linux-kernel - [RFC PATCH 05/11] drivers/acpi: convert seqno counter

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Message-Id: <9e2c6cccabc96fe1e5304e2fa2dfdad28ca5ac9c.1600816121.git.skhan@linuxfoundation.org>
Date:   Tue, 22 Sep 2020 19:43:34 -0600
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     rafael@...nel.org, lenb@...nel.org, gregkh@...uxfoundation.org,
        keescook@...omium.org
Cc:     Shuah Khan <skhan@...uxfoundation.org>, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [RFC PATCH 05/11] drivers/acpi: convert seqno counter_atomic

counter_atomic is introduced to be used when a variable is used as
a simple counter and doesn't guard object lifetimes. This clearly
differentiates atomic_t usages that guard object lifetimes.

counter_atomic variables will wrap around to 0 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.

Convert it to use counter_atomic.

This conversion doesn't change the oveflow wrap around behavior.

Signed-off-by: Shuah Khan <skhan@...uxfoundation.org>
---
 drivers/acpi/acpi_extlog.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/acpi/acpi_extlog.c b/drivers/acpi/acpi_extlog.c
index f138e12b7b82..23b696b7eb14 100644
--- a/drivers/acpi/acpi_extlog.c
+++ b/drivers/acpi/acpi_extlog.c
@@ -12,6 +12,7 @@
 #include <linux/ratelimit.h>
 #include <linux/edac.h>
 #include <linux/ras.h>
+#include <linux/counters.h>
 #include <asm/cpu.h>
 #include <asm/mce.h>

@@ -93,7 +94,7 @@ static struct acpi_hest_generic_status *extlog_elog_entry_check(int cpu, int ban
 static void __print_extlog_rcd(const char *pfx,
 			       struct acpi_hest_generic_status *estatus, int cpu)
 {
-	static atomic_t seqno;
+	static struct counter_atomic seqno;
 	unsigned int curr_seqno;
 	char pfx_seq[64];

@@ -103,7 +104,7 @@ static void __print_extlog_rcd(const char *pfx,
 		else
 			pfx = KERN_ERR;
 	}
-	curr_seqno = atomic_inc_return(&seqno);
+	curr_seqno = counter_atomic_inc_return(&seqno);
 	snprintf(pfx_seq, sizeof(pfx_seq), "%s{%u}", pfx, curr_seqno);
 	printk("%s""Hardware error detected on CPU%d\n", pfx_seq, cpu);
 	cper_estatus_print(pfx_seq, estatus);
-- 
2.25.1