kernel/linux.git/include/linux/rcutiny.h, branch v6.12.80

Merge tag 'slab-for-6.12' of git://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab

2024-09-18T06:53:53+00:00

Pull slab updates from Vlastimil Babka: "This time it's mostly refactoring and improving APIs for slab users in the kernel, along with some debugging improvements. - kmem_cache_create() refactoring (Christian Brauner) Over the years have been growing new parameters to kmem_cache_create() where most of them are needed only for a small number of caches - most recently the rcu_freeptr_offset parameter. To avoid adding new parameters to kmem_cache_create() and adjusting all its callers, or creating new wrappers such as kmem_cache_create_rcu(), we can now pass extra parameters using the new struct kmem_cache_args. Not explicitly initialized fields default to values interpreted as unused. kmem_cache_create() is for now a wrapper that works both with the new form: kmem_cache_create(name, object_size, args, flags) and the legacy form: kmem_cache_create(name, object_size, align, flags, ctor) - kmem_cache_destroy() waits for kfree_rcu()'s in flight (Vlastimil Babka, Uladislau Rezki) Since SLOB removal, kfree() is allowed for freeing objects allocated by kmem_cache_create(). By extension kfree_rcu() as allowed as well, which can allow converting simple call_rcu() callbacks that only do kmem_cache_free(), as there was never a kmem_cache_free_rcu() variant. However, for caches that can be destroyed e.g. on module removal, the cache owners knew to issue rcu_barrier() first to wait for the pending call_rcu()'s, and this is not sufficient for pending kfree_rcu()'s due to its internal batching optimizations. Ulad has provided a new kvfree_rcu_barrier() and to make the usage less error-prone, kmem_cache_destroy() calls it. Additionally, destroying SLAB_TYPESAFE_BY_RCU caches now again issues rcu_barrier() synchronously instead of using an async work, because the past motivation for async work no longer applies. Users of custom call_rcu() callbacks should however keep calling rcu_barrier() before cache destruction. - Debugging use-after-free in SLAB_TYPESAFE_BY_RCU caches (Jann Horn) Currently, KASAN cannot catch UAFs in such caches as it is legal to access them within a grace period, and we only track the grace period when trying to free the underlying slab page. The new CONFIG_SLUB_RCU_DEBUG option changes the freeing of individual object to be RCU-delayed, after which KASAN can poison them. - Delayed memcg charging (Shakeel Butt) In some cases, the memcg is uknown at allocation time, such as receiving network packets in softirq context. With kmem_cache_charge() these may be now charged later when the user and its memcg is known. - Misc fixes and improvements (Pedro Falcato, Axel Rasmussen, Christoph Lameter, Yan Zhen, Peng Fan, Xavier)" * tag 'slab-for-6.12' of git://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab: (34 commits) mm, slab: restore kerneldoc for kmem_cache_create() io_uring: port to struct kmem_cache_args slab: make __kmem_cache_create() static inline slab: make kmem_cache_create_usercopy() static inline slab: remove kmem_cache_create_rcu() file: port to struct kmem_cache_args slab: create kmem_cache_create() compatibility layer slab: port KMEM_CACHE_USERCOPY() to struct kmem_cache_args slab: port KMEM_CACHE() to struct kmem_cache_args slab: remove rcu_freeptr_offset from struct kmem_cache slab: pass struct kmem_cache_args to do_kmem_cache_create() slab: pull kmem_cache_open() into do_kmem_cache_create() slab: pass struct kmem_cache_args to create_cache() slab: port kmem_cache_create_usercopy() to struct kmem_cache_args slab: port kmem_cache_create_rcu() to struct kmem_cache_args slab: port kmem_cache_create() to struct kmem_cache_args slab: add struct kmem_cache_args slab: s/__kmem_cache_create/do_kmem_cache_create/g memcg: add charging of already allocated slab objects mm/slab: Optimize the code logic in find_mergeable() ...

rcu/kvfree: Add kvfree_rcu_barrier() API

2024-08-27T12:12:51+00:00

Add a kvfree_rcu_barrier() function. It waits until all in-flight pointers are freed over RCU machinery. It does not wait any GP completion and it is within its right to return immediately if there are no outstanding pointers. This function is useful when there is a need to guarantee that a memory is fully freed before destroying memory caches. For example, during unloading a kernel module. Signed-off-by: Uladzislau Rezki (Sony) Signed-off-by: Vlastimil Babka

rcu: Rename rcu_momentary_dyntick_idle() into rcu_momentary_eqs()

2024-08-15T16:00:42+00:00

The context_tracking.state RCU_DYNTICKS subvariable has been renamed to RCU_WATCHING, replace "dyntick_idle" into "eqs" to drop the dyntick reference. Signed-off-by: Valentin Schneider Reviewed-by: Frederic Weisbecker Signed-off-by: Neeraj Upadhyay

rcu: Standardize explicit CPU-hotplug calls

2023-10-04T20:29:45+00:00

rcu_report_dead() and rcutree_migrate_callbacks() have their headers in rcupdate.h while those are pure rcutree calls, like the other CPU-hotplug functions. Also rcu_cpu_starting() and rcu_report_dead() have different naming conventions while they mirror each other's effects. Fix the headers and propose a naming that relates both functions and aligns with the prefix of other rcutree CPU-hotplug functions. Reviewed-by: Paul E. McKenney Signed-off-by: Frederic Weisbecker

rcu: Export rcu_request_urgent_qs_task()

2023-07-12T21:45:23+00:00

If a CPU is executing a long series of non-sleeping system calls, RCU grace periods can be delayed for on the order of a couple hundred milliseconds. This is normally not a problem, but if each system call does a call_rcu(), those callbacks can stack up. RCU will eventually notice this callback storm, but use of rcu_request_urgent_qs_task() allows the code invoking call_rcu() to give RCU a heads up. This function is not for general use, not yet, anyway. Reported-by: Alexei Starovoitov Signed-off-by: Paul E. McKenney Signed-off-by: Alexei Starovoitov Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20230706033447.54696-11-alexei.starovoitov@gmail.com

rcu: Refactor kvfree_call_rcu() and high-level helpers

2023-01-04T01:48:40+00:00

Currently a kvfree_call_rcu() takes an offset within a structure as a second parameter, so a helper such as a kvfree_rcu_arg_2() has to convert rcu_head and a freed ptr to an offset in order to pass it. That leads to an extra conversion on macro entry. Instead of converting, refactor the code in way that a pointer that has to be freed is passed directly to the kvfree_call_rcu(). This patch does not make any functional change and is transparent to all kvfree_rcu() users. Signed-off-by: Uladzislau Rezki (Sony) Signed-off-by: Paul E. McKenney

Merge tag 'printk-for-6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux

2022-12-12T17:01:36+00:00

Pull printk updates from Petr Mladek: - Add NMI-safe SRCU reader API. It uses atomic_inc() instead of this_cpu_inc() on strong load-store architectures. - Introduce new console_list_lock to synchronize a manipulation of the list of registered consoles and their flags. This is a first step in removing the big-kernel-lock-like behavior of console_lock(). This semaphore still serializes console->write() calbacks against: - each other. It primary prevents potential races between early and proper console drivers using the same device. - suspend()/resume() callbacks and init() operations in some drivers. - various other operations in the tty/vt and framebufer susbsystems. It is likely that console_lock() serializes even operations that are not directly conflicting with the console->write() callbacks here. This is the most complicated big-kernel-lock aspect of the console_lock() that will be hard to untangle. - Introduce new console_srcu lock that is used to safely iterate and access the registered console drivers under SRCU read lock. This is a prerequisite for introducing atomic console drivers and console kthreads. It will reduce the complexity of serialization against normal consoles and console_lock(). Also it should remove the risk of deadlock during critical situations, like Oops or panic, when only atomic consoles are registered. - Check whether the console is registered instead of enabled on many locations. It was a historical leftover. - Cleanly force a preferred console in xenfb code instead of a dirty hack. - A lot of code and comment clean ups and improvements. * tag 'printk-for-6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux: (47 commits) printk: htmldocs: add missing description tty: serial: sh-sci: use setup() callback for early console printk: relieve console_lock of list synchronization duties tty: serial: kgdboc: use console_list_lock to trap exit tty: serial: kgdboc: synchronize tty_find_polling_driver() and register_console() tty: serial: kgdboc: use console_list_lock for list traversal tty: serial: kgdboc: use srcu console list iterator proc: consoles: use console_list_lock for list iteration tty: tty_io: use console_list_lock for list synchronization printk, xen: fbfront: create/use safe function for forcing preferred netconsole: avoid CON_ENABLED misuse to track registration usb: early: xhci-dbc: use console_is_registered() tty: serial: xilinx_uartps: use console_is_registered() tty: serial: samsung_tty: use console_is_registered() tty: serial: pic32_uart: use console_is_registered() tty: serial: earlycon: use console_is_registered() tty: hvc: use console_is_registered() efi: earlycon: use console_is_registered() tty: nfcon: use console_is_registered() serial_core: replace uart_console_enabled() with uart_console_registered() ...

rcu: Make SRCU mandatory

2022-11-29T23:00:06+00:00

Kernels configured with CONFIG_PRINTK=n and CONFIG_SRCU=n get build failures. This causes trouble for deep embedded systems. But given that there are more than 25 instances of "select SRCU" in the kernel, it is hard to believe that there are many kernels running in production without SRCU. This commit therefore makes SRCU mandatory. The SRCU Kconfig option remains for backwards compatibility, and will be removed when it is no longer used. [ paulmck: Update per kernel test robot feedback. ] Reported-by: John Ogness Reported-by: Petr Mladek Signed-off-by: Paul E. McKenney Cc: Acked-by: Randy Dunlap # build-tested Reviewed-by: John Ogness

rcu: Remove rcu_is_idle_cpu()

2022-10-21T17:11:00+00:00

The commit 3fcd6a230fa7 ("x86/cpu: Avoid cpuinfo-induced IPIing of idle CPUs") introduced rcu_is_idle_cpu() in order to identify the current CPU idle state. But commit f3eca381bd49 ("x86/aperfmperf: Replace arch_freq_get_on_cpu()") switched to using MAX_SAMPLE_AGE, so rcu_is_idle_cpu() is no longer used. This commit therefore removes it. Fixes: f3eca381bd49 ("x86/aperfmperf: Replace arch_freq_get_on_cpu()") Signed-off-by: Yipeng Zou Reviewed-by: Frederic Weisbecker Signed-off-by: Paul E. McKenney

rcu: Remove unused 'cpu' in rcu_virt_note_context_switch()

2022-10-18T21:59:57+00:00

This commit removes the unused function argument 'cpu'. This does not change functionality, but might save a cycle or two. Signed-off-by: Zeng Heng Acked-by: Mukesh Ojha Signed-off-by: Paul E. McKenney