This pull request contains the following branches:
doc.2022.10.20a: Documentation updates. This is the second
in a series from an ongoing review of the RCU documentation.
fixes.2022.10.21a: Miscellaneous fixes.
lazy.2022.11.30a: Introduces a default-off Kconfig option that depends
on RCU_NOCB_CPU that, on CPUs mentioned in the nohz_full or
rcu_nocbs boot-argument CPU lists, causes call_rcu() to introduce
delays. These delays result in significant power savings on
nearly idle Android and ChromeOS systems. These savings range
from a few percent to more than ten percent.
This series also includes several commits that change call_rcu()
to a new call_rcu_hurry() function that avoids these delays in
a few cases, for example, where timely wakeups are required.
Several of these are outside of RCU and thus have acks and
reviews from the relevant maintainers.
srcunmisafe.2022.11.09a: Creates an srcu_read_lock_nmisafe() and an
srcu_read_unlock_nmisafe() for architectures that support NMIs,
but which do not provide NMI-safe this_cpu_inc(). These NMI-safe
SRCU functions are required by the upcoming lockless printk()
work by John Ogness et al.
That printk() series depends on these commits, so if you pull
the printk() series before this one, you will have already
pulled in this branch, plus two more SRCU commits:
0cd7e350ab ("rcu: Make SRCU mandatory")
51f5f78a4f ("srcu: Make Tiny synchronize_srcu() check for readers")
These two commits appear to work well, but do not have
sufficient testing exposure over a long enough time for me to
feel comfortable pushing them unless something in mainline is
definitely going to use them immediately, and currently only
the new printk() work uses them.
torture.2022.10.18c: Changes providing minor but important increases
in test coverage for the new RCU polled-grace-period APIs.
torturescript.2022.10.20a: Changes that avoid redundant kernel builds,
thus providing about a 30% speedup for the torture.sh acceptance
test.
-----BEGIN PGP SIGNATURE-----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=eMOr
-----END PGP SIGNATURE-----
Merge tag 'rcu.2022.12.02a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu
Pull RCU updates from Paul McKenney:
- Documentation updates. This is the second in a series from an ongoing
review of the RCU documentation.
- Miscellaneous fixes.
- Introduce a default-off Kconfig option that depends on RCU_NOCB_CPU
that, on CPUs mentioned in the nohz_full or rcu_nocbs boot-argument
CPU lists, causes call_rcu() to introduce delays.
These delays result in significant power savings on nearly idle
Android and ChromeOS systems. These savings range from a few percent
to more than ten percent.
This series also includes several commits that change call_rcu() to a
new call_rcu_hurry() function that avoids these delays in a few
cases, for example, where timely wakeups are required. Several of
these are outside of RCU and thus have acks and reviews from the
relevant maintainers.
- Create an srcu_read_lock_nmisafe() and an srcu_read_unlock_nmisafe()
for architectures that support NMIs, but which do not provide
NMI-safe this_cpu_inc(). These NMI-safe SRCU functions are required
by the upcoming lockless printk() work by John Ogness et al.
- Changes providing minor but important increases in torture test
coverage for the new RCU polled-grace-period APIs.
- Changes to torturescript that avoid redundant kernel builds, thus
providing about a 30% speedup for the torture.sh acceptance test.
* tag 'rcu.2022.12.02a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu: (49 commits)
net: devinet: Reduce refcount before grace period
net: Use call_rcu_hurry() for dst_release()
workqueue: Make queue_rcu_work() use call_rcu_hurry()
percpu-refcount: Use call_rcu_hurry() for atomic switch
scsi/scsi_error: Use call_rcu_hurry() instead of call_rcu()
rcu/rcutorture: Use call_rcu_hurry() where needed
rcu/rcuscale: Use call_rcu_hurry() for async reader test
rcu/sync: Use call_rcu_hurry() instead of call_rcu
rcuscale: Add laziness and kfree tests
rcu: Shrinker for lazy rcu
rcu: Refactor code a bit in rcu_nocb_do_flush_bypass()
rcu: Make call_rcu() lazy to save power
rcu: Implement lockdep_rcu_enabled for !CONFIG_DEBUG_LOCK_ALLOC
srcu: Debug NMI safety even on archs that don't require it
srcu: Explain the reason behind the read side critical section on GP start
srcu: Warn when NMI-unsafe API is used in NMI
arch/s390: Add ARCH_HAS_NMI_SAFE_THIS_CPU_OPS Kconfig option
arch/loongarch: Add ARCH_HAS_NMI_SAFE_THIS_CPU_OPS Kconfig option
rcu: Fix __this_cpu_read() lockdep warning in rcu_force_quiescent_state()
rcu-tasks: Make grace-period-age message human-readable
...
1fab45ab6e