[PATCH v2] X86 architecture (32-bit and 64-bit): Convert to use jiffies macro

[PATCH v2] X86 architecture (32-bit and 64-bit): Convert to use jiffies macro

[Chen Yufan]

Use time_after macro instead of using
jiffies directly to handle wraparound.

Signed-off-by: Chen Yufan <chenyufan@vivo.com>

The modifications made compared to the previous version are as follows:
1. Remove extra '+' in the header.
---
 arch/x86/kernel/cpu/aperfmperf.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/aperfmperf.c b/arch/x86/kernel/cpu/aperfmperf.c
index 0b69bfbf3..5fe0a7576 100644
--- a/arch/x86/kernel/cpu/aperfmperf.c
+++ b/arch/x86/kernel/cpu/aperfmperf.c
@@ -16,6 +16,7 @@
 #include <linux/sched/topology.h>
 #include <linux/smp.h>
 #include <linux/syscore_ops.h>
+#include <linux/jiffies.h>
 
 #include <asm/cpu.h>
 #include <asm/cpu_device_id.h>
@@ -434,7 +435,7 @@ unsigned int arch_freq_get_on_cpu(int cpu)
 	 * Bail on invalid count and when the last update was too long ago,
 	 * which covers idle and NOHZ full CPUs.
 	 */
-	if (!mcnt || (jiffies - last) > MAX_SAMPLE_AGE)
+	if (!mcnt || time_after(jiffies, last + MAX_SAMPLE_AGE))
 		goto fallback;
 
 	return div64_u64((cpu_khz * acnt), mcnt);
-- 
2.39.0

Re: [PATCH v2] X86 architecture (32-bit and 64-bit): Convert to use jiffies macro

[Thomas Gleixner]

On Thu, Aug 22 2024 at 16:24, Chen Yufan wrote:
> Use time_after macro instead of using
> jiffies directly to handle wraparound.
>
> Signed-off-by: Chen Yufan <chenyufan@vivo.com>
>
> The modifications made compared to the previous version are as follows:

Please put such version information below the --- separator so tools can
strip it off when applying the patch, which avoids editiong

> 1. Remove extra '+' in the header.

The subject line still has a incorrect subsystem prefix:

https://www.kernel.org/doc/html/latest/process/maintainer-tip.html#patch-subject

Also 'use jiffies macro' is not really informative. Something like

     "Use time_after() for jiffies comparison"

makes it entirely clear what this is about.

> Use time_after macro instead of using
> jiffies directly to handle wraparound.

Also here instead of 'time_after macro' please use simply
'time_after()'. It's uninteresting whether this is a macro or not.

Thanks,

        tglx