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From:   Jia He <justin.he@arm.com>
To:     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@arm.com, Jia He <justin.he@arm.com>,
        kernel test robot <lkp@intel.com>
Subject: [PATCH v2 6/7] apei/ghes: Use unrcu_pointer for cmpxchg
Date:   Wed, 17 Aug 2022 14:34:57 +0000
Message-Id: <20220817143458.335938-7-justin.he@arm.com>
In-Reply-To: <20220817143458.335938-1-justin.he@arm.com>
References: <20220817143458.335938-1-justin.he@arm.com>
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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