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[PATCH v2 6/7] apei/ghes: Use unrcu_pointer for cmpxchg

Jia He posted 7 patches 3 years, 7 months ago
[PATCH v2 6/7] apei/ghes: Use unrcu_pointer for cmpxchg
Posted by Jia He 3 years, 7 months ago 
ghes_estatus_caches should be add rcu annotation to avoid sparse warnings.
   drivers/acpi/apei/ghes.c:733:25: sparse: sparse: incompatible types in comparison expression (different address spaces):
   drivers/acpi/apei/ghes.c:733:25: sparse:    struct ghes_estatus_cache [noderef] __rcu *
   drivers/acpi/apei/ghes.c:733:25: sparse:    struct ghes_estatus_cache *
   drivers/acpi/apei/ghes.c:813:25: sparse: sparse: incompatible types in comparison expression (different address spaces):
   drivers/acpi/apei/ghes.c:813:25: sparse:    struct ghes_estatus_cache [noderef] __rcu *
   drivers/acpi/apei/ghes.c:813:25: sparse:    struct ghes_estatus_cache *

unrcu_pointer is to strip the __rcu in cmpxchg.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Jia He <justin.he@arm.com>
---
 drivers/acpi/apei/ghes.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
index 9272d963b57d..92ae58f4f7bb 100644
--- a/drivers/acpi/apei/ghes.c
+++ b/drivers/acpi/apei/ghes.c
@@ -144,7 +144,7 @@ struct ghes_vendor_record_entry {
 static struct gen_pool *ghes_estatus_pool;
 static unsigned long ghes_estatus_pool_size_request;
 
-static struct ghes_estatus_cache *ghes_estatus_caches[GHES_ESTATUS_CACHES_SIZE];
+static struct ghes_estatus_cache __rcu *ghes_estatus_caches[GHES_ESTATUS_CACHES_SIZE];
 static atomic_t ghes_estatus_cache_alloced;
 
 static int ghes_panic_timeout __read_mostly = 30;
@@ -834,8 +834,9 @@ static void ghes_estatus_cache_add(
 	}
 	/* new_cache must be put into array after its contents are written */
 	smp_wmb();
-	if (slot != -1 && cmpxchg(ghes_estatus_caches + slot,
-				  slot_cache, new_cache) == slot_cache) {
+	if (slot != -1 && unrcu_pointer(cmpxchg(ghes_estatus_caches + slot,
+				RCU_INITIALIZER(slot_cache),
+				RCU_INITIALIZER(new_cache)))) {
 		if (slot_cache)
 			call_rcu(&slot_cache->rcu, ghes_estatus_cache_rcu_free);
 	} else
-- 
2.25.1
RE: [PATCH v2 6/7] apei/ghes: Use unrcu_pointer for cmpxchg
Posted by David Laight 3 years, 7 months ago 
From: Jia He
> Sent: 17 August 2022 15:35
> 
> ghes_estatus_caches should be add rcu annotation to avoid sparse warnings.
>    drivers/acpi/apei/ghes.c:733:25: sparse: sparse: incompatible types in comparison expression
> (different address spaces):
>    drivers/acpi/apei/ghes.c:733:25: sparse:    struct ghes_estatus_cache [noderef] __rcu *
>    drivers/acpi/apei/ghes.c:733:25: sparse:    struct ghes_estatus_cache *
>    drivers/acpi/apei/ghes.c:813:25: sparse: sparse: incompatible types in comparison expression
> (different address spaces):
>    drivers/acpi/apei/ghes.c:813:25: sparse:    struct ghes_estatus_cache [noderef] __rcu *
>    drivers/acpi/apei/ghes.c:813:25: sparse:    struct ghes_estatus_cache *
> 
> unrcu_pointer is to strip the __rcu in cmpxchg.
> 
> Reported-by: kernel test robot <lkp@intel.com>
> Signed-off-by: Jia He <justin.he@arm.com>
> ---
>  drivers/acpi/apei/ghes.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
> index 9272d963b57d..92ae58f4f7bb 100644
> --- a/drivers/acpi/apei/ghes.c
> +++ b/drivers/acpi/apei/ghes.c
> @@ -144,7 +144,7 @@ struct ghes_vendor_record_entry {
>  static struct gen_pool *ghes_estatus_pool;
>  static unsigned long ghes_estatus_pool_size_request;
> 
> -static struct ghes_estatus_cache *ghes_estatus_caches[GHES_ESTATUS_CACHES_SIZE];
> +static struct ghes_estatus_cache __rcu *ghes_estatus_caches[GHES_ESTATUS_CACHES_SIZE];
>  static atomic_t ghes_estatus_cache_alloced;
> 
>  static int ghes_panic_timeout __read_mostly = 30;
> @@ -834,8 +834,9 @@ static void ghes_estatus_cache_add(
>  	}
>  	/* new_cache must be put into array after its contents are written */
>  	smp_wmb();
> -	if (slot != -1 && cmpxchg(ghes_estatus_caches + slot,
> -				  slot_cache, new_cache) == slot_cache) {
> +	if (slot != -1 && unrcu_pointer(cmpxchg(ghes_estatus_caches + slot,
> +				RCU_INITIALIZER(slot_cache),
> +				RCU_INITIALIZER(new_cache)))) {

Did you test this?
There seems to be an == missing.

	David

>  		if (slot_cache)
>  			call_rcu(&slot_cache->rcu, ghes_estatus_cache_rcu_free);
>  	} else
> --
> 2.25.1

-
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Registration No: 1397386 (Wales)
RE: [PATCH v2 6/7] apei/ghes: Use unrcu_pointer for cmpxchg
Posted by Justin He 3 years, 7 months ago 

> -----Original Message-----
> From: David Laight <David.Laight@ACULAB.COM>
> Sent: Wednesday, August 17, 2022 11:39 PM
> To: Justin He <Justin.He@arm.com>; Ard Biesheuvel <ardb@kernel.org>; Len
> Brown <lenb@kernel.org>; James Morse <James.Morse@arm.com>; Tony
> Luck <tony.luck@intel.com>; Borislav Petkov <bp@alien8.de>; Mauro
> Carvalho Chehab <mchehab@kernel.org>; Robert Richter <rric@kernel.org>;
> Robert Moore <robert.moore@intel.com>; Qiuxu Zhuo
> <qiuxu.zhuo@intel.com>; Yazen Ghannam <yazen.ghannam@amd.com>
> Cc: linux-acpi@vger.kernel.org; linux-kernel@vger.kernel.org;
> linux-edac@vger.kernel.org; devel@acpica.org; Rafael J . Wysocki
> <rafael@kernel.org>; Shuai Xue <xueshuai@linux.alibaba.com>; Jarkko
> Sakkinen <jarkko@kernel.org>; linux-efi@vger.kernel.org;
> toshi.kani@hpe.com; nd <nd@arm.com>; kernel test robot <lkp@intel.com>
> Subject: RE: [PATCH v2 6/7] apei/ghes: Use unrcu_pointer for cmpxchg
> 
> From: Jia He
> > Sent: 17 August 2022 15:35
> >
> > ghes_estatus_caches should be add rcu annotation to avoid sparse
> warnings.
> >    drivers/acpi/apei/ghes.c:733:25: sparse: sparse: incompatible types
> > in comparison expression (different address spaces):
> >    drivers/acpi/apei/ghes.c:733:25: sparse:    struct
> ghes_estatus_cache [noderef] __rcu *
> >    drivers/acpi/apei/ghes.c:733:25: sparse:    struct
> ghes_estatus_cache *
> >    drivers/acpi/apei/ghes.c:813:25: sparse: sparse: incompatible types
> > in comparison expression (different address spaces):
> >    drivers/acpi/apei/ghes.c:813:25: sparse:    struct
> ghes_estatus_cache [noderef] __rcu *
> >    drivers/acpi/apei/ghes.c:813:25: sparse:    struct
> ghes_estatus_cache *
> >
> > unrcu_pointer is to strip the __rcu in cmpxchg.
> >
> > Reported-by: kernel test robot <lkp@intel.com>
> > Signed-off-by: Jia He <justin.he@arm.com>
> > ---
> >  drivers/acpi/apei/ghes.c | 7 ++++---
> >  1 file changed, 4 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c index
> > 9272d963b57d..92ae58f4f7bb 100644
> > --- a/drivers/acpi/apei/ghes.c
> > +++ b/drivers/acpi/apei/ghes.c
> > @@ -144,7 +144,7 @@ struct ghes_vendor_record_entry {  static struct
> > gen_pool *ghes_estatus_pool;  static unsigned long
> > ghes_estatus_pool_size_request;
> >
> > -static struct ghes_estatus_cache
> > *ghes_estatus_caches[GHES_ESTATUS_CACHES_SIZE];
> > +static struct ghes_estatus_cache __rcu
> > +*ghes_estatus_caches[GHES_ESTATUS_CACHES_SIZE];
> >  static atomic_t ghes_estatus_cache_alloced;
> >
> >  static int ghes_panic_timeout __read_mostly = 30; @@ -834,8 +834,9
> @@
> > static void ghes_estatus_cache_add(
> >  	}
> >  	/* new_cache must be put into array after its contents are written */
> >  	smp_wmb();
> > -	if (slot != -1 && cmpxchg(ghes_estatus_caches + slot,
> > -				  slot_cache, new_cache) == slot_cache) {
> > +	if (slot != -1 && unrcu_pointer(cmpxchg(ghes_estatus_caches + slot,
> > +				RCU_INITIALIZER(slot_cache),
> > +				RCU_INITIALIZER(new_cache)))) {
> 
> Did you test this?
> There seems to be an == missing.

Sorry about it, 


--
Cheers,
Justin (Jia He)

Patchew 2.1-devel-ea86937

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