[PATCH 04/13] drivers/acpi/apei: convert seqno to seqnum_ops

[Shuah Khan]

seqnum_ops api is introduced to be used when a variable is used as
a sequence/stat counter and doesn't guard object lifetimes. This
clearly differentiates atomic_t usages that guard object lifetimes.

seqnum32 variables wrap around to INT_MIN when it overflows and
should not be used to guard resource lifetimes, device usage and
open counts that control state changes, and pm states.

seqno is a sequence number counter for logging. This counter gets
incremented. Unsure if there is a chance of this overflowing. It
doesn't look like overflowing causes any problems since it is used
to tag the log messages and nothing more. This conversion doesn't
change the overflow wrap around behavior.

Convert it to use seqnum_ops. This conversion replaces inc_return()
with _inc() followed by _read().

Signed-off-by: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>
---
 drivers/acpi/apei/ghes.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
index fce7ade2aba9..aa91998ce6f4 100644
--- a/drivers/acpi/apei/ghes.c
+++ b/drivers/acpi/apei/ghes.c
@@ -41,6 +41,7 @@
 #include <linux/uuid.h>
 #include <linux/ras.h>
 #include <linux/task_work.h>
+#include <linux/seqnum_ops.h>
 
 #include <acpi/actbl1.h>
 #include <acpi/ghes.h>
@@ -625,7 +626,7 @@ static void __ghes_print_estatus(const char *pfx,
 				 const struct acpi_hest_generic *generic,
 				 const struct acpi_hest_generic_status *estatus)
 {
-	static atomic_t seqno;
+	static struct seqnum32 seqno = SEQNUM_INIT(0);
 	unsigned int curr_seqno;
 	char pfx_seq[64];
 
@@ -636,7 +637,8 @@ static void __ghes_print_estatus(const char *pfx,
 		else
 			pfx = KERN_ERR;
 	}
-	curr_seqno = atomic_inc_return(&seqno);
+	seqnum32_inc(&seqno);
+	curr_seqno = seqnum32_read(&seqno);
 	snprintf(pfx_seq, sizeof(pfx_seq), "%s{%u}" HW_ERR, pfx, curr_seqno);
 	printk("%s""Hardware error from APEI Generic Hardware Error Source: %d\n",
 	       pfx_seq, generic->header.source_id);
-- 
2.27.0