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    Subject[PATCH AUTOSEL for 4.14 078/100] kmemleak: add scheduling point to kmemleak_scan()
    Date
    From: Yisheng Xie <xieyisheng1@huawei.com>

    [ Upstream commit bde5f6bc68db51128f875a756e9082a6c6ff7b4c ]

    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:

    watchdog: BUG: soft lockup - CPU#53 stuck for 22s! [bash:10287]
    [...]
    Call Trace:
    kmemleak_scan+0x21a/0x4c0
    kmemleak_write+0x312/0x350
    full_proxy_write+0x5a/0xa0
    __vfs_write+0x33/0x150
    vfs_write+0xad/0x1a0
    SyS_write+0x52/0xc0
    do_syscall_64+0x61/0x1a0
    entry_SYSCALL64_slow_path+0x25/0x25

    Fix this by adding cond_resched every MAX_SCAN_SIZE.

    Link: http://lkml.kernel.org/r/1511439788-20099-1-git-send-email-xieyisheng1@huawei.com
    Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>
    Suggested-by: Catalin Marinas <catalin.marinas@arm.com>
    Acked-by: Catalin Marinas <catalin.marinas@arm.com>
    Cc: Michal Hocko <mhocko@kernel.org>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    ---
    mm/kmemleak.c | 2 ++
    1 file changed, 2 insertions(+)

    diff --git a/mm/kmemleak.c b/mm/kmemleak.c
    index 7780cd83a495..a1ba553816eb 100644
    --- a/mm/kmemleak.c
    +++ b/mm/kmemleak.c
    @@ -1532,6 +1532,8 @@ 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();
    --
    2.11.0
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