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Paul E. McKenney 39bbfc62cc rcu: Expedite deboost in case of deferred quiescent state 
Historically, a task that has been subjected to RCU priority boosting is
deboosted at rcu_read_unlock() time.  However, with the advent of deferred
quiescent states, if the outermost rcu_read_unlock() was invoked with
either bottom halves, interrupts, or preemption disabled, the deboosting
will be delayed for some time.  During this time, a low-priority process
might be incorrectly running at a high real-time priority level.

Fortunately, rcu_read_unlock_special() already provides mechanisms for
forcing a minimal deferral of quiescent states, at least for kernels
built with CONFIG_IRQ_WORK=y.  These mechanisms are currently used
when expedited grace periods are pending that might be blocked by the
current task.  This commit therefore causes those mechanisms to also be
used in cases where the current task has been or might soon be subjected
to RCU priority boosting.  Note that this applies to all kernels built
with CONFIG_RCU_BOOST=y, regardless of whether or not they are also
built with CONFIG_PREEMPT_RT=y.

This approach assumes that kernels build for use with aggressive real-time
applications are built with CONFIG_IRQ_WORK=y.  It is likely to be far
simpler to enable CONFIG_IRQ_WORK=y than to implement a fast-deboosting
scheme that works correctly in its absence.

While in the area, alphabetize the rcu_preempt_deferred_qs_handler()
function's local variables.

Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Scott Wood <swood@redhat.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
 		2021-03-08 14:21:40 -08:00
..
bpf idmapped-mounts-v5.12 2021-02-23 13:39:45 -08:00
cgroup idmapped-mounts-v5.12 2021-02-23 13:39:45 -08:00
configs staging: ION: remove some references to CONFIG_ION 2021-01-06 17:39:38 +01:00
debug kgdb: fix to kill breakpoints on initmem after boot 2021-02-26 09:41:05 -08:00
dma Merge branch 'stable/for-linus-5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/swiotlb 2021-02-26 13:59:32 -08:00
entry entry: Explicitly flush pending rcuog wakeup before last rescheduling point 2021-02-17 14:12:43 +01:00
events kernel: delete repeated words in comments 2021-02-26 09:41:03 -08:00
gcov init/gcov: allow CONFIG_CONSTRUCTORS on UML to fix module gcov 2021-02-05 11:03:47 -08:00
irq Driver core / debugfs update for 5.12-rc1 2021-02-24 10:13:55 -08:00
kcsan kcsan: Rewrite kcsan_prandom_u32_max() without prandom_u32_state() 2021-01-04 14:39:07 -08:00
livepatch kallsyms: refactor {,module_}kallsyms_on_each_symbol 2021-02-08 12:22:08 +01:00
locking kernel: delete repeated words in comments 2021-02-26 09:41:03 -08:00
power Merge branches 'powercap' and 'pm-misc' 2021-02-15 18:50:01 +01:00
printk Merge branch 'printk-rework' into for-linus 2021-02-22 13:43:55 +01:00
rcu rcu: Expedite deboost in case of deferred quiescent state 2021-03-08 14:21:40 -08:00
sched kernel: delete repeated words in comments 2021-02-26 09:41:03 -08:00
time These are the latest RCU updates for v5.12: 2021-02-21 12:04:41 -08:00
trace tracing: Skip selftests if tracing is disabled 2021-03-04 09:51:25 -05:00
.gitignore
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Kconfig.freezer
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Kconfig.hz
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Kconfig.locks
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Kconfig.preempt preempt: Introduce CONFIG_PREEMPT_DYNAMIC 2021-02-17 14:12:24 +01:00
Makefile kcmp: Support selection of SYS_kcmp without CHECKPOINT_RESTORE 2021-02-16 09:59:41 +01:00
acct.c kernel/acct.c: use #elif instead of #end and #elif 2020-12-15 22:46:15 -08:00
async.c treewide: Remove uninitialized_var() usage 2020-07-16 12:35:15 -07:00
audit.c audit: Remove leftover reference to the audit_tasklet 2021-01-15 11:58:10 -05:00
audit.h audit: change unnecessary globals into statics 2020-08-17 20:26:58 -04:00
audit_fsnotify.c audit_alloc_mark(): don't open-code ERR_CAST() 2021-02-23 10:25:27 -05:00
audit_tree.c fsnotify: generalize handle_inode_event() 2020-12-03 14:58:35 +01:00
audit_watch.c fsnotify: generalize handle_inode_event() 2020-12-03 14:58:35 +01:00
auditfilter.c treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
auditsc.c idmapped-mounts-v5.12 2021-02-23 13:39:45 -08:00
backtracetest.c treewide: Replace DECLARE_TASKLET() with DECLARE_TASKLET_OLD() 2020-07-30 11:15:58 -07:00
bounds.c
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capability.c capability: handle idmapped mounts 2021-01-24 14:27:16 +01:00
compat.c treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
configs.c
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context_tracking.c
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cpu.c cpu/hotplug: Add lockdep_is_cpus_held() 2021-01-06 16:24:59 -08:00
cpu_pm.c notifier: Fix broken error handling pattern 2020-09-01 09:58:03 +02:00
crash_core.c kdump: append uts_namespace.name offset to VMCOREINFO 2020-12-15 22:46:18 -08:00
crash_dump.c
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cred.c
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delayacct.c
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dma.c
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exec_domain.c
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exit.c kernel/io_uring: cancel io_uring before task works 2020-12-30 19:36:54 -07:00
extable.c
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fail_function.c fault-injection: handle EI_ETYPE_TRUE 2020-12-15 22:46:19 -08:00
fork.c kernel: provide create_io_thread() helper 2021-03-04 15:45:03 -07:00
freezer.c
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futex.c Merge branch 'linus' into locking/core, to pick up upstream fixes 2021-02-12 12:54:58 +01:00
gen_kheaders.sh
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groups.c groups: simplify struct group_info allocation 2021-02-26 09:41:03 -08:00
hung_task.c kernel/hung_task.c: make type annotations consistent 2020-11-02 12:14:19 -08:00
iomem.c
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irq_work.c irq_work: Optimize irq_work_single() 2020-11-24 16:47:49 +01:00
jump_label.c jump_label: Fix usage in module __init 2020-12-18 16:53:12 +01:00
kallsyms.c kallsyms: only build {,module_}kallsyms_on_each_symbol when required 2021-02-08 12:24:04 +01:00
kcmp.c Merge branch 'exec-update-lock-for-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2020-12-15 19:36:48 -08:00
kcov.c kernel: make kcov_common_handle consider the current context 2020-11-02 18:00:20 -08:00
kexec.c LSM: Introduce kernel_post_load_data() hook 2020-10-05 13:37:03 +02:00
kexec_core.c Merge branch 'work.elf-compat' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2021-02-21 09:29:23 -08:00
kexec_elf.c
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kexec_file.c ima: Free IMA measurement buffer after kexec syscall 2021-02-10 15:49:38 -05:00
kexec_internal.h kexec: move machine_kexec_post_load() to public interface 2021-02-22 12:33:26 +00:00
kheaders.c
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kmod.c kmod: remove redundant "be an" in the comment 2020-08-12 10:58:01 -07:00
kprobes.c kprobes: Fix to delay the kprobes jump optimization 2021-02-19 14:57:12 -05:00
ksysfs.c
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kthread.c - Correct the marking of kthreads which are supposed to run on a specific, 2021-01-24 10:09:20 -08:00
latencytop.c
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module-internal.h
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module.c module: potential uninitialized return in module_kallsyms_on_each_symbol() 2021-02-10 16:57:04 +01:00
module_signature.c module: harden ELF info handling 2021-01-19 10:24:45 +01:00
module_signing.c module: harden ELF info handling 2021-01-19 10:24:45 +01:00
notifier.c notifier: Fix broken error handling pattern 2020-09-01 09:58:03 +02:00
nsproxy.c fixes-v5.11 2020-12-14 16:40:27 -08:00
padata.c padata: fix possible padata_works_lock deadlock 2020-09-04 17:51:55 +10:00
panic.c panic: don't dump stack twice on warn 2020-11-14 11:26:04 -08:00
params.c Modules updates for v5.11 2020-12-17 13:01:31 -08:00
pid.c Merge branch 'exec-update-lock-for-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2020-12-15 19:36:48 -08:00
pid_namespace.c fixes-v5.11 2020-12-14 16:40:27 -08:00
profile.c
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ptrace.c kernel: treat PF_IO_WORKER like PF_KTHREAD for ptrace/signals 2021-02-21 17:25:22 -07:00
range.c kernel.h: split out min()/max() et al. helpers 2020-10-16 11:11:19 -07:00
reboot.c reboot: hide from sysfs not applicable settings 2020-12-15 22:46:19 -08:00
regset.c regset: kill ->get() 2020-07-27 14:31:12 -04:00
relay.c relay: allow the use of const callback structs 2020-12-15 22:46:18 -08:00
resource.c resource: Move devmem revoke code to resource framework 2021-01-12 14:26:31 +01:00
resource_kunit.c resource: provide meaningful MODULE_LICENSE() in test suite 2020-11-25 18:52:35 +01:00
rseq.c
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scftorture.c scftorture: Add debug output for wrong-CPU warning 2021-01-04 13:53:41 -08:00
scs.c scs: switch to vmapped shadow stacks 2020-12-01 10:30:28 +00:00
seccomp.c seccomp: Improve performace by optimizing rmb() 2021-02-10 12:40:11 -08:00
signal.c kernel: treat PF_IO_WORKER like PF_KTHREAD for ptrace/signals 2021-02-21 17:25:22 -07:00
smp.c smp: Process pending softirqs in flush_smp_call_function_from_idle() 2021-02-17 14:12:42 +01:00
smpboot.c kthread: Extract KTHREAD_IS_PER_CPU 2021-01-22 15:09:42 +01:00
smpboot.h
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softirq.c softirq: Move do_softirq_own_stack() to generic asm header 2021-02-10 23:34:16 +01:00
stackleak.c stackleak: let stack_erasing_sysctl take a kernel pointer buffer 2020-09-19 13:13:39 -07:00
stacktrace.c stacktrace: Remove reliable argument from arch_stack_walk() callback 2020-09-18 14:24:16 +01:00
static_call.c static_call: Allow module use without exposing static_call_key 2021-02-17 14:12:42 +01:00
stop_machine.c Merge branch 'linus' into sched/core, to resolve semantic conflict 2020-11-27 11:10:50 +01:00
sys.c Kbuild updates for v5.12 2021-02-25 10:17:31 -08:00
sys_ni.c epoll: wire up syscall epoll_pwait2 2020-12-19 11:18:38 -08:00
sysctl-test.c
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sysctl.c sysctl.c: fix underflow value setting risk in vm_table 2021-02-26 09:41:03 -08:00
task_work.c task_work: remove legacy TWA_SIGNAL path 2020-12-12 09:17:38 -07:00
taskstats.c treewide: rename nla_strlcpy to nla_strscpy. 2020-11-16 08:08:54 -08:00
test_kprobes.c
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torture.c torture: Maintain torture-specific set of CPUs-online books 2021-01-06 17:17:22 -08:00
tracepoint.c tracepoints: Code clean up 2021-02-09 12:27:29 -05:00
tsacct.c
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ucount.c
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uid16.c
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uid16.h
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umh.c usermodehelper: reset umask to default before executing user process 2020-10-06 10:31:52 -07:00
up.c
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user-return-notifier.c
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user.c user: Use generic ns_common::count 2020-08-19 14:14:12 +02:00
user_namespace.c fixes-v5.11 2020-12-14 16:40:27 -08:00
usermode_driver.c
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utsname.c uts: Use generic ns_common::count 2020-08-19 14:13:20 +02:00
utsname_sysctl.c
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watch_queue.c watch_queue: rectify kernel-doc for init_watch() 2021-01-26 11:16:34 +00:00
watchdog.c kernel/watchdog: fix watchdog_allowed_mask not used warning 2020-11-14 11:26:03 -08:00
watchdog_hld.c
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workqueue.c Merge branch 'for-5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq 2021-02-22 17:06:54 -08:00
workqueue_internal.h
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