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Subject[PATCH v2] kmemleak: add scheduling point to kmemleak_scan
Date
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 MAX_SCAN_SIZE.

Suggested-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>
---
v2:
* call cond_resched() every MAX_SCAN_SIZE for consistency with the other places
* fix the subject of the patch. - Both per Catalin

mm/kmemleak.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index e4738d5..3d47817 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 % (MAX_SCAN_SIZE / sizeof(*page))))
+ cond_resched();
}
}
put_online_mems();
--
1.7.12.4
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