Linus Torvalds 00845eb968 sched: don't cause task state changes in nested sleep debugging ... Commit 8eb23b9f35 ("sched: Debug nested sleeps") added code to report on nested sleep conditions, which we generally want to avoid because the inner sleeping operation can re-set the thread state to TASK_RUNNING, but that will then cause the outer sleep loop not actually sleep when it calls schedule. However, that's actually valid traditional behavior, with the inner sleep being some fairly rare case (like taking a sleeping lock that normally doesn't actually need to sleep). And the debug code would actually change the state of the task to TASK_RUNNING internally, which makes that kind of traditional and working code not work at all, because now the nested sleep doesn't just sometimes cause the outer one to not block, but will cause it to happen every time. In particular, it will cause the cardbus kernel daemon (pccardd) to basically busy-loop doing scheduling, converting a laptop into a heater, as reported by Bruno Prémont. But there may be other legacy uses of that nested sleep model in other drivers that are also likely to never get converted to the new model. This fixes both cases: - don't set TASK_RUNNING when the nested condition happens (note: even if WARN_ONCE() only _warns_ once, the return value isn't whether the warning happened, but whether the condition for the warning was true. So despite the warning only happening once, the "if (WARN_ON(..))" would trigger for every nested sleep. - in the cases where we knowingly disable the warning by using "sched_annotate_sleep()", don't change the task state (that is used for all core scheduling decisions), instead use '->task_state_change' that is used for the debugging decision itself. (Credit for the second part of the fix goes to Oleg Nesterov: "Can't we avoid this subtle change in behaviour DEBUG_ATOMIC_SLEEP adds?" with the suggested change to use 'task_state_change' as part of the test) Reported-and-bisected-by: Bruno Prémont <bonbons@linux-vserver.org> Tested-by: Rafael J Wysocki <rjw@rjwysocki.net> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de>, Cc: Ilya Dryomov <ilya.dryomov@inktank.com>, Cc: Mike Galbraith <umgwanakikbuti@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Hurley <peter@hurleysoftware.com>, Cc: Davidlohr Bueso <dave@stgolabs.net>, Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2015-02-01 12:23:32 -08:00
..
bpf	Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net	2015-01-27 13:55:36 -08:00
configs
debug	Surprising number of fixes this merge window :(	2015-01-23 06:40:36 +12:00
events	perf: Tighten (and fix) the grouping condition	2015-01-28 13:17:35 +01:00
gcov	gcov: enable GCOV_PROFILE_ALL from ARCH Kconfigs	2014-12-13 12:42:51 -08:00
irq	genirq: Prevent proc race against freeing of irq descriptors	2014-12-13 13:33:07 +01:00
locking	mutex: Always clear owner field upon mutex_unlock()	2015-01-09 11:20:39 +01:00
power	PM: Eliminate CONFIG_PM_RUNTIME	2014-12-19 22:55:06 +01:00
printk	This code is a fork from the trace-3.19 pull as it needed the trace_seq	2014-12-13 14:04:41 -08:00
rcu
sched	sched: don't cause task state changes in nested sleep debugging	2015-02-01 12:23:32 -08:00
time	Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2015-01-25 17:47:34 -08:00
trace	This holds a few fixes to the ftrace infrastructure as well as	2015-01-17 07:55:52 +13:00
.gitignore
acct.c
async.c
audit_tree.c	fsnotify: unify inode and mount marks handling	2014-12-13 12:42:53 -08:00
audit_watch.c
audit.c	Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net	2014-12-30 10:45:47 -08:00
audit.h
auditfilter.c	Merge branch 'upstream' of git://git.infradead.org/users/pcmoore/audit	2014-12-23 18:13:16 -08:00
auditsc.c	Merge branch 'upstream' of git://git.infradead.org/users/pcmoore/audit	2014-12-31 14:52:18 -08:00
backtracetest.c
bounds.c
capability.c
cgroup_freezer.c
cgroup.c	cgroup: prevent mount hang due to memory controller lifetime	2015-01-22 10:26:43 -05:00
compat.c
configs.c
context_tracking.c
cpu_pm.c
cpu.c
cpuset.c	Merge branch 'for-3.19' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup	2014-12-11 18:57:19 -08:00
crash_dump.c
cred.c
delayacct.c
dma.c
elfcore.c
exec_domain.c
exit.c	exit: fix race between wait_consider_task() and wait_task_zombie()	2015-01-08 15:10:51 -08:00
extable.c
fork.c	mm: use new helper functions around the i_mmap_mutex	2014-12-13 12:42:45 -08:00
freezer.c
futex_compat.c
futex.c
groups.c
hung_task.c
irq_work.c
jump_label.c
kallsyms.c
kcmp.c
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt
kexec.c	kexec: remove unnecessary KERN_ERR from kexec.c	2014-12-13 12:42:51 -08:00
kmod.c
kprobes.c	module: remove mod arg from module_free, rename module_memfree().	2015-01-20 11:38:33 +10:30
ksysfs.c
kthread.c
latencytop.c
Makefile
module_signing.c
module-internal.h
module.c	module: make module_refcount() a signed integer.	2015-01-22 11:15:54 +10:30
notifier.c
nsproxy.c
padata.c
panic.c
params.c	param: fix uninitialized read with CONFIG_DEBUG_LOCK_ALLOC	2015-01-20 11:38:31 +10:30
pid_namespace.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs	2014-12-16 15:53:03 -08:00
pid.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs	2014-12-16 15:53:03 -08:00
profile.c
ptrace.c
range.c	kernel: avoid overflow in cmp_range	2015-01-17 10:02:23 +13:00
reboot.c
relay.c
resource.c
seccomp.c
signal.c
smp.c
smpboot.c
smpboot.h
softirq.c
stacktrace.c	stacktrace: introduce snprint_stack_trace for buffer output	2014-12-13 12:42:48 -08:00
stop_machine.c
sys_ni.c	syscalls: implement execveat() system call	2014-12-13 12:42:51 -08:00
sys.c	x86, mpx: Strictly enforce empty prctl() args	2015-01-22 21:11:06 +01:00
sysctl_binary.c
sysctl.c	As the merge window is still open, and this code was not as complex	2014-12-16 12:53:59 -08:00
system_certificates.S
system_keyring.c
task_work.c
taskstats.c
test_kprobes.c
torture.c
tracepoint.c
tsacct.c
uid16.c
up.c
user_namespace.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace	2014-12-17 12:31:40 -08:00
user-return-notifier.c
user.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace	2014-12-17 12:31:40 -08:00
utsname_sysctl.c
utsname.c
watchdog.c
workqueue_internal.h
workqueue.c	workqueue: fix subtle pool management issue which can stall whole worker_pool	2015-01-16 14:21:16 -05:00