Am 13.9.2018 18:22, schrieb Chris Murphy:
(resend to all)
On Thu, Sep 13, 2018 at 9:44 AM, Nikolay Borisov <nbori...@suse.com>
wrote:
On 13.09.2018 18:30, Chris Murphy wrote:
This is the 2nd or 3rd thread containing hanging btrfs send, with
kernel 4.18.x. The subject of one is "btrfs send hung in pipe_wait"
and the other I can't find at the moment. In that case though the
hang
is reproducible in 4.14.x and weirdly it only happens when a snapshot
contains (perhaps many) reflinks. Scrub and check lowmem find nothing
wrong.
I have snapshots with a few reflinks (cp --reflink and also
deduplication), and I see maybe 15-30 second hangs where nothing is
apparently happening (in top or iotop), but I'm also not seeing any
blocked tasks or high CPU usage. Perhaps in my case it's just
recovering quickly.
Are there any kernel config options in "# Debug Lockups and Hangs"
that might hint at what's going on? Some of these are enabled in
Fedora debug kernels, which are built practically daily, e.g. right
now the latest in the build system is 4.19.0-0.rc3.git2.1 - which
translates to git 54eda9df17f3.
If it's a lock-related problem then you need Lock Debugging => Lock
debugging: prove locking correctness
OK looks like that's under a different section as CONFIG_PROVE_LOCKING
which is enabled on Fedora debug kernels.
# Debug Lockups and Hangs
CONFIG_LOCKUP_DETECTOR=y
CONFIG_SOFTLOCKUP_DETECTOR=y
# CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC is not set
CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE=0
CONFIG_HARDLOCKUP_DETECTOR_PERF=y
CONFIG_HARDLOCKUP_CHECK_TIMESTAMP=y
CONFIG_HARDLOCKUP_DETECTOR=y
# CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is not set
CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE=0
# Lock Debugging (spinlocks, mutexes, etc...)
CONFIG_LOCK_DEBUGGING_SUPPORT=y
CONFIG_PROVE_LOCKING=y
CONFIG_LOCK_STAT=y
CONFIG_DEBUG_SPINLOCK=y
CONFIG_DEBUG_LOCK_ALLOC=y
CONFIG_LOCKDEP=y
# CONFIG_DEBUG_LOCKDEP is not set
# CONFIG_DEBUG_LOCKING_API_SELFTESTS is not set
CONFIG_LOCK_TORTURE_TEST=m
Hello again!
I have CONFIG_PROVE_LOCKING enabled in my kernel, but no change to
the observed behaviour.
Best regards, Jürgen
--
Jürgen Herrmann
https://t-5.eu
ALbertstraße 2
94327 Bogen
