Move passive key if any */
> >> if (key.passive) {
> >> - tipc_aead_rcu_swap(rx->aead[key.passive], tmp2, &rx->lock);
> >> + tmp2 = rcu_replace_pointer(rx->aead[key.passive], tmp2,
> > &rx->lock);
> > The 3rd parameter should be the lockdep condition checking instead of the
> > spinlock's pointer i.e. "lockdep_is_held(&rx->lock)"?
> > That's why I'd prefer to use the 'tipc_aead_rcu_swap ()' macro, which is
> > clear & concise at least for the context here. It might be re-used later as
> > well...
> >
>
> Right. The 3rd parameter of rcu_replace_pointer() should be
> "lockdep_is_held(&rx->lock)" instead of "&rx->lock".

Like this?

Thanx, Paul

------------------------------------------------------------------------

commit 575bb4ba1b22383656760feb3d122e11656ccdfd
Author: Paul E. McKenney <[email protected]>
Date: Mon Dec 9 19:13:45 2019 -0800

net/tipc: Replace rcu_swap_protected() with rcu_replace_pointer()

This commit replaces the use of rcu_swap_protected() with the more
intuitively appealing rcu_replace_pointer() as a step towards removing
rcu_swap_protected().

Link: https://lore.kernel.org/lkml/CAHk-=wiAsJLw1egFEE=Z7-GGtM6wcvtyytXZA1+BHqta4gg6Hw@mail.gmail.com/
Reported-by: Linus Torvalds <[email protected]>
Reported-by: kbuild test robot <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
[ paulmck: Updated based on Ying Xue and Tuong Lien Tong feedback. ]
Cc: Jon Maloy <[email protected]>
Cc: Ying Xue <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: <[email protected]>
Cc: <[email protected]>

diff --git a/net/tipc/crypto.c b/net/tipc/crypto.c
index 990a872..c8c47fc 100644
--- a/net/tipc/crypto.c
+++ b/net/tipc/crypto.c
@@ -257,9 +257,6 @@ static char *tipc_key_change_dump(struct tipc_key old, struct tipc_key new,
#define tipc_aead_rcu_ptr(rcu_ptr, lock) \
rcu_dereference_protected((rcu_ptr), lockdep_is_held(lock))

-#define tipc_aead_rcu_swap(rcu_ptr, ptr, lock) \
- rcu_swap_protected((rcu_ptr), (ptr), lockdep_is_held(lock))
-
#define tipc_aead_rcu_replace(rcu_ptr, ptr, lock) \
do { \
typeof(rcu_ptr) __tmp = rcu_dereference_protected((rcu_ptr), \
@@ -1189,7 +1186,7 @@ static bool tipc_crypto_key_try_align(struct tipc_crypto *rx, u8 new_pending)

/* Move passive key if any */
if (key.passive) {
- tipc_aead_rcu_swap(rx->aead[key.passive], tmp2, &rx->lock);
+ tmp2 = rcu_replace_pointer(rx->aead[key.passive], tmp2, lockdep_is_held(&rx->lock));
x = (key.passive - key.pending + new_pending) % KEY_MAX;
new_passive = (x <= 0) ? x + KEY_MAX : x;
}

2019-12-12 06:28:45

by Ying Xue

[permalink] [raw]
Subject: Re: [tipc-discussion] [PATCH net/tipc] Replace rcu_swap_protected() with rcu_replace_pointer()

On 12/12/19 2:46 AM, Paul E. McKenney wrote:
> On Wed, Dec 11, 2019 at 12:42:00PM +0800, Ying Xue wrote:
>> On 12/11/19 10:00 AM, Tuong Lien Tong wrote:
>>>>
>>>> /* Move passive key if any */
>>>> if (key.passive) {
>>>> - tipc_aead_rcu_swap(rx->aead[key.passive], tmp2, &rx->lock);
>>>> + tmp2 = rcu_replace_pointer(rx->aead[key.passive], tmp2,
>>> &rx->lock);
>>> The 3rd parameter should be the lockdep condition checking instead of the
>>> spinlock's pointer i.e. "lockdep_is_held(&rx->lock)"?
>>> That's why I'd prefer to use the 'tipc_aead_rcu_swap ()' macro, which is
>>> clear & concise at least for the context here. It might be re-used later as
>>> well...
>>>
>>
>> Right. The 3rd parameter of rcu_replace_pointer() should be
>> "lockdep_is_held(&rx->lock)" instead of "&rx->lock".
>
> Like this?

Yes, I think it's better to set the 3rd parameter of
rcu_replace_pointer() with "lockdep_is_held(&rx->lock)".

>
> Thanx, Paul
>
> ------------------------------------------------------------------------
>
> commit 575bb4ba1b22383656760feb3d122e11656ccdfd
> Author: Paul E. McKenney <[email protected]>
> Date: Mon Dec 9 19:13:45 2019 -0800
>
> net/tipc: Replace rcu_swap_protected() with rcu_replace_pointer()
>
> This commit replaces the use of rcu_swap_protected() with the more
> intuitively appealing rcu_replace_pointer() as a step towards removing
> rcu_swap_protected().
>
> Link: https://lore.kernel.org/lkml/CAHk-=wiAsJLw1egFEE=Z7-GGtM6wcvtyytXZA1+BHqta4gg6Hw@mail.gmail.com/
> Reported-by: Linus Torvalds <[email protected]>
> Reported-by: kbuild test robot <[email protected]>
> Signed-off-by: Paul E. McKenney <[email protected]>
> [ paulmck: Updated based on Ying Xue and Tuong Lien Tong feedback. ]
> Cc: Jon Maloy <[email protected]>
> Cc: Ying Xue <[email protected]>
> Cc: "David S. Miller" <[email protected]>
> Cc: <[email protected]>
> Cc: <[email protected]>
>
> diff --git a/net/tipc/crypto.c b/net/tipc/crypto.c
> index 990a872..c8c47fc 100644
> --- a/net/tipc/crypto.c
> +++ b/net/tipc/crypto.c
> @@ -257,9 +257,6 @@ static char *tipc_key_change_dump(struct tipc_key old, struct tipc_key new,
> #define tipc_aead_rcu_ptr(rcu_ptr, lock) \
> rcu_dereference_protected((rcu_ptr), lockdep_is_held(lock))
>
> -#define tipc_aead_rcu_swap(rcu_ptr, ptr, lock) \
> - rcu_swap_protected((rcu_ptr), (ptr), lockdep_is_held(lock))
> -
> #define tipc_aead_rcu_replace(rcu_ptr, ptr, lock) \
> do { \
> typeof(rcu_ptr) __tmp = rcu_dereference_protected((rcu_ptr), \
> @@ -1189,7 +1186,7 @@ static bool tipc_crypto_key_try_align(struct tipc_crypto *rx, u8 new_pending)
>
> /* Move passive key if any */
> if (key.passive) {
> - tipc_aead_rcu_swap(rx->aead[key.passive], tmp2, &rx->lock);
> + tmp2 = rcu_replace_pointer(rx->aead[key.passive], tmp2, lockdep_is_held(&rx->lock));
> x = (key.passive - key.pending + new_pending) % KEY_MAX;
> new_passive = (x <= 0) ? x + KEY_MAX : x;
> }
>