[linux-next][ppc] kernel hung when running trinity fuzzer

[Kirill Tkhai]

On 28.08.2017 13:28, Abdul Haleem wrote:
> Hi,
> 
> offlate we are seeing hung task call traces when running trinity fuzzer
> test. kernel go hung and requires machine reboot.
> 
> Machine Type : Power 8
> Kernel : 4.13.0-rc6-next-20170825
> config: Tul-VM-config
> 
> 
> call traces:
> -------------
> INFO: task systemd-timesyn:472 blocked for more than 120 seconds.
>       Not tainted 4.13.0-rc6-next-20170825 #3
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this
> message.
> systemd-timesyn D    0   472      1 0x00040000   
> Call Trace:
> [c000000775f2b750] [0000000b00000000] 0xb00000000 (unreliable)
> [c000000775f2b920] [c00000000001c788] __switch_to+0x2a8/0x470
> [c000000775f2b980] [c000000000c16974] __schedule+0x394/0xa40
> [c000000775f2ba50] [c000000000c17068] schedule+0x48/0xc0
> [c000000775f2ba80] [c000000000c1b2e8] rwsem_down_read_failed+0x128/0x1b0
> [c000000775f2bae0] [c0000000001700c8] __percpu_down_read+0x108/0x110
> [c000000775f2bb10] [c00000000038fda8] __sb_start_write+0x118/0x130
> [c000000775f2bb50] [c0000000003c1768] mnt_want_write+0x38/0x80
> [c000000775f2bb80] [c0000000003a3328] path_openat+0x9c8/0x14b0
> [c000000775f2bc90] [c0000000003a579c] do_filp_open+0xfc/0x170
> [c000000775f2bdc0] [c000000000388618] do_sys_open+0x1b8/0x2e0
> [c000000775f2be30] [c00000000000b184] system_call+0x58/0x6c
> INFO: task rs:main Q:Reg:624 blocked for more than 120 seconds.
>       Not tainted 4.13.0-rc6-next-20170825 #3

I'm in CC here, but it doesn't seem my commit 83ced169d9a0 "locking/rwsem-xadd:
Add killable versions of rwsem_down_read_failed()" is involved.

It introduces the code, which is unused at the moment:

kirill$:~/linux-next$ git grep rwsem_down_read_failed_killable
include/linux/rwsem.h:extern struct rw_semaphore *rwsem_down_read_failed_killable(struct rw_semaphore *sem);
kernel/locking/rwsem-xadd.c:rwsem_down_read_failed_killable(struct rw_semaphore *sem)
kernel/locking/rwsem-xadd.c:EXPORT_SYMBOL(rwsem_down_read_failed_killable);

We still call rwsem_down_read_failed() with TASK_UNINTERRUPTIBLE argument, so "signal_pending_state()" branch
is always dead.