/* SPDX-License-Identifier: GPL-2.0+ */
/*
* Read-Copy Update mechanism for mutual exclusion (tree-based version)
* Internal non-public definitions.
*
* Copyright IBM Corporation, 2008
*
* Author: Ingo Molnar <[email protected]>
* Paul E. McKenney <[email protected]>
*/
#include <linux/cache.h>
#include <linux/kthread.h>
#include <linux/spinlock.h>
#include <linux/rtmutex.h>
#include <linux/threads.h>
#include <linux/cpumask.h>
#include <linux/seqlock.h>
#include <linux/swait.h>
#include <linux/rcu_node_tree.h>
#include "rcu_segcblist.h"
/* Communicate arguments to a kthread worker handler. */
struct rcu_exp_work {
unsigned long rew_s;
struct kthread_work rew_work;
};
/* RCU's kthread states for tracing. */
#define RCU_KTHREAD_STOPPED 0
#define RCU_KTHREAD_RUNNING 1
#define RCU_KTHREAD_WAITING 2
#define RCU_KTHREAD_OFFCPU 3
#define RCU_KTHREAD_YIELDING 4
#define RCU_KTHREAD_MAX 4
/*
* Definition for node within the RCU grace-period-detection hierarchy.
*/
struct rcu_node {
raw_spinlock_t __private lock; /* Root rcu_node's lock protects */
/* some rcu_state fields as well as */
/* following. */
unsigned long gp_seq; /* Track rsp->gp_seq. */
unsigned long gp_seq_needed; /* Track furthest future GP request. */
unsigned long completedqs; /* All QSes done for this node. */
unsigned long qsmask; /* CPUs or groups that need to switch in */
/* order for current grace period to proceed.*/
/* In leaf rcu_node, each bit corresponds to */
/* an rcu_data structure, otherwise, each */
/* bit corresponds to a child rcu_node */
/* structure. */
unsigned long rcu_gp_init_mask; /* Mask of offline CPUs at GP init. */
unsigned long qsmaskinit;
/* Per-GP initial value for qsmask. */
/* Initialized from ->qsmaskinitnext at the */
/* beginning of each grace period. */
unsigned long qsmaskinitnext;
unsigned long expmask; /* CPUs or groups that need to check in */
/* to allow the current expedited GP */
/* to complete. */
unsigned long expmaskinit;
/* Per-GP initial values for expmask. */
/* Initialized from ->expmaskinitnext at the */
/* beginning of each expedited GP. */
unsigned long expmaskinitnext;
/* Online CPUs for next expedited GP. */
/* Any CPU that has ever been online will */
/* have its bit set. */
struct kthread_worker *exp_kworker;
/* Workers performing per node expedited GP */
/* initialization. */
unsigned long cbovldmask;
/* CPUs experiencing callback overload. */
unsigned long ffmask; /* Fully functional CPUs. */
unsigned long grpmask; /* Mask to apply to parent qsmask. */
/* Only one bit will be set in this mask. */
int grplo; /* lowest-numbered CPU here. */
int grphi; /* highest-numbered CPU here. */
u8 grpnum; /* group number for next level up. */
u8 level; /* root is at level 0. */
bool wait_blkd_tasks;/* Necessary to wait for blocked tasks to */
/* exit RCU read-side critical sections */
/* before propagating offline up the */
/* rcu_node tree? */
struct rcu_node *parent;
struct list_head blkd_tasks;
/* Tasks blocked in RCU read-side critical */
/* section. Tasks are placed at the head */
/* of this list and age towards the tail. */
struct list_head *gp_tasks;
/* Pointer to the first task blocking the */
/* current grace period, or NULL if there */
/* is no such task. */
struct list_head *exp_tasks;
/* Pointer to the first task blocking the */
/* current expedited grace period, or NULL */
/* if there is no such task. If there */
/* is no current expedited grace period, */
/* then there can cannot be any such task. */
struct list_head *boost_tasks;
/* Pointer to first task that needs to be */
/* priority boosted, or NULL if no priority */
/* boosting is needed for this rcu_node */
/* structure. If there are no tasks */
/* queued on this rcu_node structure that */
/* are blocking the current grace period, */
/* there can be no such task. */
struct rt_mutex boost_mtx;
/* Used only for the priority-boosting */
/* side effect, not as a lock. */
unsigned long boost_time;
/* When to start boosting (jiffies). */
struct mutex kthread_mutex;
/* Exclusion for thread spawning and affinity */
/* manipulation. */
struct task_struct *boost_kthread_task;
/* kthread that takes care of priority */
/* boosting for this rcu_node structure. */
unsigned int boost_kthread_status;
/* State of boost_kthread_task for tracing. */
unsigned long n_boosts; /* Number of boosts for this rcu_node structure. */
#ifdef CONFIG_RCU_NOCB_CPU
struct swait_queue_head nocb_gp_wq[2];
/* Place for rcu_nocb_kthread() to wait GP. */
#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
raw_spinlock_t fqslock ____cacheline_internodealigned_in_smp;
spinlock_t exp_lock ____cacheline_internodealigned_in_smp;
unsigned long exp_seq_rq;
wait_queue_head_t exp_wq[4];
struct rcu_exp_work rew;
bool exp_need_flush; /* Need to flush workitem? */
raw_spinlock_t exp_poll_lock;
/* Lock and data for polled expedited grace periods. */
unsigned long exp_seq_poll_rq;
struct work_struct exp_poll_wq;
} ____cacheline_internodealigned_in_smp;
/*
* Bitmasks in an rcu_node cover the interval [grplo, grphi] of CPU IDs, and
* are indexed relative to this interval rather than the global CPU ID space.
* This generates the bit for a CPU in node-local masks.
*/
#define leaf_node_cpu_bit(rnp, cpu) (BIT((cpu) - (rnp)->grplo))
/*
* Union to allow "aggregate OR" operation on the need for a quiescent
* state by the normal and expedited grace periods.
*/
union rcu_noqs {
struct {
u8 norm;
u8 exp;
} b; /* Bits. */
u16 s; /* Set of bits, aggregate OR here. */
};
/*
* Record the snapshot of the core stats at half of the first RCU stall timeout.
* The member gp_seq is used to ensure that all members are updated only once
* during the sampling period. The snapshot is taken only if this gp_seq is not
* equal to rdp->gp_seq.
*/
struct rcu_snap_record {
unsigned long gp_seq; /* Track rdp->gp_seq counter */
u64 cputime_irq; /* Accumulated cputime of hard irqs */
u64 cputime_softirq;/* Accumulated cputime of soft irqs */
u64 cputime_system; /* Accumulated cputime of kernel tasks */
unsigned long nr_hardirqs; /* Accumulated number of hard irqs */
unsigned int nr_softirqs; /* Accumulated number of soft irqs */
unsigned long long nr_csw; /* Accumulated number of task switches */
unsigned long jiffies; /* Track jiffies value */
};
/* Per-CPU data for read-copy update. */
struct rcu_data {
/* 1) quiescent-state and grace-period handling : */
unsigned long gp_seq; /* Track rsp->gp_seq counter. */
unsigned long gp_seq_needed; /* Track furthest future GP request. */
union rcu_noqs cpu_no_qs; /* No QSes yet for this CPU. */
bool core_needs_qs; /* Core waits for quiescent state. */
bool beenonline; /* CPU online at least once. */
bool gpwrap; /* Possible ->gp_seq wrap. */
bool cpu_started; /* RCU watching this onlining CPU. */
struct rcu_node *mynode; /* This CPU's leaf of hierarchy */
unsigned long grpmask; /* Mask to apply to leaf qsmask. */
unsigned long ticks_this_gp; /* The number of scheduling-clock */
/* ticks this CPU has handled */
/* during and after the last grace */
/* period it is aware of. */
struct irq_work defer_qs_iw; /* Obtain later scheduler attention. */
bool defer_qs_iw_pending; /* Scheduler attention pending? */
struct work_struct strict_work; /* Schedule readers for strict GPs. */
/* 2) batch handling */
struct rcu_segcblist cblist; /* Segmented callback list, with */
/* different callbacks waiting for */
/* different grace periods. */
long qlen_last_fqs_check;
/* qlen at last check for QS forcing */
unsigned long n_cbs_invoked; /* # callbacks invoked since boot. */
unsigned long n_force_qs_snap;
/* did other CPU force QS recently? */
long blimit; /* Upper limit on a processed batch */
/* 3) dynticks interface. */
int watching_snap; /* Per-GP tracking for dynticks. */
bool rcu_need_heavy_qs; /* GP old, so heavy quiescent state! */
bool rcu_urgent_qs; /* GP old need light quiescent state. */
bool rcu_forced_tick; /* Forced tick to provide QS. */
bool rcu_forced_tick_exp; /* ... provide QS to expedited GP. */
/* 4) rcu_barrier(), OOM callbacks, and expediting. */
unsigned long barrier_seq_snap; /* Snap of rcu_state.barrier_sequence. */
struct rcu_head barrier_head;
int exp_watching_snap; /* Double-check need for IPI. */
/* 5) Callback offloading. */
#ifdef CONFIG_RCU_NOCB_CPU
struct swait_queue_head nocb_cb_wq; /* For nocb kthreads to sleep on. */
struct swait_queue_head nocb_state_wq; /* For offloading state changes */
struct task_struct *nocb_gp_kthread;
raw_spinlock_t nocb_lock; /* Guard following pair of fields. */
int nocb_defer_wakeup; /* Defer wakeup of nocb_kthread. */
struct timer_list nocb_timer; /* Enforce finite deferral. */
unsigned long nocb_gp_adv_time; /* Last call_rcu() CB adv (jiffies). */
struct mutex nocb_gp_kthread_mutex; /* Exclusion for nocb gp kthread */
/* spawning */
/* The following fields are used by call_rcu, hence own cacheline. */
raw_spinlock_t nocb_bypass_lock ____cacheline_internodealigned_in_smp;
struct rcu_cblist nocb_bypass; /* Lock-contention-bypass CB list. */
unsigned long nocb_bypass_first; /* Time (jiffies) of first enqueue. */
unsigned long nocb_nobypass_last; /* Last ->cblist enqueue (jiffies). */
int nocb_nobypass_count; /* # ->cblist enqueues at ^^^ time. */
/* The following fields are used by GP kthread, hence own cacheline. */
raw_spinlock_t nocb_gp_lock ____cacheline_internodealigned_in_smp;
u8 nocb_gp_sleep; /* Is the nocb GP thread asleep? */
u8 nocb_gp_bypass; /* Found a bypass on last scan? */
u8 nocb_gp_gp; /* GP to wait for on last scan? */
unsigned long nocb_gp_seq; /* If so, ->gp_seq to wait for. */
unsigned long nocb_gp_loops; /* # passes through wait code. */
struct swait_queue_head nocb_gp_wq; /* For nocb kthreads to sleep on. */
bool nocb_cb_sleep; /* Is the nocb CB thread asleep? */
struct task_struct *nocb_cb_kthread;
struct list_head nocb_head_rdp; /*
* Head of rcu_data list in wakeup chain,
* if rdp_gp.
*/
struct list_head nocb_entry_rdp; /* rcu_data node in wakeup chain. */
struct rcu_data *nocb_toggling_rdp; /* rdp queued for (de-)offloading */
/* The following fields are used by CB kthread, hence new cacheline. */
struct rcu_data *nocb_gp_rdp ____cacheline_internodealigned_in_smp;
/* GP rdp takes GP-end wakeups. */
#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
/* 6) RCU priority boosting. */
struct task_struct *rcu_cpu_kthread_task;
/* rcuc per-CPU kthread or NULL. */
unsigned int rcu_cpu_kthread_status;
char rcu_cpu_has_work;
unsigned long rcuc_activity;
/* 7) Diagnostic data, including RCU CPU stall warnings. */
unsigned int softirq_snap; /* Snapshot of softirq activity. */
/* ->rcu_iw* fields protected by leaf rcu_node ->lock. */
struct irq_work rcu_iw; /* Check for non-irq activity. */
bool rcu_iw_pending; /* Is ->rcu_iw pending? */
unsigned long rcu_iw_gp_seq; /* ->gp_seq associated with ->rcu_iw. */
unsigned long rcu_ofl_gp_seq; /* ->gp_seq at last offline. */
short rcu_ofl_gp_state; /* ->gp_state at last offline. */
unsigned long rcu_onl_gp_seq; /* ->gp_seq at last online. */
short rcu_onl_gp_state; /* ->gp_state at last online. */
unsigned long last_fqs_resched; /* Time of last rcu_resched(). */
unsigned long last_sched_clock; /* Jiffies of last rcu_sched_clock_irq(). */
struct rcu_snap_record snap_record; /* Snapshot of core stats at half of */
/* the first RCU stall timeout */
long lazy_len; /* Length of buffered lazy callbacks. */
int cpu;
};
/* Values for nocb_defer_wakeup field in struct rcu_data. */
#define RCU_NOCB_WAKE_NOT 0
#define RCU_NOCB_WAKE_BYPASS 1
#define RCU_NOCB_WAKE_LAZY 2
#define RCU_NOCB_WAKE 3
#define RCU_NOCB_WAKE_FORCE 4
#define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 250) + (HZ > 500))
/* For jiffies_till_first_fqs and */
/* and jiffies_till_next_fqs. */
#define RCU_JIFFIES_FQS_DIV 256 /* Very large systems need more */
/* delay between bouts of */
/* quiescent-state forcing. */
#define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time to take */
/* at least one scheduling clock */
/* irq before ratting on them. */
#define rcu_wait(cond) \
do { \
for (;;) { \
set_current_state(TASK_INTERRUPTIBLE); \
if (cond) \
break; \
schedule(); \
} \
__set_current_state(TASK_RUNNING); \
} while (0)
/*
* A max threshold for synchronize_rcu() users which are
* awaken directly by the rcu_gp_kthread(). Left part is
* deferred to the main worker.
*/
#define SR_MAX_USERS_WAKE_FROM_GP 5
#define SR_NORMAL_GP_WAIT_HEAD_MAX 5
struct sr_wait_node {
atomic_t inuse;
struct llist_node node;
};
/*
* RCU global state, including node hierarchy. This hierarchy is
* represented in "heap" form in a dense array. The root (first level)
* of the hierarchy is in ->node[0] (referenced by ->level[0]), the second
* level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]),
* and the third level in ->node[m+1] and following (->node[m+1] referenced
* by ->level[2]). The number of levels is determined by the number of
* CPUs and by CONFIG_RCU_FANOUT. Small systems will have a "hierarchy"
* consisting of a single rcu_node.
*/
struct rcu_state {
struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */
struct rcu_node *level[RCU_NUM_LVLS + 1];
/* Hierarchy levels (+1 to */
/* shut bogus gcc warning) */
int ncpus; /* # CPUs seen so far. */
int n_online_cpus; /* # CPUs online for RCU. */
/* The following fields are guarded by the root rcu_node's lock. */
unsigned long gp_seq ____cacheline_internodealigned_in_smp;
/* Grace-period sequence #. */
unsigned long gp_max; /* Maximum GP duration in */
/* jiffies. */
struct task_struct *gp_kthread; /* Task for grace periods. */
struct swait_queue_head gp_wq; /* Where GP task waits. */
short gp_flags; /* Commands for GP task. */
short gp_state; /* GP kthread sleep state. */
unsigned long gp_wake_time; /* Last GP kthread wake. */
unsigned long gp_wake_seq; /* ->gp_seq at ^^^. */
unsigned long gp_seq_polled; /* GP seq for polled API. */
unsigned long gp_seq_polled_snap; /* ->gp_seq_polled at normal GP start. */
unsigned long gp_seq_polled_exp_snap; /* ->gp_seq_polled at expedited GP start. */
/* End of fields guarded by root rcu_node's lock. */
struct mutex barrier_mutex; /* Guards barrier fields. */
atomic_t barrier_cpu_count; /* # CPUs waiting on. */
struct completion barrier_completion; /* Wake at barrier end. */
unsigned long barrier_sequence; /* ++ at start and end of */
/* rcu_barrier(). */
/* End of fields guarded by barrier_mutex. */
raw_spinlock_t barrier_lock; /* Protects ->barrier_seq_snap. */
struct mutex exp_mutex; /* Serialize expedited GP. */
struct mutex exp_wake_mutex; /* Serialize wakeup. */
unsigned long expedited_sequence; /* Take a ticket. */
atomic_t expedited_need_qs; /* # CPUs left to check in. */
struct swait_queue_head expedited_wq; /* Wait for check-ins. */
int ncpus_snap; /* # CPUs seen last time. */
u8 cbovld; /* Callback overload now? */
u8 cbovldnext; /* ^ ^ next time? */
unsigned long jiffies_force_qs; /* Time at which to invoke */
/* force_quiescent_state(). */
unsigned long jiffies_kick_kthreads; /* Time at which to kick */
/* kthreads, if configured. */
unsigned long n_force_qs; /* Number of calls to */
/* force_quiescent_state(). */
unsigned long gp_start; /* Time at which GP started, */
/* but in jiffies. */
unsigned long gp_end; /* Time last GP ended, again */
/* in jiffies. */
unsigned long gp_activity; /* Time of last GP kthread */
/* activity in jiffies. */
unsigned long gp_req_activity; /* Time of last GP request */
/* in jiffies. */
unsigned long jiffies_stall; /* Time at which to check */
/* for CPU stalls. */
int nr_fqs_jiffies_stall; /* Number of fqs loops after
* which read jiffies and set
* jiffies_stall. Stall
* warnings disabled if !0. */
unsigned long jiffies_resched; /* Time at which to resched */
/* a reluctant CPU. */
unsigned long n_force_qs_gpstart; /* Snapshot of n_force_qs at */
/* GP start. */
const char *name; /* Name of structure. */
char abbr; /* Abbreviated name. */
arch_spinlock_t ofl_lock ____cacheline_internodealigned_in_smp;
/* Synchronize offline with */
/* GP pre-initialization. */
/* synchronize_rcu() part. */
struct llist_head srs_next; /* request a GP users. */
struct llist_node *srs_wait_tail; /* wait for GP users. */
struct llist_node *srs_done_tail; /* ready for GP users. */
struct sr_wait_node srs_wait_nodes[SR_NORMAL_GP_WAIT_HEAD_MAX];
struct work_struct srs_cleanup_work;
atomic_t srs_cleanups_pending; /* srs inflight worker cleanups. */
#ifdef CONFIG_RCU_NOCB_CPU
struct mutex nocb_mutex; /* Guards (de-)offloading */
int nocb_is_setup; /* nocb is setup from boot */
#endif
};
/* Values for rcu_state structure's gp_flags field. */
#define RCU_GP_FLAG_INIT 0x1 /* Need grace-period initialization. */
#define RCU_GP_FLAG_FQS 0x2 /* Need grace-period quiescent-state forcing. */
#define RCU_GP_FLAG_OVLD 0x4 /* Experiencing callback overload. */
/* Values for rcu_state structure's gp_state field. */
#define RCU_GP_IDLE 0 /* Initial state and no GP in progress. */
#define RCU_GP_WAIT_GPS 1 /* Wait for grace-period start. */
#define RCU_GP_DONE_GPS 2 /* Wait done for grace-period start. */
#define RCU_GP_ONOFF 3 /* Grace-period initialization hotplug. */
#define RCU_GP_INIT 4 /* Grace-period initialization. */
#define RCU_GP_WAIT_FQS 5 /* Wait for force-quiescent-state time. */
#define RCU_GP_DOING_FQS 6 /* Wait done for force-quiescent-state time. */
#define RCU_GP_CLEANUP 7 /* Grace-period cleanup started. */
#define RCU_GP_CLEANED 8 /* Grace-period cleanup complete. */
/*
* In order to export the rcu_state name to the tracing tools, it
* needs to be added in the __tracepoint_string section.
* This requires defining a separate variable tp_<sname>_varname
* that points to the string being used, and this will allow
* the tracing userspace tools to be able to decipher the string
* address to the matching string.
*/
#ifdef CONFIG_PREEMPT_RCU
#define RCU_ABBR 'p'
#define RCU_NAME_RAW "rcu_preempt"
#else /* #ifdef CONFIG_PREEMPT_RCU */
#define RCU_ABBR 's'
#define RCU_NAME_RAW "rcu_sched"
#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
#ifndef CONFIG_TRACING
#define RCU_NAME RCU_NAME_RAW
#else /* #ifdef CONFIG_TRACING */
static char rcu_name[] = RCU_NAME_RAW;
static const char *tp_rcu_varname __used __tracepoint_string = rcu_name;
#define RCU_NAME rcu_name
#endif /* #else #ifdef CONFIG_TRACING */
/* Forward declarations for tree_plugin.h */
static void rcu_bootup_announce(void);
static void rcu_qs(void);
static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
#ifdef CONFIG_HOTPLUG_CPU
static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
static int rcu_print_task_exp_stall(struct rcu_node *rnp);
static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp);
static void rcu_flavor_sched_clock_irq(int user);
static void dump_blkd_tasks(struct rcu_node *rnp, int ncheck);
static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);
static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
static bool rcu_is_callbacks_kthread(struct rcu_data *rdp);
static void rcu_cpu_kthread_setup(unsigned int cpu);
static void rcu_spawn_one_boost_kthread(struct rcu_node *rnp);
static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
static bool rcu_preempt_need_deferred_qs(struct task_struct *t);
static void zero_cpu_stall_ticks(struct rcu_data *rdp);
static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp);
static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq);
static void rcu_init_one_nocb(struct rcu_node *rnp);
static bool wake_nocb_gp(struct rcu_data *rdp, bool force);
static bool rcu_nocb_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
unsigned long j, bool lazy);
static void call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *head,
rcu_callback_t func, unsigned long flags, bool lazy);
static void __maybe_unused __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_empty,
unsigned long flags);
static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp, int level);
static bool do_nocb_deferred_wakeup(struct rcu_data *rdp);
static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp);
static void rcu_spawn_cpu_nocb_kthread(int cpu);
static void show_rcu_nocb_state(struct rcu_data *rdp);
static void rcu_nocb_lock(struct rcu_data *rdp);
static void rcu_nocb_unlock(struct rcu_data *rdp);
static void rcu_nocb_unlock_irqrestore(struct rcu_data *rdp,
unsigned long flags);
static void rcu_lockdep_assert_cblist_protected(struct rcu_data *rdp);
#ifdef CONFIG_RCU_NOCB_CPU
static void __init rcu_organize_nocb_kthreads(void);
/*
* Disable IRQs before checking offloaded state so that local
* locking is safe against concurrent de-offloading.
*/
#define rcu_nocb_lock_irqsave(rdp, flags) \
do { \
local_irq_save(flags); \
if (rcu_segcblist_is_offloaded(&(rdp)->cblist)) \
raw_spin_lock(&(rdp)->nocb_lock); \
} while (0)
#else /* #ifdef CONFIG_RCU_NOCB_CPU */
#define rcu_nocb_lock_irqsave(rdp, flags) local_irq_save(flags)
#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */
static void rcu_bind_gp_kthread(void);
static bool rcu_nohz_full_cpu(void);
/* Forward declarations for tree_stall.h */
static void record_gp_stall_check_time(void);
static void rcu_iw_handler(struct irq_work *iwp);
static void check_cpu_stall(struct rcu_data *rdp);
static void rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp,
const unsigned long gpssdelay);
/* Forward declarations for tree_exp.h. */
static void sync_rcu_do_polled_gp(struct work_struct *wp);
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