Douglas Anderson ac31ef00ad kgdb: Avoid suspicious RCU usage warning ... [ Upstream commit 440ab9e10e ] At times when I'm using kgdb I see a splat on my console about suspicious RCU usage. I managed to come up with a case that could reproduce this that looked like this: WARNING: suspicious RCU usage 5.7.0-rc4+ #609 Not tainted ----------------------------- kernel/pid.c:395 find_task_by_pid_ns() needs rcu_read_lock() protection! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 3 locks held by swapper/0/1: #0: ffffff81b6b8e988 (&dev->mutex){....}-{3:3}, at: __device_attach+0x40/0x13c #1: ffffffd01109e9e8 (dbg_master_lock){....}-{2:2}, at: kgdb_cpu_enter+0x20c/0x7ac #2: ffffffd01109ea90 (dbg_slave_lock){....}-{2:2}, at: kgdb_cpu_enter+0x3ec/0x7ac stack backtrace: CPU: 7 PID: 1 Comm: swapper/0 Not tainted 5.7.0-rc4+ #609 Hardware name: Google Cheza (rev3+) (DT) Call trace: dump_backtrace+0x0/0x1b8 show_stack+0x1c/0x24 dump_stack+0xd4/0x134 lockdep_rcu_suspicious+0xf0/0x100 find_task_by_pid_ns+0x5c/0x80 getthread+0x8c/0xb0 gdb_serial_stub+0x9d4/0xd04 kgdb_cpu_enter+0x284/0x7ac kgdb_handle_exception+0x174/0x20c kgdb_brk_fn+0x24/0x30 call_break_hook+0x6c/0x7c brk_handler+0x20/0x5c do_debug_exception+0x1c8/0x22c el1_sync_handler+0x3c/0xe4 el1_sync+0x7c/0x100 rpmh_rsc_probe+0x38/0x420 platform_drv_probe+0x94/0xb4 really_probe+0x134/0x300 driver_probe_device+0x68/0x100 __device_attach_driver+0x90/0xa8 bus_for_each_drv+0x84/0xcc __device_attach+0xb4/0x13c device_initial_probe+0x18/0x20 bus_probe_device+0x38/0x98 device_add+0x38c/0x420 If I understand properly we should just be able to blanket kgdb under one big RCU read lock and the problem should go away. We'll add it to the beast-of-a-function known as kgdb_cpu_enter(). With this I no longer get any splats and things seem to work fine. Signed-off-by: Douglas Anderson <dianders@chromium.org> Link: https://lore.kernel.org/r/20200602154729.v2.1.I70e0d4fd46d5ed2aaf0c98a355e8e1b7a5bb7e4e@changeid Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org> Signed-off-by: Sasha Levin <sashal@kernel.org>		2020-07-09 09:36:30 +02:00
..
bpf	bpf: Explicitly memset some bpf info structures declared on the stack	2020-04-02 16:34:37 +02:00
cgroup	cgroup1: don't call release_agent when it is ""	2020-04-02 16:34:27 +02:00
configs	ANDROID: binder: add hwbinder,vndbinder to BINDER_DEVICES.	2017-08-22 18:43:23 -07:00
debug	kgdb: Avoid suspicious RCU usage warning	2020-07-09 09:36:30 +02:00
events	perf: Add cond_resched() to task_function_call()	2020-06-20 10:25:06 +02:00
gcov	kernel/gcov/fs.c: gcov_seq_next() should increase position index	2020-05-02 17:24:14 +02:00
irq	genirq/generic_pending: Do not lose pending affinity update	2020-06-03 08:18:12 +02:00
livepatch	livepatch: Nullify obj->mod in klp_module_coming()'s error path	2019-10-07 18:55:09 +02:00
locking	locktorture: Print ratio of acquisitions, not failures	2020-04-24 08:01:23 +02:00
power	PM: hibernate: Freeze kernel threads in software_resume()	2020-05-05 19:15:50 +02:00
printk	printk: fix integer overflow in setup_log_buf()	2019-12-01 09:13:17 +01:00
rcu	rcuperf: Fix cleanup path for invalid perf_type strings	2019-05-31 06:47:33 -07:00
sched	sched/core: Fix PI boosting between RT and DEADLINE tasks	2020-06-30 15:38:05 -04:00
time	clocksource: Prevent double add_timer_on() for watchdog_timer	2020-02-14 16:32:20 -05:00
trace	tracing: Fix event trigger to accept redundant spaces	2020-06-30 15:38:08 -04:00
.gitignore
acct.c	kernel/acct.c: fix the acct->needcheck check in check_free_space()	2018-01-10 09:31:17 +01:00
async.c	kernel/async.c: revert "async: simplify lowest_in_progress()"	2018-02-16 20:23:05 +01:00
audit.c	audit: fix a net reference leak in audit_list_rules_send()	2020-06-20 10:25:10 +02:00
audit.h	audit: fix a net reference leak in audit_list_rules_send()	2020-06-20 10:25:10 +02:00
audit_fsnotify.c
audit_tree.c	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
audit_watch.c	audit_get_nd(): don't unlock parent too early	2019-12-17 20:37:27 +01:00
auditfilter.c	audit: fix a net reference leak in audit_list_rules_send()	2020-06-20 10:25:10 +02:00
auditsc.c	audit: print empty EXECVE args	2019-12-01 09:14:03 +01:00
backtracetest.c
bounds.c	kbuild: fix kernel/bounds.c 'W=1' warning	2018-11-13 11:15:08 -08:00
capability.c	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
compat.c	make 'user_access_begin()' do 'access_ok()'	2020-06-20 10:24:58 +02:00
configs.c
context_tracking.c
cpu.c	x86/speculation: Remove redundant arch_smt_update() invocation	2020-04-24 08:00:41 +02:00
cpu_pm.c	kernel/cpu_pm: Fix uninitted local in cpu_pm	2020-06-20 10:25:19 +02:00
crash_core.c	kdump: write correct address of mem_section into vmcoreinfo	2018-01-17 09:45:27 +01:00
crash_dump.c
cred.c	memcg: account security cred as well to kmemcg	2020-01-09 10:17:54 +01:00
delayacct.c	delayacct: Use raw_spinlocks	2018-08-03 07:50:38 +02:00
dma.c	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
elfcore.c	kernel/elfcore.c: include proper prototypes	2019-10-11 18:18:42 +02:00
exec_domain.c	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
exit.c	exit: Move preemption fixup up, move blocking operations down	2020-06-20 10:25:10 +02:00
extable.c	extable: Enable RCU if it is not watching in kernel_text_address()	2017-09-23 16:50:20 -04:00
fork.c	futex: Split futex_mm_release() for exit/exec	2019-12-05 15:38:26 +01:00
freezer.c
futex.c	futex: Unbreak futex hashing	2020-04-02 16:34:21 +02:00
groups.c	kernel: make groups_sort calling a responsibility group_info allocators	2017-12-20 10:10:18 +01:00
hung_task.c	kernel: hung_task.c: disable on suspend	2019-04-20 09:15:05 +02:00
irq_work.c
jump_label.c	sched/core: Fix cpu.max vs. cpuhotplug deadlock	2018-12-05 19:41:17 +01:00
kallsyms.c	kallsyms: Don't let kallsyms_lookup_size_offset() fail on retrieving the first symbol	2019-09-21 07:15:38 +02:00
kcmp.c	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt
kcov.c	kcov: ensure irq code sees a valid area	2018-08-03 07:50:22 +02:00
kexec.c	kdump: protect vmcoreinfo data under the crash memory	2017-07-12 16:26:00 -07:00
kexec_core.c	kexec: Allocate decrypted control pages for kdump if SME is enabled	2019-11-24 08:23:15 +01:00
kexec_file.c	kexec_file: adjust declaration of kexec_purgatory	2017-07-12 16:26:02 -07:00
kexec_internal.h	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
kmod.c	kmod: make request_module() return an error when autoloading is disabled	2020-04-24 08:00:44 +02:00
kprobes.c	kretprobe: Prevent triggering kretprobe from within kprobe_flush_task	2020-06-25 15:42:02 +02:00
ksysfs.c	kexec: move vmcoreinfo out of the kernel's .bss section	2017-07-12 16:25:59 -07:00
kthread.c	kthread, tracing: Don't expose half-written comm when creating kthreads	2018-08-03 07:50:21 +02:00
latencytop.c
Makefile	y2038: futex: Move compat implementation into futex.c	2019-12-05 15:38:22 +01:00
memremap.c	mm, devm_memremap_pages: kill mapping "System RAM" support	2019-01-13 10:01:02 +01:00
module-internal.h
module.c	kernel/module: Fix memleak in module_add_modinfo_attrs()	2020-02-14 16:32:06 -05:00
module_signing.c
notifier.c	x86/mm: split vmalloc_sync_all()	2020-04-02 16:34:20 +02:00
nsproxy.c
padata.c	padata: purge get_cpu and reorder_via_wq from padata_do_serial	2020-05-27 16:43:05 +02:00
panic.c	panic: ensure preemption is disabled during panic()	2019-10-17 13:43:19 -07:00
params.c	kernel/params.c: improve STANDARD_PARAM_DEF readability	2017-10-03 17:54:26 -07:00
pid.c	pids: make task_tgid_nr_ns() safe	2017-08-21 12:47:31 -07:00
pid_namespace.c	signal/pid_namespace: Fix reboot_pid_ns to use send_sig not force_sig	2019-07-31 07:28:21 +02:00
profile.c
ptrace.c	ptrace: reintroduce usage of subjective credentials in ptrace_has_cap()	2020-01-23 08:20:32 +01:00
range.c	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
reboot.c
relay.c	kernel/relay.c: handle alloc_percpu returning NULL in relay_open	2020-06-11 09:22:58 +02:00
resource.c	resource: fix integer overflow at reallocation	2018-04-24 09:36:22 +02:00
seccomp.c	seccomp: Move speculation migitation control to arch code	2018-05-22 18:54:04 +02:00
signal.c	signal: Extend exec_id to 64bits	2020-04-24 08:00:38 +02:00
smp.c	cpu/hotplug: Fix "SMT disabled by BIOS" detection for KVM	2019-02-12 19:46:13 +01:00
smpboot.c	watchdog/core, powerpc: Lock cpus across reconfiguration	2017-10-04 10:53:54 +02:00
smpboot.h	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
softirq.c	Mark HI and TASKLET softirq synchronous	2018-08-15 18:12:47 +02:00
stacktrace.c
stop_machine.c	stop_machine: Atomically queue and wake stopper threads	2018-09-05 09:26:36 +02:00
sys.c	kernel/sys.c: prctl: fix false positive in validate_prctl_map()	2019-06-15 11:54:52 +02:00
sys_ni.c	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
sysctl.c	kernel: sysctl: make drop_caches write-only	2020-01-04 13:59:57 +01:00
sysctl_binary.c	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
task_work.c	locking/barriers: Convert users of lockless_dereference() to READ_ONCE()	2017-12-25 14:26:21 +01:00
taskstats.c	taskstats: fix data-race	2020-01-09 10:17:53 +01:00
test_kprobes.c
torture.c	torture: Fix typo suppressing CPU-hotplug statistics	2017-07-25 13:04:45 -07:00
tracepoint.c	tracepoint: Do not warn on ENOMEM	2018-05-09 09:51:50 +02:00
tsacct.c
ucount.c
uid16.c	kernel: make groups_sort calling a responsibility group_info allocators	2017-12-20 10:10:18 +01:00
umh.c	coredump: fix crash when umh is disabled	2020-05-20 08:16:58 +02:00
up.c	smp: Avoid using two cache lines for struct call_single_data	2017-08-29 15:14:38 +02:00
user-return-notifier.c
user.c
user_namespace.c	userns: move user access out of the mutex	2018-09-09 19:56:00 +02:00
utsname.c
utsname_sysctl.c	sys: don't hold uts_sem while accessing userspace memory	2018-09-09 19:56:00 +02:00
watchdog.c	watchdog/softlockup: Enforce that timestamp is valid on boot	2020-02-28 16:36:05 +01:00
watchdog_hld.c	watchdog: Mark watchdog touch functions as notrace	2018-09-05 09:26:42 +02:00
workqueue.c	workqueue: don't use wq_select_unbound_cpu() for bound works	2020-03-20 10:54:16 +01:00
workqueue_internal.h	Merge branch 'for-4.14-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq	2017-11-06 12:26:49 -08:00