[dm-devel] [QUESTION] multipathd crash when stopping

[lixiaokeng]

When stopping multipathd (systemctl restart multipathd.service), there
is a multipathd crash occasionally(not reproduced).

Here is stack:
#0 __GI_raise (sig=sig at entry=6) at ../sysdeps/unix/sysv/linux/raise.c:51
#1 0x0000ffff87d9e81c in __GI_abort () at abort.c:79
#2 0x0000ffff87dd7818 in __libc_message (action=action at entry=do_abort,
fmt=fmt at entry=0xffff87e97888 "%s\n") at ../sysdeps/posix/libc_fatal.c:181
#3 0x0000ffff87dddf6c in malloc_printerr (
str=str at entry=0xffff87e950d0 "free(): invalid pointer") at malloc.c:5389
#4 0x0000ffff87ddf780 in _int_free (av=0xffff87ed7a58 <main_arena>, p=0xffff80000070,
have_lock=0) at malloc.c:4172
#5 0x0000ffff880f55a8 in internal_hashmap_clear (h=h at entry=0xffff80027980,
default_free_key=, default_free_value=)
at ../src/basic/hashmap.c:902
#6 0x0000ffff880f56a0 in internal_hashmap_free (h=,
default_free_key=, default_free_value=,
default_free_value=, default_free_key=, h=)
at ../src/basic/hashmap.c:874
#7 0x0000ffff880f582c in ordered_hashmap_free_free_free () at ../src/basic/hashmap.h:118
#8 device_free (device=0xffff80027820) at ../src/libsystemd/sd-device/sd-device.c:68
#9 sd_device_unref (p=) at ../src/libsystemd/sd-device/sd-device.c:78
#10 0x0000ffff88100978 in sd_device_unrefp () at ../src/systemd/sd-device.h:118
#11 device_new_from_nulstr (len=, nulstr=0xffff877f93d0 "",
ret=) at ../src/libsystemd/sd-device/device-private.c:448
#12 device_monitor_receive_device (m=0xffff80000b20, ret=ret at entry=0xffff877fb388)
at ../src/libsystemd/sd-device/device-monitor.c:447
#13 0x0000ffff881028a4 in udev_monitor_receive_sd_device (ret=0xffff877fb388,
udev_monitor=0xffff80000c70) at ../src/libudev/libudev-monitor.c:207
#14 udev_monitor_receive_device (udev_monitor=0xffff80000c70,
udev_monitor at entry=0xffff877fb3a0) at ../src/libudev/libudev-monitor.c:253
#15 0x0000ffff881a3478 in uevent_listen (udev=0xffff877fbf40) at uevent.c:853
#16 0x0000aaaadc524514 in ueventloop (ap=0xffffc4134bd0) at main.c:1518
#17 0x0000ffff880827ac in start_thread (arg=0xffff8821e380) at pthread_create.c:486
#18 0x0000ffff87e3c47c in thread_start () at ../sysdeps/unix/sysv/linux/aarch64/clone.S:78

There's a strange phenomenon here.
In frame 11, nulstr=0xffff877f93d0 "". But in frame 12,
x/32bs (uint8_t*) &buf.raw[bufpos]
0xffff877f9360: "ACTION"
0xffff877f9367: "change"
0xffff877f936e: "DEVPATH"
0xffff877f9376: "/devices/virtual/block/dm-69"
0xffff877f9393: "SUBSYSTEM"
0xffff877f939d: "block"
0xffff877f93a3: "DM_COOKIE"
0xffff877f93ad: "23068672"
0xffff877f93b6: "DEVNAME"
0xffff877f93be: "/dev/dm-69"
0xffff877f93c9: "DEVTYPE"
0xffff877f93d1: "disk"
0xffff877f93d6: "SEQNUM"
0xffff877f93dd: "14437"
0xffff877f93e3: "USEC_INITIALIZED"
0xffff877f93f4: "8213096220"
0xffff877f93ff: "MAJOR"
0xffff877f9405: "253"
0xffff877f9409: "MINOR"
0xffff877f940f: "69"
0xffff877f9412: "DM_UDEV_DISABLE_LIBRARY_FALLBACK_FLAG"
0xffff877f9438: "1"
0xffff877f943a: "DM_UDEV_PRIMARY_SOURCE_FLAG"
0xffff877f9456: "1"
0xffff877f9458: "DM_SUBSYSTEM_UDEV_FLAG0"
0xffff877f9470: "1"
0xffff877f9472: "DM_ACTIVATION"
0xffff877f9480: "0"
0xffff877f9482: "DM_NAME"
0xffff877f948a: "36e02861100592fcc99ad3c3800000195"
0xffff877f94ac: "DM_UUID"
0xffff877f94b4: "mpath-36e02861100592fcc99ad3c3800000195"

The udev API is suspected at first. However, hashmap is a common data
structure of systemd. Systemd has never had the same call stack.
Can someone help me?