kernel_optimize_test/kernel/rcu
Yanfei Xu 527b56d785 rcu: Fix to include first blocked task in stall warning
[ Upstream commit e6a901a44f76878ed1653626c9ff4cfc5a3f58f8 ]

The for loop in rcu_print_task_stall() always omits ts[0], which points
to the first task blocking the stalled grace period.  This in turn fails
to count this first task, which means that ndetected will be equal to
zero when all CPUs have passed through their quiescent states and only
one task is blocking the stalled grace period.  This zero value for
ndetected will in turn result in an incorrect "All QSes seen" message:

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu:    Tasks blocked on level-1 rcu_node (CPUs 12-23):
        (detected by 15, t=6504 jiffies, g=164777, q=9011209)
rcu: All QSes seen, last rcu_preempt kthread activity 1 (4295252379-4295252378), jiffies_till_next_fqs=1, root ->qsmask 0x2
BUG: sleeping function called from invalid context at include/linux/uaccess.h:156
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 70613, name: msgstress04
INFO: lockdep is turned off.
Preemption disabled at:
[<ffff8000104031a4>] create_object.isra.0+0x204/0x4b0
CPU: 15 PID: 70613 Comm: msgstress04 Kdump: loaded Not tainted
5.12.2-yoctodev-standard #1
Hardware name: Marvell OcteonTX CN96XX board (DT)
Call trace:
 dump_backtrace+0x0/0x2cc
 show_stack+0x24/0x30
 dump_stack+0x110/0x188
 ___might_sleep+0x214/0x2d0
 __might_sleep+0x7c/0xe0

This commit therefore fixes the loop to include ts[0].

Fixes: c583bcb8f5 ("rcu: Don't invoke try_invoke_on_locked_down_task() with irqs disabled")
Tested-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Yanfei Xu <yanfei.xu@windriver.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-09-15 09:50:28 +02:00
..
Kconfig rcu: Reduce leaf fanout for strict RCU grace periods 2020-08-24 18:40:23 -07:00
Kconfig.debug Merge branch 'strictgp.2020.08.24a' into HEAD 2020-09-03 09:47:42 -07:00
Makefile rcuperf: Change rcuperf to rcuscale 2020-08-24 18:39:24 -07:00
rcu_segcblist.c rcu/segcblist: Prevent useless GP start if no CBs to accelerate 2020-09-03 09:39:59 -07:00
rcu_segcblist.h
rcu.h srcu: Fix broken node geometry after early ssp init 2021-07-20 16:05:38 +02:00
rcuscale.c rcuperf: Change rcuperf to rcuscale 2020-08-24 18:39:24 -07:00
rcutorture.c rcutorture: Allow pointer leaks to test diagnostic code 2020-08-24 18:45:36 -07:00
refscale.c refperf: Avoid null pointer dereference when buf fails to allocate 2020-08-24 18:45:35 -07:00
srcutiny.c srcu: Provide polling interfaces for Tiny SRCU grace periods 2021-09-03 10:09:30 +02:00
srcutree.c srcu: Provide polling interfaces for Tree SRCU grace periods 2021-09-03 10:09:29 +02:00
sync.c
tasks.h rcu-tasks: Don't delete holdouts within trc_wait_for_one_reader() 2021-07-31 08:16:11 +02:00
tiny.c rcu: Rename *_kfree_callback/*_kfree_rcu_offset/kfree_call_* 2020-06-29 11:59:25 -07:00
tree_exp.h rcu: Initialize at declaration time in rcu_exp_handler() 2020-08-24 18:36:03 -07:00
tree_plugin.h rcu/nocb: Perform deferred wake up before last idle's need_resched() check 2021-03-04 11:38:35 +01:00
tree_stall.h rcu: Fix to include first blocked task in stall warning 2021-09-15 09:50:28 +02:00
tree.c srcu: Fix broken node geometry after early ssp init 2021-07-20 16:05:38 +02:00
tree.h Merge branch 'strictgp.2020.08.24a' into HEAD 2020-09-03 09:47:42 -07:00
update.c rcu: Reject RCU_LOCKDEP_WARN() false positives 2021-07-20 16:05:38 +02:00