linux-kernel - [PATCH v4 7/8] apei/ghes: Use unrcu

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Date:   Wed, 31 Aug 2022 07:40:26 +0000
From:   Jia He <justin.he@....com>
To:     Len Brown <lenb@...nel.org>, James Morse <james.morse@....com>,
        Tony Luck <tony.luck@...el.com>,
        Borislav Petkov <bp@...en8.de>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Robert Richter <rric@...nel.org>,
        Robert Moore <robert.moore@...el.com>,
        Qiuxu Zhuo <qiuxu.zhuo@...el.com>,
        Yazen Ghannam <yazen.ghannam@....com>,
        Jan Luebbe <jlu@...gutronix.de>,
        Khuong Dinh <khuong@...amperecomputing.com>,
        Kani Toshi <toshi.kani@....com>
Cc:     Ard Biesheuvel <ardb@...nel.org>, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-edac@...r.kernel.org,
        devel@...ica.org, "Rafael J . Wysocki" <rafael@...nel.org>,
        Shuai Xue <xueshuai@...ux.alibaba.com>,
        Jarkko Sakkinen <jarkko@...nel.org>, linux-efi@...r.kernel.org,
        nd@....com, Jia He <justin.he@....com>,
        kernel test robot <lkp@...el.com>
Subject: [PATCH v4 7/8] apei/ghes: Use unrcu_pointer for cmpxchg

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@...el.com>
Signed-off-by: Jia He <justin.he@....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 d11e3b2e5345..bbd96e91bec1 100644
--- a/drivers/acpi/apei/ghes.c
+++ b/drivers/acpi/apei/ghes.c
@@ -153,7 +153,7 @@ 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;
@@ -843,8 +843,9 @@ 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))) == slot_cache) {
 		if (slot_cache)
 			call_rcu(&slot_cache->rcu, ghes_estatus_cache_rcu_free);
 	} else
-- 
2.25.1