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Subject: Re: [PATCH v3 40/44] SUNRPC: Simplify TCP receive code by switching
 to using iterators
To:     Trond Myklebust <trondmy@hammerspace.com>
Cc:     "catalin.marinas@arm.com" <catalin.marinas@arm.com>,
        "linux-nfs@vger.kernel.org" <linux-nfs@vger.kernel.org>
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From:   Cristian Marussi <cristian.marussi@arm.com>
Message-ID: <a23d0c18-1030-82f3-a046-41497dc7725b@arm.com>
Date:   Fri, 30 Nov 2018 16:19:06 +0000
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Hi

On 29/11/2018 19:56, Trond Myklebust wrote:
> On Thu, 2018-11-29 at 19:28 +0000, Cristian Marussi wrote:
>> Hi Trond, Catalin
[snip]
> 
> Question to you both: when this happens, does /proc/*/stack show any of
> the processes hanging in the socket or sunrpc code? If so, can you
> please send me examples of those stack traces (i.e. the contents of
> /proc/<pid>/stack for the processes that are hanging)

(using a reverse shell since starting ssh causes a lot of pain and traffic)

Looking at NFS traffic holes(30-40 secs) to detect Client side various HANGS
----------------------------------------------------------------------------

root@sqwt-ubuntu:/opt/lkp-tests# nc -lk -e /bin/bash -s 192.168.0.1 -p 1235 &
root@sqwt-ubuntu:/opt/lkp-tests# lkp run ./dbench-100%.yaml

$ nc 192.168.0.1 1235

cat /proc/2833/cmdline
ruby/opt/lkp-tests/bin/run-local./dbench-100%.yaml

HANG CLOSE
----------
cat /proc/2833/stack
[<0>] __switch_to+0x6c/0x90
[<0>] rpc_wait_bit_killable+0x2c/0xb0
[<0>] __rpc_wait_for_completion_task+0x3c/0x48
[<0>] nfs4_do_close+0x1ec/0x2b0
[<0>] __nfs4_close+0x130/0x198
[<0>] nfs4_close_sync+0x34/0x40
[<0>] nfs4_close_context+0x40/0x50
[<0>] __put_nfs_open_context+0xac/0x118
[<0>] nfs_file_clear_open_context+0x38/0x58
[<0>] nfs_file_release+0x7c/0x90
[<0>] __fput+0x94/0x1c0
[<0>] ____fput+0x20/0x30
[<0>] task_work_run+0x98/0xb8
[<0>] do_notify_resume+0x2d0/0x318
[<0>] work_pending+0x8/0x10
[<0>] 0xffffffffffffffff

HANG READ
---------
cat /proc/2833/stack
[<0>] __switch_to+0x6c/0x90
[<0>] io_schedule+0x20/0x40
[<0>] wait_on_page_bit_killable+0x164/0x260
[<0>] generic_file_read_iter+0x1c4/0x820
[<0>] nfs_file_read+0xa4/0x108
[<0>] __vfs_read+0x120/0x170
[<0>] vfs_read+0x94/0x150
[<0>] ksys_read+0x6c/0xd8
[<0>] __arm64_sys_read+0x24/0x30
[<0>] el0_svc_handler+0x7c/0x118
[<0>] el0_svc+0x8/0xc
[<0>] 0xffffffffffffffff


HANG STAT
---------
cat /proc/2833/stack
[<0>] __switch_to+0x6c/0x90
[<0>] rpc_wait_bit_killable+0x2c/0xb0
[<0>] __rpc_execute+0x1cc/0x528
[<0>] rpc_execute+0xe4/0x1b0
[<0>] rpc_run_task+0x130/0x168
[<0>] nfs4_call_sync_sequence+0x80/0xc8
[<0>] _nfs4_proc_getattr+0xc8/0xf8
[<0>] nfs4_proc_getattr+0x88/0x1d8
[<0>] __nfs_revalidate_inode+0x1f8/0x468
[<0>] nfs_getattr+0x14c/0x420
[<0>] vfs_getattr_nosec+0x7c/0x98
[<0>] vfs_getattr+0x48/0x58
[<0>] vfs_statx+0xb4/0x118
[<0>] __se_sys_newfstatat+0x58/0x98
[<0>] __arm64_sys_newfstatat+0x24/0x30
[<0>] el0_svc_handler+0x7c/0x118
[<0>] el0_svc+0x8/0xc
[<0>] 0xffffffffffffffff

....


Looking at a straced lkp to detect HANGS
----------------------------------------

cat /proc/2878/cmdline
ruby/opt/lkp-tests/bin/run-local./dbench-100%.yaml

HANG READ
----------
cat /proc/2878/stack
[<0>] __switch_to+0x6c/0x90
[<0>] io_schedule+0x20/0x40
[<0>] wait_on_page_bit_killable+0x164/0x260
[<0>] generic_file_read_iter+0x1c4/0x820
[<0>] nfs_file_read+0xa4/0x108
[<0>] __vfs_read+0x120/0x170
[<0>] vfs_read+0x94/0x150
[<0>] ksys_read+0x6c/0xd8
[<0>] __arm64_sys_read+0x24/0x30
[<0>] el0_svc_handler+0x7c/0x118
[<0>] el0_svc+0x8/0xc
[<0>] 0xffffffffffffffff

...

cat /proc/2878/status
Name:	ruby
Umask:	0022
State:	D (disk sleep)
Tgid:	2878
Ngid:	0
Pid:	2878
PPid:	2876
TracerPid:	2876
Uid:	0	0	0	0
Gid:	0	0	0	0
FDSize:	64
Groups:	
NStgid:	2878
NSpid:	2878
NSpgid:	2876
NSsid:	2822
VmPeak:	   24192 kB
VmSize:	   24192 kB
VmLck:	       0 kB
VmPin:	       0 kB
VmHWM:	   13376 kB
VmRSS:	   13376 kB
RssAnon:	    8768 kB
RssFile:	    4608 kB
RssShmem:	       0 kB
VmData:	    9792 kB
VmStk:	    8192 kB
VmExe:	      64 kB
VmLib:	    5888 kB
VmPTE:	     320 kB
VmSwap:	       0 kB
HugetlbPages:	       0 kB
CoreDumping:	0
Threads:	2
SigQ:	0/7534
SigPnd:	0000000000000000
ShdPnd:	0000000000000000
SigBlk:	0000000000000000
SigIgn:	0000000000000000
SigCgt:	00000001c2007e4f
CapInh:	0000000000000000
CapPrm:	0000003fffffffff
CapEff:	0000003fffffffff
CapBnd:	0000003fffffffff
CapAmb:	0000000000000000
NoNewPrivs:	0
Seccomp:	0
Speculation_Store_Bypass:	unknown
Cpus_allowed:	3f
Cpus_allowed_list:	0-5
Mems_allowed:	1
Mems_allowed_list:	0
voluntary_ctxt_switches:	7547
nonvoluntary_ctxt_switches:	564


Thanks

Cristian