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authorLinus Torvalds <torvalds@linux-foundation.org>2022-12-12 18:47:15 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2022-12-12 18:47:15 +0300
commit1fab45ab6e823f9d7e5bc9520b2aa6564d6d58a7 (patch)
tree0fed32c7ec3b36f8050c49281c3161ec3834df9a /include/linux/slab.h
parent830b3c68c1fb1e9176028d02ef86f3cf76aa2476 (diff)
parent87492c06e68d802852c7ba76b4d3fde50807d72a (diff)
downloadlinux-1fab45ab6e823f9d7e5bc9520b2aa6564d6d58a7.tar.xz
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 ...
Diffstat (limited to 'include/linux/slab.h')
-rw-r--r--include/linux/slab.h11
1 files changed, 11 insertions, 0 deletions
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 45efc6c553b8..e7534a7b2daf 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -76,6 +76,17 @@
* rcu_read_lock before reading the address, then rcu_read_unlock after
* taking the spinlock within the structure expected at that address.
*
+ * Note that it is not possible to acquire a lock within a structure
+ * allocated with SLAB_TYPESAFE_BY_RCU without first acquiring a reference
+ * as described above. The reason is that SLAB_TYPESAFE_BY_RCU pages
+ * are not zeroed before being given to the slab, which means that any
+ * locks must be initialized after each and every kmem_struct_alloc().
+ * Alternatively, make the ctor passed to kmem_cache_create() initialize
+ * the locks at page-allocation time, as is done in __i915_request_ctor(),
+ * sighand_ctor(), and anon_vma_ctor(). Such a ctor permits readers
+ * to safely acquire those ctor-initialized locks under rcu_read_lock()
+ * protection.
+ *
* Note that SLAB_TYPESAFE_BY_RCU was originally named SLAB_DESTROY_BY_RCU.
*/
/* Defer freeing slabs to RCU */