1fab45ab6e
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: 0cd7e350abc4 ("rcu: Make SRCU mandatory") 51f5f78a4f80 ("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----- iQJHBAABCgAxFiEEbK7UrM+RBIrCoViJnr8S83LZ+4wFAmOKnS8THHBhdWxtY2tA a2VybmVsLm9yZwAKCRCevxLzctn7jCMiD/4weraRjmcLhZ3tz2vgTI8ZsXdIiCfU vCln0AOKroVo37S4BhViVfryV2D4VFfEb1UY6EgxNFu7Jd3z0seQShZh/5r8bFMU p0E6TC8PwyKUpQstTOwOynkw6BWGW1qeL620PpBNRAy4MkxL8AGv40tHRIHEeAzc cCTax2+xW9ae0ZtAZHDDCUAzpYpcjScIf4OZ3tkSaFCcpWZijg+dN60dnsZ9l7h9 DtqKH61rszXAtxkmN9Fs9OY5MPCXi9Es6LVYq6KN06jqxwJRqmYf+pai3apmNIOf P8isXOQG58tbhBLpNCG58UBSkjI2GG8Lcq6hYr6d/7Ukm7RF49q8eL7OQlVrJMuQ Zi2DVTEAu2U3pzdTC14gi3RvqP7dO+psBs+LpGXtj4RxYvAP99e9KSRcG14j/Wwa L52AetBzBXTCS5nhPOG8RP22d8HRZLxMe9x7T8iVCDuwH4M1zTF5cVzLeEdgPAD7 tdX4eV16PLt1AvhCEuHU/2v520gc2K9oGXLI1A6kzquXh7FflcPWl5WS+sYUbB/p gBsblz7C3I5GgSoW4aAMnkukZiYgSvVql8ZyRwQuRzvLpYcofMpoanZbcufDjuw9 N5QzAaMmzHnBu3hOJS2WaSZRZ73fed3NO8jo8q8EMfYeWK3NAHybBdaQqSTgsO8i s+aN+LZ4s5MnRw== =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 ...