A zombie setsid process occurs when adb shell setsid <command> is
issued, however llkd can only detect if it is a result of a kernel
livelock by killing the associated parent, which would be adbd;
resulting in the adb connection(s) being terminated. Will special
case this condition in order to preserve adbd for debugging purposes.
We parse <parent>&<child> in ro.llk.blacklist.parent as this
association, thus adbd&[setsid] covers this special case.
Ampersand was selected because it is never part of a process name,
however a setprop in the shell requires it to be escaped or quoted;
init rc file where this is normally specified does not have issue.
getComm() is effectively pure, so hold on to the return value for
sake of efficiency.
This also reverts commit 599958d114
which granted adbd blanket parent immunity from monitoring on
userdebug builds. The new logic is a more refined means of
preserving the live lock checking associated with adbd and allows
the operation to be performed on user builds.
POC: date ; adb shell setsid sleep 900 ; date
Positive for bug, reports less than 15 minutes, otherwise solved.
Test: llkd_unit_test
Bug: 120983740
Change-Id: I6442463a48499d925a3a074423a24a1622905559
Because of the limited length of properties, and to ease the
complexity of product and vendor adjustments, the comma separated
list properties will use a leading comma to preserve the defaults
and add or subtract entries with + and - prefixes respectively.
Without the leading comma, the list is explicitly specified as before.
Cleanup:
- use empty() instead of space() == 0 (or converse if != 0)
- if (unlikely) pprocp can not be allocated, to a to_string(ppid) check
For testing, observe before and after llkd_unit_test below to
confirm leading comma effects for example:
livelock: ro.llk.stack=wait_on_page_bit_killable,bit_wait_io,\
__get_user_pages,cma_alloc
livelock: ro.llk.stack=...,SyS_openat,...
Test: llkd_unit_test
Bug: 120983740
Change-Id: Ia3d164c2fdac5295a474c6c1294a34e4ae9d0b61
User process in S state blocked by deadlock in I/O system
wait_on_page_bit is covered by regular D state tracking.
Bug: 120776455
Test: long term stability on multiple devices
Change-Id: Icdb99b8095f384cb440f0f2bdeba86c5991b9ef4
If an errant process is identified, and the parent is adbd,
on userdebug builds bypass monitoring the process.
Test: unit tests
Bug: 120983740
Change-Id: I2af0797504326b0e95aa4377918b35d17716a6a2
Allow sysrq stack trace dump to be disabled by ro.llk.sysrq_t.
Default is true if not on a limited memory device ro.config.low_ram.
Value is true if the property value is "eng" and on a userdebug or
eng device, signaled by the ro.debuggable set to 1.
Test: compile
Bug: 118712403
Change-Id: I02e999dc640125b6a08dca10077716e5d006da49
This will discover if the I/O is starved.
Add the ability to search for " <symbol>.cfi+0x".
Cleaned up README.md to reflect current defaults.
Test: none
Bug: 113648929
Change-Id: I990a54f99de536406fd752a490e60f962380d71a
Add ro.llk.stack to list a set of symbols that should rarely happen
but if persistent in multiple checks, indicates a live lock condition.
At ro.llk.stack.timeout_ms the process is sent a kill, if it remains,
then panic the kernel.
There is no ABA detection in the paths, the condition for the
stack symbol being present instantaneously must be its rarity of
being caught. If a livelock occurs in the path of the symbol, then
it is possible more than one path could be stuck in the state, but
the best candidate symbols are found underneath a lock resulting in
only one process being the culprit, and the best aim. There may be
processes that induce a look of persistence, if so the symbol is not
a candidate for checking.
Adding cma_alloc to the default list. It is not behind a lock, so
multiple references can happen. The hope is the first one to spin or
wait gets the kill, but there is the possibility that both will get
the kill. It is unknown if this will escalate to a kernel panic at
this time. It is also suspect that a RT task could cause this by
starving the background worker, and llkd could suffer a similar fate
as it is SCHED_BATCH policy.
Test: compile
Bug: 33808187
Bug: 111910505
Bug: 80502612
Change-Id: I49c9f0646d627869144c5c1ca32272515ed60f7b
Add ro.llk.stack to list a set of symbols that should rarely happen
but if persistent in multiple checks, indicates a live lock condition.
At ro.llk.stack.timeout_ms the process is sent a kill, if it remains,
then panic the kernel.
There is no ABA detection in the paths, the condition for the
stack symbol being present instantaneously must be its rarity of
being caught. If a livelock occurs in the path of the symbol, then
it is possible more than one path could be stuck in the state, but
the best candidate symbols are found underneath a lock resulting in
only one process being the culprit, and the best aim. There may be
processes that induce a look of persistence, if so the symbol is not
a candidate for checking.
The current candidate is __get_user_pages, after mm is locked,
should be a very short reference to look up a page, but can be
longer term if starved, or a condition causes a conflicting loop.
Test: compile
Bug: 33808187
Change-Id: I946e85641e59229b7491e929fcab5f1240794254
Feature outlined here is only available on userdebug or eng builds.
Blocked for security reasons because requires ptrace capabilities.
Add ro.llk.stack to list a set of symbols that should rarely happen
but if persistent in multiple checks, indicates a live lock condition.
At ro.llk.stack.timeout_ms the process is sent a kill, if it remains,
then panic the kernel.
There is no ABA detection in the paths, the condition for the
stack symbol being present instantaneously must be its rarity of
being caught. If a livelock occurs in the path of the symbol, then
it is possible more than one path could be stuck in the state, but
the best candidate symbols are found underneath a lock resulting in
only one process being the culprit, and the best aim. There may be
processes that induce a look of persistence, if so the symbol is not
a candidate for checking.
Add ro.llk.blacklist.process.stack to list process names we want
to skip checking. This configuration parameter is also used to
prevent sepolicy noise when trying to acquire stacks from non
ptrace'able services.
Test: gTest llkd_unit_tests
Bug: 33808187
Bug: 111910505
Bug: 80502612
Change-Id: Ie71221e371b189bbdda2a1155d47826997842dcc
Add "false" as an option fed into llkSplit to be equivalent to empty,
as a truly empty list is replaced with the internal defaults. Ensure
that no empty entries are added to the returned list. Add some
additional provisos to README.md, as well as the explanation of what
"false" means for the associated properties.
Test: llkd_unit_test
Bug: 33808187
Bug: 111910505
Bug: 80502612
Change-Id: Iac0457ea1f6cd559b0875f9871dbae839001276d
Report kernel_panic,sysrq,livelock,<state> reboot reason via last
dmesg (pstore console). Add ro.llk.killtest property, which will
allow reliable ABA platforms to drop kill test and go directly
to kernel panic. This should also allow some manual unit testing
of the canonical boot reason report.
New canonical boot reasons from llkd are:
- kernel_panic,sysrq,livelock,alarm llkd itself locked up (Hail Mary)
- kernel_panic,sysrq,livelock,driver uninterrruptible D state
- kernel_panic,sysrq,livelock,zombie uninterrruptible Z state
Manual test assumptions:
- llkd is built by the platform and landed on system partition
- unit test is built and landed in /data/nativetest (could
land in /data/nativetest64, adjust test correspondingly)
- llkd not enabled, ro.llk.enable and ro.llk.killtest
are not set by platform allowing test to adjust all the
configuration properties and start llkd.
- or, llkd is enabled, ro.llk.enable is true, and killtest is
disabled, ro.llk.killtest is false, setup by the platform.
This breaks the go/apct generic operations of the unit test
for llk.zombie and llk.driver as kernel panic results
requiring manual intervention otherwise. If test moves to
go/apct, then we will be forced to bypass these tests under
this condition (but allow them to run if ro.llk.killtest
is "off" so specific testing above/below can be run).
for i in driver zombie; do
adb shell su root setprop ro.llk.killtest off
adb shell /data/nativetest/llkd_unit_test/llkd_unit_test --gtest_filter=llkd.${i}
adb wait-for-device
adb shell su root setprop ro.llk.killtest off
sleep 60
adb shell getprop sys.boot.reason
adb shell /data/nativetest/llkd_unit_test/llkd_unit_test --gtest_filter=llkd.${i}
done
Test: llkd_unit_test (see test assumptions)
Bug: 33808187
Bug: 72838192
Change-Id: I2b24875376ddfdbc282ba3da5c5b3567de85dbc0
If LLK_ENABLE_DEFAULT is false, then check "ro.llk.enable" for "eng",
also the default value if not set, and then check if userdebug build
to establish a default of true for enable. Same for
ro.khungtask.enable.
Test: llkd_unit_test report eng status on "userdebug" or "user" builds
Bug: 33808187
Bug: 72838192
Change-Id: I2adb23c7629dccaa2856c50bccbf4e363703c82c
Introduce a standalone live-lock daemon (llkd), to catch kernel
or native user space deadlocks and take mitigating actions. Will
also configure [khungtaskd] to fortify the actions.
If a thread is in D or Z state with no forward progress for longer
than ro.llk.timeout_ms, or ro.llk.[D|Z].timeout_ms, kill the process
or parent process respectively. If another scan shows the same
process continues to exist, then have a confirmed live-lock condition
and need to panic. Panic the kernel in a manner to provide the
greatest bugreporting details as to the condition. Add a alarm self
watchdog should llkd ever get locked up that is double the expected
time to flow through the mainloop. Sampling is every
ro.llk_sample_ms.
Default will not monitor init, or [kthreadd] and all that [kthreadd]
spawns. This reduces the effectiveness of llkd by limiting its
coverage. If in the future, if value in covering kthreadd spawned
threads, the requirement will be to code drivers so that they do not
remain in a persistent 'D' state, or that they have mechanisms to
recover the thread should it be killed externally. Then the
blacklists can be adjusted accordingly if these conditions are met.
An accompanying gTest set have been added, and will setup a persistent
D or Z process, with and without forward progress, but not in a
live-lock state because that would require a buggy kernel, or a module
or kernel modification to stimulate.
Android Properties llkd respond to (*_ms parms are in milliseconds):
- ro.config.low_ram default false, if true do not sysrq t (dump
all threads).
- ro.llk.enable default false, allow live-lock daemon to be enabled.
- ro.khungtask.enable default false, allow [khungtaskd] to be enabled.
- ro.llk.mlockall default true, allow mlock'd live-lock daemon.
- ro.khungtask.timeout default 12 minutes.
- ro.llk.timeout_ms default 10 minutes, D or Z maximum timelimit,
double this value and it sets the alarm watchdog for llkd.
- ro.llk.D.timeout_ms default ro.llk.timeout_ms, D maximum timelimit.
- ro.llk.Z.timeout_ms default ro.llk.timeout_ms, Z maximum timelimit.
- ro.llk.check_ms default 2 minutes sampling interval
(ro.llk.timeout_ms / 5) for threads in D or Z state.
- ro.llk.blacklist.process default 0,1,2 (kernel, init and
[kthreadd]), and process names (/comm or /cmdline) init,[kthreadd],
lmkd,lmkd.llkd,llkd,[khungtaskd],watchdogd,[watchdogd],
[watchdogd/0] ...
- ro.llk.blacklist.parent default 0,2 (kernel and [kthreadd]) and
"[kthreadd]". A comma separated lists of process ids, /comm names
or /cmdline names.
- ro.llk.blacklist.uid default <empty>, comma separated list of
uid numbers or names from getpwuid/getpwnam.
Test: llkd_unit_test
Bug: 33808187
Bug: 72838192
Change-Id: I32e8aa78aef10834e093265d0f3ed5b4199807c6
