linux/kernel/rcu
Paul E. McKenney da123016ca rcu-tasks: Fix computation of CPU-to-list shift counts
The ->percpu_enqueue_shift field is used to map from the running CPU
number to the index of the corresponding callback list.  This mapping
can change at runtime in response to varying callback load, resulting
in varying levels of contention on the callback-list locks.

Unfortunately, the initial value of this field is correct only if the
system happens to have a power-of-two number of CPUs, otherwise the
callbacks from the high-numbered CPUs can be placed into the callback list
indexed by 1 (rather than 0), and those index-1 callbacks will be ignored.
This can result in soft lockups and hangs.

This commit therefore corrects this mapping, adding one to this shift
count as needed for systems having odd numbers of CPUs.

Fixes: 7a30871b6a ("rcu-tasks: Introduce ->percpu_enqueue_shift for dynamic queue selection")
Reported-by: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Reported-by: Martin Lau <kafai@fb.com>
Cc: Neeraj Upadhyay <neeraj.iitr10@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2022-01-26 13:04:05 -08:00
..
Kconfig Merge branches 'doc.2021.11.30c', 'exp.2021.12.07a', 'fastnohz.2021.11.30c', 'fixes.2021.11.30c', 'nocb.2021.12.09a', 'nolibc.2021.11.30c', 'tasks.2021.12.09a', 'torture.2021.12.07a' and 'torturescript.2021.11.30c' into HEAD 2021-12-09 11:38:09 -08:00
Kconfig.debug rcu: Restrict RCU_STRICT_GRACE_PERIOD to at most four CPUs 2021-05-10 16:22:54 -07:00
Makefile rcuperf: Change rcuperf to rcuscale 2020-08-24 18:39:24 -07:00
rcu_segcblist.c rcu/nocb: Invoke rcu_core() at the start of deoffloading 2021-12-07 16:24:44 -08:00
rcu_segcblist.h rcu/nocb: Prepare state machine for a new step 2021-12-07 16:24:44 -08:00
rcu.h Merge branches 'bitmaprange.2021.05.10c', 'doc.2021.05.10c', 'fixes.2021.05.13a', 'kvfree_rcu.2021.05.10c', 'mmdumpobj.2021.05.10c', 'nocb.2021.05.12a', 'srcu.2021.05.12a', 'tasks.2021.05.18a' and 'torture.2021.05.10c' into HEAD 2021-05-18 10:56:19 -07:00
rcuscale.c rcuscale: Always log error message 2021-12-07 16:36:17 -08:00
rcutorture.c Merge branch 'akpm' (patches from Andrew) 2022-01-15 20:37:06 +02:00
refscale.c refscale: Add missing '\n' to flush message 2021-12-07 16:36:12 -08:00
srcutiny.c srcu: Prevent redundant __srcu_read_unlock() wakeup 2021-11-30 17:28:16 -08:00
srcutree.c Merge branches 'bitmaprange.2021.05.10c', 'doc.2021.05.10c', 'fixes.2021.05.13a', 'kvfree_rcu.2021.05.10c', 'mmdumpobj.2021.05.10c', 'nocb.2021.05.12a', 'srcu.2021.05.12a', 'tasks.2021.05.18a' and 'torture.2021.05.10c' into HEAD 2021-05-18 10:56:19 -07:00
sync.c rcu: Fix various typos in comments 2021-05-12 12:11:05 -07:00
tasks.h rcu-tasks: Fix computation of CPU-to-list shift counts 2022-01-26 13:04:05 -08:00
tiny.c srcu: Initialize SRCU after timers 2021-05-10 16:03:35 -07:00
tree_exp.h rcu/exp: Mark current CPU as exp-QS in IPI loop second pass 2021-12-07 16:22:22 -08:00
tree_nocb.h rcu/nocb: Merge rcu_spawn_cpu_nocb_kthread() and rcu_spawn_one_nocb_kthread() 2021-12-09 11:35:16 -08:00
tree_plugin.h Merge branches 'doc.2021.11.30c', 'exp.2021.12.07a', 'fastnohz.2021.11.30c', 'fixes.2021.11.30c', 'nocb.2021.12.09a', 'nolibc.2021.11.30c', 'tasks.2021.12.09a', 'torture.2021.12.07a' and 'torturescript.2021.11.30c' into HEAD 2021-12-09 11:38:09 -08:00
tree_stall.h rcu: Remove the RCU_FAST_NO_HZ Kconfig option 2021-11-30 17:24:47 -08:00
tree.c Merge branches 'doc.2021.11.30c', 'exp.2021.12.07a', 'fastnohz.2021.11.30c', 'fixes.2021.11.30c', 'nocb.2021.12.09a', 'nolibc.2021.11.30c', 'tasks.2021.12.09a', 'torture.2021.12.07a' and 'torturescript.2021.11.30c' into HEAD 2021-12-09 11:38:09 -08:00
tree.h Merge branches 'doc.2021.11.30c', 'exp.2021.12.07a', 'fastnohz.2021.11.30c', 'fixes.2021.11.30c', 'nocb.2021.12.09a', 'nolibc.2021.11.30c', 'tasks.2021.12.09a', 'torture.2021.12.07a' and 'torturescript.2021.11.30c' into HEAD 2021-12-09 11:38:09 -08:00
update.c RCU pull request for v5.16 2021-11-01 20:25:38 -07:00