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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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6be7436d22
This commit adds rcu_gp_might_be_stalled(), which returns true if there is some reason to believe that the RCU grace period is stalled. The use case is where an RCU free-memory path needs to allocate memory in order to free it, a situation that should be avoided where possible. But where it is necessary, there is always the alternative of using synchronize_rcu() to wait for a grace period in order to avoid the allocation. And if the grace period is stalled, allocating memory to asynchronously wait for it is a bad idea of epic proportions: Far better to let others use the memory, because these others might actually be able to free that memory before the grace period ends. Thus, rcu_gp_might_be_stalled() can be used to help decide whether allocating memory on an RCU free path is a semi-reasonable course of action. Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Uladzislau Rezki <urezki@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
73 lines
2.1 KiB
C
73 lines
2.1 KiB
C
/* SPDX-License-Identifier: GPL-2.0+ */
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/*
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* Read-Copy Update mechanism for mutual exclusion (tree-based version)
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*
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* Copyright IBM Corporation, 2008
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*
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* Author: Dipankar Sarma <dipankar@in.ibm.com>
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* Paul E. McKenney <paulmck@linux.ibm.com> Hierarchical algorithm
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*
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* Based on the original work by Paul McKenney <paulmck@linux.ibm.com>
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* and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
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*
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* For detailed explanation of Read-Copy Update mechanism see -
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* Documentation/RCU
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*/
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#ifndef __LINUX_RCUTREE_H
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#define __LINUX_RCUTREE_H
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void rcu_softirq_qs(void);
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void rcu_note_context_switch(bool preempt);
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int rcu_needs_cpu(u64 basem, u64 *nextevt);
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void rcu_cpu_stall_reset(void);
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/*
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* Note a virtualization-based context switch. This is simply a
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* wrapper around rcu_note_context_switch(), which allows TINY_RCU
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* to save a few bytes. The caller must have disabled interrupts.
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*/
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static inline void rcu_virt_note_context_switch(int cpu)
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{
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rcu_note_context_switch(false);
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}
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void synchronize_rcu_expedited(void);
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void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func);
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void rcu_barrier(void);
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bool rcu_eqs_special_set(int cpu);
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void rcu_momentary_dyntick_idle(void);
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void kfree_rcu_scheduler_running(void);
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bool rcu_gp_might_be_stalled(void);
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unsigned long get_state_synchronize_rcu(void);
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void cond_synchronize_rcu(unsigned long oldstate);
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void rcu_idle_enter(void);
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void rcu_idle_exit(void);
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void rcu_irq_enter(void);
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void rcu_irq_exit(void);
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void rcu_irq_enter_irqson(void);
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void rcu_irq_exit_irqson(void);
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void exit_rcu(void);
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void rcu_scheduler_starting(void);
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extern int rcu_scheduler_active __read_mostly;
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void rcu_end_inkernel_boot(void);
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bool rcu_inkernel_boot_has_ended(void);
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bool rcu_is_watching(void);
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#ifndef CONFIG_PREEMPTION
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void rcu_all_qs(void);
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#endif
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/* RCUtree hotplug events */
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int rcutree_prepare_cpu(unsigned int cpu);
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int rcutree_online_cpu(unsigned int cpu);
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int rcutree_offline_cpu(unsigned int cpu);
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int rcutree_dead_cpu(unsigned int cpu);
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int rcutree_dying_cpu(unsigned int cpu);
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void rcu_cpu_starting(unsigned int cpu);
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#endif /* __LINUX_RCUTREE_H */
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