* [PATCH] kmemcheck: add scheduling point to kmemleak_scan
@ 2017-11-17 7:03 Yisheng Xie
2017-11-17 18:27 ` Catalin Marinas
0 siblings, 1 reply; 3+ messages in thread
From: Yisheng Xie @ 2017-11-17 7:03 UTC (permalink / raw)
To: akpm, catalin.marinas, mhocko; +Cc: linux-mm, linux-kernel
kmemleak_scan will scan struct page for each node and it can be really
large and resulting in a soft lockup. We have seen a soft lockup when do
scan while compile kernel:
[ 220.561051] watchdog: BUG: soft lockup - CPU#53 stuck for 22s! [bash:10287]
[...]
[ 220.753837] Call Trace:
[ 220.756296] kmemleak_scan+0x21a/0x4c0
[ 220.760034] kmemleak_write+0x312/0x350
[ 220.763866] ? do_wp_page+0x147/0x4c0
[ 220.767521] full_proxy_write+0x5a/0xa0
[ 220.771351] __vfs_write+0x33/0x150
[ 220.774833] ? __inode_security_revalidate+0x4c/0x60
[ 220.779782] ? selinux_file_permission+0xda/0x130
[ 220.784479] ? _cond_resched+0x15/0x30
[ 220.788221] vfs_write+0xad/0x1a0
[ 220.791529] SyS_write+0x52/0xc0
[ 220.794758] do_syscall_64+0x61/0x1a0
[ 220.798411] entry_SYSCALL64_slow_path+0x25/0x25
Fix this by adding cond_resched every 1024 pages.
Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>
---
mm/kmemleak.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index e4738d5..e9f2e86 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -1523,6 +1523,8 @@ static void kmemleak_scan(void)
if (page_count(page) == 0)
continue;
scan_block(page, page + 1, NULL);
+ if (!(pfn % 1024))
+ cond_resched();
}
}
put_online_mems();
--
1.7.12.4
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] kmemcheck: add scheduling point to kmemleak_scan
2017-11-17 7:03 [PATCH] kmemcheck: add scheduling point to kmemleak_scan Yisheng Xie
@ 2017-11-17 18:27 ` Catalin Marinas
2017-11-20 9:46 ` Yisheng Xie
0 siblings, 1 reply; 3+ messages in thread
From: Catalin Marinas @ 2017-11-17 18:27 UTC (permalink / raw)
To: Yisheng Xie; +Cc: akpm, mhocko, linux-mm, linux-kernel
Please fix the subject as the tool is called "kmemleak" rather than
"kmemcheck".
On Fri, Nov 17, 2017 at 03:03:56PM +0800, Yisheng Xie wrote:
> diff --git a/mm/kmemleak.c b/mm/kmemleak.c
> index e4738d5..e9f2e86 100644
> --- a/mm/kmemleak.c
> +++ b/mm/kmemleak.c
> @@ -1523,6 +1523,8 @@ static void kmemleak_scan(void)
> if (page_count(page) == 0)
> continue;
> scan_block(page, page + 1, NULL);
> + if (!(pfn % 1024))
> + cond_resched();
For consistency with the other places where we call cond_resched() in
kmemleak, I would use MAX_SCAN_SIZE. Something like
if (!(pfn % (MAX_SCAN_SIZE / sizeof(page))))
cont_resched();
Thanks.
--
Catalin
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] kmemcheck: add scheduling point to kmemleak_scan
2017-11-17 18:27 ` Catalin Marinas
@ 2017-11-20 9:46 ` Yisheng Xie
0 siblings, 0 replies; 3+ messages in thread
From: Yisheng Xie @ 2017-11-20 9:46 UTC (permalink / raw)
To: Catalin Marinas; +Cc: akpm, mhocko, linux-mm, linux-kernel
Hi Catalin,
On 2017/11/18 2:27, Catalin Marinas wrote:
> Please fix the subject as the tool is called "kmemleak" rather than
> "kmemcheck".
Yeah, this really is a terrible typo.
>
> On Fri, Nov 17, 2017 at 03:03:56PM +0800, Yisheng Xie wrote:
>> diff --git a/mm/kmemleak.c b/mm/kmemleak.c
>> index e4738d5..e9f2e86 100644
>> --- a/mm/kmemleak.c
>> +++ b/mm/kmemleak.c
>> @@ -1523,6 +1523,8 @@ static void kmemleak_scan(void)
>> if (page_count(page) == 0)
>> continue;
>> scan_block(page, page + 1, NULL);
>> + if (!(pfn % 1024))
>> + cond_resched();
>
> For consistency with the other places where we call cond_resched() in
> kmemleak, I would use MAX_SCAN_SIZE. Something like
>
> if (!(pfn % (MAX_SCAN_SIZE / sizeof(page))))
> cont_resched();
Yes, this will keep it consistency with the other places.
I will take both of these suggestion in next version.
Thanks
Yisheng Xie
>
> Thanks.
>
^ permalink raw reply [flat|nested] 3+ messages in thread
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2017-11-17 18:27 ` Catalin Marinas
2017-11-20 9:46 ` Yisheng Xie
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