linux-kernel - Re: [PATCH] drm/amdkfd: use time_is_before_jiffies(a + b) to replace "jiffies

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Message-ID: <69adb14d-9f70-b118-14b2-92de75596c38@nfschina.com>
Date:   Thu, 28 Jul 2022 10:20:28 +0800
From:   Yu Zhe <yuzhe@...china.com>
To:     Felix Kuehling <felix.kuehling@....com>, alexander.deucher@....com,
        christian.koenig@....com, Xinhui.Pan@....com, airlied@...ux.ie,
        daniel@...ll.ch
Cc:     amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
        liqiong@...china.com
Subject: Re: [PATCH] drm/amdkfd: use time_is_before_jiffies(a + b) to replace
 "jiffies - a > b"

在 2022年07月28日 00:04, Felix Kuehling 写道:

> This patch introduces a build warning for me:
>    CC [M]  drivers/gpu/drm/amd/amdgpu/../amdkfd/kfd_interrupt.o
> In file included from /home/fkuehlin/compute/kernel/include/linux/spinlock.h:54,
>                   from /home/fkuehlin/compute/kernel/include/linux/mmzone.h:8,
>                   from /home/fkuehlin/compute/kernel/include/linux/gfp.h:6,
>                   from /home/fkuehlin/compute/kernel/include/linux/slab.h:15,
>                   from /home/fkuehlin/compute/kernel/drivers/gpu/drm/amd/amdgpu/../amdkfd/kfd_interrupt.c:44:
> /home/fkuehlin/compute/kernel/drivers/gpu/drm/amd/amdgpu/../amdkfd/kfd_interrupt.c: In function ?interrupt_wq?:
> /home/fkuehlin/compute/kernel/include/linux/typecheck.h:12:18: warning: comparison of distinct pointer types lacks a cast
>     12 |  (void)(&__dummy == &__dummy2); \
>        |                  ^~
> /home/fkuehlin/compute/kernel/include/linux/jiffies.h:106:3: note: in expansion of macro ?typecheck?
>    106 |   typecheck(unsigned long, b) && \
>        |   ^~~~~~~~~
> /home/fkuehlin/compute/kernel/include/linux/jiffies.h:154:35: note: in expansion of macro ?time_after?
>    154 | #define time_is_before_jiffies(a) time_after(jiffies, a)
>        |                                   ^~~~~~~~~~
> /home/fkuehlin/compute/kernel/drivers/gpu/drm/amd/amdgpu/../amdkfd/kfd_interrupt.c:159:7: note: in expansion of macro ?time_is_before_jiffies?
>    159 |   if (time_is_before_jiffies(start_jiffies + HZ)) {
>        |       ^~~~~~~~~~~~~~~~~~~~~~
> I think you need to change the the definition of start_jiffies to be
> unsigned long. Do you want to submit a v2 of your patch?

Yes, I will submit v2 patch later.

> That said, I think the existing code was fine, though the type-mismatch
> highlighted by your patch is a bit iffy.

And if the timer wrap changes in the future you won't have to alter your driver code. So I think it's better.

> Regards,
>    Felix
> Am 2022-07-26 um 22:59 schrieb Yu Zhe:
>> time_is_before_jiffies deals with timer wrapping correctly.
>> Signed-off-by: Yu Zhe <yuzhe@...china.com>
>> ---
>>    drivers/gpu/drm/amd/amdkfd/kfd_interrupt.c | 2 +-
>>    1 file changed, 1 insertion(+), 1 deletion(-)
>> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_interrupt.c b/drivers/gpu/drm/amd/amdkfd/kfd_interrupt.c
>> index a9466d154395..6397926e059c 100644
>> --- a/drivers/gpu/drm/amd/amdkfd/kfd_interrupt.c
>> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_interrupt.c
>> @@ -156,7 +156,7 @@ static void interrupt_wq(struct work_struct *work)
>>        while (dequeue_ih_ring_entry(dev, ih_ring_entry)) {
>>            dev->device_info.event_interrupt_class->interrupt_wq(dev,
>>                                    ih_ring_entry);
>> -        if (jiffies - start_jiffies > HZ) {
>> +        if (time_is_before_jiffies(start_jiffies + HZ)) {
>>                /* If we spent more than a second processing signals,
>>                 * reschedule the worker to avoid soft-lockup warnings
>>                 */
>