[+CC's]
On 06/02/2016 03:48 AM, Sergey Senozhatsky wrote:
On (06/01/16 13:11), Stephen Rothwell wrote:
Hi all,
Changes since 20160531:
My fixes tree contains:
of: silence warnings due to max() usage
The arm tree gained a conflict against Linus' tree.
Non-merge commits (relative to Linus' tree): 1100
936 files changed, 38159 insertions(+), 17475 deletions(-)
Hello,
the cc1 process ended up in DN state during kernel -j4 compilation.
...
[ 2856.323052] INFO: task cc1:4582 blocked for more than 21 seconds.
[ 2856.323055] Not tainted 4.7.0-rc1-next-20160601-dbg-00012-g52c180e-dirty #453
[ 2856.323056] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 2856.323059] cc1 D ffff880057e9fd78 0 4582 4575 0x00000000
[ 2856.323062] ffff880057e9fd78 ffff880057e08000 ffff880057e9fd90 ffff880057ea0000
[ 2856.323065] ffff88005dc3dc68 ffffffff00000001 ffff880057e09500 ffff88005dc3dc80
[ 2856.323067] ffff880057e9fd90 ffffffff81441e33 ffff88005dc3dc68 ffff880057e9fe00
[ 2856.323068] Call Trace:
[ 2856.323074] [<ffffffff81441e33>] schedule+0x83/0x98
[ 2856.323077] [<ffffffff81443d9b>] rwsem_down_write_failed+0x18e/0x1d3
[ 2856.323080] [<ffffffff810a87cf>] ? unlock_page+0x2b/0x2d
[ 2856.323083] [<ffffffff811bdb77>] call_rwsem_down_write_failed+0x17/0x30
[ 2856.323084] [<ffffffff811bdb77>] ? call_rwsem_down_write_failed+0x17/0x30
[ 2856.323086] [<ffffffff81443630>] down_write+0x1f/0x2e
[ 2856.323089] [<ffffffff810ea4f3>] __khugepaged_exit+0x104/0x11a
[ 2856.323091] [<ffffffff8103702a>] mmput+0x29/0xc5
[ 2856.323093] [<ffffffff8103bbd8>] do_exit+0x34c/0x894
[ 2856.323095] [<ffffffff8102f9e0>] ? __do_page_fault+0x2f7/0x399
[ 2856.323097] [<ffffffff8103c188>] do_group_exit+0x3c/0x98
[ 2856.323099] [<ffffffff8103c1f3>] SyS_exit_group+0xf/0xf
[ 2856.323101] [<ffffffff81444cdb>] entry_SYSCALL_64_fastpath+0x13/0x8f
[ 2877.322853] INFO: task cc1:4582 blocked for more than 21 seconds.
[ 2877.322858] Not tainted 4.7.0-rc1-next-20160601-dbg-00012-g52c180e-dirty #453
[ 2877.322858] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 2877.322861] cc1 D ffff880057e9fd78 0 4582 4575 0x00000000
[ 2877.322865] ffff880057e9fd78 ffff880057e08000 ffff880057e9fd90 ffff880057ea0000
[ 2877.322867] ffff88005dc3dc68 ffffffff00000001 ffff880057e09500 ffff88005dc3dc80
[ 2877.322867] ffff880057e9fd90 ffffffff81441e33 ffff88005dc3dc68 ffff880057e9fe00
[ 2877.322870] Call Trace:
[ 2877.322875] [<ffffffff81441e33>] schedule+0x83/0x98
[ 2877.322878] [<ffffffff81443d9b>] rwsem_down_write_failed+0x18e/0x1d3
[ 2877.322881] [<ffffffff810a87cf>] ? unlock_page+0x2b/0x2d
[ 2877.322884] [<ffffffff811bdb77>] call_rwsem_down_write_failed+0x17/0x30
[ 2877.322885] [<ffffffff811bdb77>] ? call_rwsem_down_write_failed+0x17/0x30
[ 2877.322887] [<ffffffff81443630>] down_write+0x1f/0x2e
[ 2877.322890] [<ffffffff810ea4f3>] __khugepaged_exit+0x104/0x11a
[ 2877.322892] [<ffffffff8103702a>] mmput+0x29/0xc5
[ 2877.322894] [<ffffffff8103bbd8>] do_exit+0x34c/0x894
[ 2877.322896] [<ffffffff8102f9e0>] ? __do_page_fault+0x2f7/0x399
[ 2877.322898] [<ffffffff8103c188>] do_group_exit+0x3c/0x98
[ 2877.322900] [<ffffffff8103c1f3>] SyS_exit_group+0xf/0xf
[ 2877.322902] [<ffffffff81444cdb>] entry_SYSCALL_64_fastpath+0x13/0x8f
I think it's this patch:
http://ozlabs.org/~akpm/mmots/broken-out/mm-thp-make-swapin-readahead-under-down_read-of-mmap_sem.patch
Some parts of the code in collapse_huge_page() that were under
down_write(mmap_sem) are under down_read() after the patch. But there's
"goto out" which continues via "goto out_up_write" which does
up_write(mmap_sem) so there's an imbalance. One path seems to go via
both up_read() and up_write(). I can imagine this can cause a stuck
down_write() among other things?
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