kernel/linux.git/include/linux/rcupdate.h, branch v6.1.168

rcu: handle unstable rdp in rcu_read_unlock_strict()

2025-06-04T12:40:16+00:00

[ Upstream commit fcf0e25ad4c8d14d2faab4d9a17040f31efce205 ] rcu_read_unlock_strict() can be called with preemption enabled which can make for an unstable rdp and a racy norm value. Fix this by dropping the preempt-count in __rcu_read_unlock() after the call to rcu_read_unlock_strict(), adjusting the preempt-count check appropriately. Suggested-by: Frederic Weisbecker Signed-off-by: Ankur Arora Reviewed-by: Frederic Weisbecker Signed-off-by: Paul E. McKenney Signed-off-by: Boqun Feng Signed-off-by: Sasha Levin

rcu/kvfree: Add kvfree_rcu_mightsleep() and kfree_rcu_mightsleep()

2025-05-18T06:21:21+00:00

[ Upstream commit 608723c41cd951fb32ade2f8371e61c270816175 ] The kvfree_rcu() and kfree_rcu() APIs are hazardous in that if you forget the second argument, it works, but might sleep. This sleeping can be a correctness bug from atomic contexts, and even in non-atomic contexts it might introduce unacceptable latencies. This commit therefore adds kvfree_rcu_mightsleep() and kfree_rcu_mightsleep(), which will replace the single-argument kvfree_rcu() and kfree_rcu(), respectively. This commit enables a series of commits that switch from single-argument kvfree_rcu() and kfree_rcu() to their _mightsleep() counterparts. Once all of these commits land, the single-argument versions will be removed. Signed-off-by: Uladzislau Rezki (Sony) Signed-off-by: Paul E. McKenney Stable-dep-of: 511e64e13d8c ("can: gw: fix RCU/BH usage in cgw_create_job()") Signed-off-by: Sasha Levin

rcu-tasks: Always inline rcu_irq_work_resched()

2025-04-10T12:33:38+00:00

[ Upstream commit 6309a5c43b0dc629851f25b2e5ef8beff61d08e5 ] Thanks to CONFIG_DEBUG_SECTION_MISMATCH, empty functions can be generated out of line. rcu_irq_work_resched() can be called from noinstr code, so make sure it's always inlined. Fixes: 564506495ca9 ("rcu/context-tracking: Move deferred nocb resched to context tracking") Reported-by: Randy Dunlap Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar Cc: Frederic Weisbecker Cc: Paul E. McKenney Cc: Linus Torvalds Link: https://lore.kernel.org/r/e84f15f013c07e4c410d972e75620c53b62c1b3e.1743481539.git.jpoimboe@kernel.org Closes: https://lore.kernel.org/d1eca076-fdde-484a-b33e-70e0d167c36d@infradead.org Signed-off-by: Sasha Levin

rcu-tasks: Repair RCU Tasks Trace quiescence check

2024-04-13T11:05:07+00:00

[ Upstream commit 2eb52fa8900e642b3b5054c4bf9776089d2a935f ] The context-switch-time check for RCU Tasks Trace quiescence expects current->trc_reader_special.b.need_qs to be zero, and if so, updates it to TRC_NEED_QS_CHECKED. This is backwards, because if this value is zero, there is no RCU Tasks Trace grace period in flight, an thus no need for a quiescent state. Instead, when a grace period starts, this field is set to TRC_NEED_QS. This commit therefore changes the check from zero to TRC_NEED_QS. Reported-by: Steven Rostedt Signed-off-by: Paul E. McKenney Tested-by: Steven Rostedt (Google) Signed-off-by: Boqun Feng Signed-off-by: Sasha Levin

rcu: add a helper to report consolidated flavor QS

2024-03-26T22:21:02+00:00

[ Upstream commit 1a77557d48cff187a169c2aec01c0dd78a5e7e50 ] When under heavy load, network processing can run CPU-bound for many tens of seconds. Even in preemptible kernels (non-RT kernel), this can block RCU Tasks grace periods, which can cause trace-event removal to take more than a minute, which is unacceptably long. This commit therefore creates a new helper function that passes through both RCU and RCU-Tasks quiescent states every 100 milliseconds. This hard-coded value suffices for current workloads. Suggested-by: Paul E. McKenney Reviewed-by: Jesper Dangaard Brouer Signed-off-by: Yan Zhai Reviewed-by: Paul E. McKenney Acked-by: Jesper Dangaard Brouer Link: https://lore.kernel.org/r/90431d46ee112d2b0af04dbfe936faaca11810a5.1710877680.git.yan@cloudflare.com Signed-off-by: Jakub Kicinski Stable-dep-of: d6dbbb11247c ("net: report RCU QS on threaded NAPI repolling") Signed-off-by: Sasha Levin

locking: Introduce __cleanup() based infrastructure

2024-02-23T08:12:51+00:00

commit 54da6a0924311c7cf5015533991e44fb8eb12773 upstream. Use __attribute__((__cleanup__(func))) to build: - simple auto-release pointers using __free() - 'classes' with constructor and destructor semantics for scope-based resource management. - lock guards based on the above classes. Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20230612093537.614161713%40infradead.org Signed-off-by: Greg Kroah-Hartman

rcu-tasks: Provide rcu_trace_implies_rcu_gp()

2024-01-25T23:27:26+00:00

[ Upstream commit e6c86c513f440bec5f1046539c7e3c6c653842da ] As an accident of implementation, an RCU Tasks Trace grace period also acts as an RCU grace period. However, this could change at any time. This commit therefore creates an rcu_trace_implies_rcu_gp() that currently returns true to codify this accident. Code relying on this accident must call this function to verify that this accident is still happening. Reported-by: Hou Tao Signed-off-by: Paul E. McKenney Cc: Alexei Starovoitov Cc: Martin KaFai Lau Link: https://lore.kernel.org/r/20221014113946.965131-2-houtao@huaweicloud.com Signed-off-by: Alexei Starovoitov Stable-dep-of: 876673364161 ("bpf: Defer the free of inner map when necessary") Signed-off-by: Sasha Levin

rcu: Make RCU_LOCKDEP_WARN() avoid early lockdep checks

2023-03-10T08:33:48+00:00

[ Upstream commit 0cae5ded535c3a80aed94f119bbd4ee3ae284a65 ] Currently, RCU_LOCKDEP_WARN() checks the condition before checking to see if lockdep is still enabled. This is necessary to avoid the false-positive splats fixed by commit 3066820034b5dd ("rcu: Reject RCU_LOCKDEP_WARN() false positives"). However, the current state can result in false-positive splats during early boot before lockdep is fully initialized. This commit therefore checks debug_lockdep_rcu_enabled() both before and after checking the condition, thus avoiding both sets of false-positive error reports. Reported-by: Steven Rostedt Reported-by: Masami Hiramatsu (Google) Reported-by: Mathieu Desnoyers Signed-off-by: Paul E. McKenney Reviewed-by: Mathieu Desnoyers Cc: Boqun Feng Cc: Matthew Wilcox Cc: Thomas Gleixner Signed-off-by: Sasha Levin

rcu-tasks: Fix synchronize_rcu_tasks() VS zap_pid_ns_processes()

2023-03-10T08:32:52+00:00

[ Upstream commit 28319d6dc5e2ffefa452c2377dd0f71621b5bff0 ] RCU Tasks and PID-namespace unshare can interact in do_exit() in a complicated circular dependency: 1) TASK A calls unshare(CLONE_NEWPID), this creates a new PID namespace that every subsequent child of TASK A will belong to. But TASK A doesn't itself belong to that new PID namespace. 2) TASK A forks() and creates TASK B. TASK A stays attached to its PID namespace (let's say PID_NS1) and TASK B is the first task belonging to the new PID namespace created by unshare() (let's call it PID_NS2). 3) Since TASK B is the first task attached to PID_NS2, it becomes the PID_NS2 child reaper. 4) TASK A forks() again and creates TASK C which get attached to PID_NS2. Note how TASK C has TASK A as a parent (belonging to PID_NS1) but has TASK B (belonging to PID_NS2) as a pid_namespace child_reaper. 5) TASK B exits and since it is the child reaper for PID_NS2, it has to kill all other tasks attached to PID_NS2, and wait for all of them to die before getting reaped itself (zap_pid_ns_process()). 6) TASK A calls synchronize_rcu_tasks() which leads to synchronize_srcu(&tasks_rcu_exit_srcu). 7) TASK B is waiting for TASK C to get reaped. But TASK B is under a tasks_rcu_exit_srcu SRCU critical section (exit_notify() is between exit_tasks_rcu_start() and exit_tasks_rcu_finish()), blocking TASK A. 8) TASK C exits and since TASK A is its parent, it waits for it to reap TASK C, but it can't because TASK A waits for TASK B that waits for TASK C. Pid_namespace semantics can hardly be changed at this point. But the coverage of tasks_rcu_exit_srcu can be reduced instead. The current task is assumed not to be concurrently reapable at this stage of exit_notify() and therefore tasks_rcu_exit_srcu can be temporarily relaxed without breaking its constraints, providing a way out of the deadlock scenario. [ paulmck: Fix build failure by adding additional declaration. ] Fixes: 3f95aa81d265 ("rcu: Make TASKS_RCU handle tasks that are almost done exiting") Reported-by: Pengfei Xu Suggested-by: Boqun Feng Suggested-by: Neeraj Upadhyay Suggested-by: Paul E. McKenney Cc: Oleg Nesterov Cc: Lai Jiangshan Cc: Eric W . Biederman Signed-off-by: Frederic Weisbecker Signed-off-by: Paul E. McKenney Signed-off-by: Sasha Levin

Merge branches 'doc.2022.08.31b', 'fixes.2022.08.31b', 'kvfree.2022.08.31b', 'nocb.2022.09.01a', 'poll.2022.08.31b', 'poll-srcu.2022.08.31b' and 'tasks.2022.08.31b' into HEAD

2022-09-01T17:55:57+00:00

doc.2022.08.31b: Documentation updates fixes.2022.08.31b: Miscellaneous fixes kvfree.2022.08.31b: kvfree_rcu() updates nocb.2022.09.01a: NOCB CPU updates poll.2022.08.31b: Full-oldstate RCU polling grace-period API poll-srcu.2022.08.31b: Polled SRCU grace-period updates tasks.2022.08.31b: Tasks RCU updates