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d22959aa93
Reported-by: Frederic Weisbecker <frederic@kernel.org> Reported-by: Neeraj Upadhyay <quic_neeraju@quicinc.com> Reported-by: Boqun Feng <boqun.feng@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
634 lines
20 KiB
C
634 lines
20 KiB
C
// SPDX-License-Identifier: GPL-2.0+
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/*
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* RCU segmented callback lists, function definitions
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*
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* Copyright IBM Corporation, 2017
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*
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* Authors: Paul E. McKenney <paulmck@linux.ibm.com>
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*/
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#include <linux/cpu.h>
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#include <linux/interrupt.h>
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#include <linux/kernel.h>
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#include <linux/types.h>
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#include "rcu_segcblist.h"
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/* Initialize simple callback list. */
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void rcu_cblist_init(struct rcu_cblist *rclp)
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{
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rclp->head = NULL;
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rclp->tail = &rclp->head;
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rclp->len = 0;
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}
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/*
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* Enqueue an rcu_head structure onto the specified callback list.
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*/
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void rcu_cblist_enqueue(struct rcu_cblist *rclp, struct rcu_head *rhp)
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{
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*rclp->tail = rhp;
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rclp->tail = &rhp->next;
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WRITE_ONCE(rclp->len, rclp->len + 1);
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}
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/*
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* Flush the second rcu_cblist structure onto the first one, obliterating
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* any contents of the first. If rhp is non-NULL, enqueue it as the sole
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* element of the second rcu_cblist structure, but ensuring that the second
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* rcu_cblist structure, if initially non-empty, always appears non-empty
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* throughout the process. If rdp is NULL, the second rcu_cblist structure
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* is instead initialized to empty.
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*/
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void rcu_cblist_flush_enqueue(struct rcu_cblist *drclp,
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struct rcu_cblist *srclp,
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struct rcu_head *rhp)
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{
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drclp->head = srclp->head;
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if (drclp->head)
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drclp->tail = srclp->tail;
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else
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drclp->tail = &drclp->head;
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drclp->len = srclp->len;
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if (!rhp) {
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rcu_cblist_init(srclp);
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} else {
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rhp->next = NULL;
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srclp->head = rhp;
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srclp->tail = &rhp->next;
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WRITE_ONCE(srclp->len, 1);
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}
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}
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/*
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* Dequeue the oldest rcu_head structure from the specified callback
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* list.
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*/
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struct rcu_head *rcu_cblist_dequeue(struct rcu_cblist *rclp)
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{
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struct rcu_head *rhp;
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rhp = rclp->head;
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if (!rhp)
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return NULL;
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rclp->len--;
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rclp->head = rhp->next;
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if (!rclp->head)
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rclp->tail = &rclp->head;
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return rhp;
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}
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/* Set the length of an rcu_segcblist structure. */
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static void rcu_segcblist_set_len(struct rcu_segcblist *rsclp, long v)
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{
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#ifdef CONFIG_RCU_NOCB_CPU
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atomic_long_set(&rsclp->len, v);
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#else
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WRITE_ONCE(rsclp->len, v);
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#endif
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}
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/* Get the length of a segment of the rcu_segcblist structure. */
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static long rcu_segcblist_get_seglen(struct rcu_segcblist *rsclp, int seg)
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{
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return READ_ONCE(rsclp->seglen[seg]);
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}
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/* Return number of callbacks in segmented callback list by summing seglen. */
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long rcu_segcblist_n_segment_cbs(struct rcu_segcblist *rsclp)
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{
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long len = 0;
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int i;
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for (i = RCU_DONE_TAIL; i < RCU_CBLIST_NSEGS; i++)
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len += rcu_segcblist_get_seglen(rsclp, i);
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return len;
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}
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/* Set the length of a segment of the rcu_segcblist structure. */
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static void rcu_segcblist_set_seglen(struct rcu_segcblist *rsclp, int seg, long v)
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{
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WRITE_ONCE(rsclp->seglen[seg], v);
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}
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/* Increase the numeric length of a segment by a specified amount. */
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static void rcu_segcblist_add_seglen(struct rcu_segcblist *rsclp, int seg, long v)
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{
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WRITE_ONCE(rsclp->seglen[seg], rsclp->seglen[seg] + v);
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}
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/* Move from's segment length to to's segment. */
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static void rcu_segcblist_move_seglen(struct rcu_segcblist *rsclp, int from, int to)
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{
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long len;
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if (from == to)
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return;
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len = rcu_segcblist_get_seglen(rsclp, from);
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if (!len)
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return;
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rcu_segcblist_add_seglen(rsclp, to, len);
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rcu_segcblist_set_seglen(rsclp, from, 0);
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}
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/* Increment segment's length. */
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static void rcu_segcblist_inc_seglen(struct rcu_segcblist *rsclp, int seg)
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{
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rcu_segcblist_add_seglen(rsclp, seg, 1);
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}
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/*
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* Increase the numeric length of an rcu_segcblist structure by the
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* specified amount, which can be negative. This can cause the ->len
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* field to disagree with the actual number of callbacks on the structure.
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* This increase is fully ordered with respect to the callers accesses
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* both before and after.
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*
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* So why on earth is a memory barrier required both before and after
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* the update to the ->len field???
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*
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* The reason is that rcu_barrier() locklessly samples each CPU's ->len
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* field, and if a given CPU's field is zero, avoids IPIing that CPU.
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* This can of course race with both queuing and invoking of callbacks.
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* Failing to correctly handle either of these races could result in
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* rcu_barrier() failing to IPI a CPU that actually had callbacks queued
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* which rcu_barrier() was obligated to wait on. And if rcu_barrier()
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* failed to wait on such a callback, unloading certain kernel modules
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* would result in calls to functions whose code was no longer present in
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* the kernel, for but one example.
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*
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* Therefore, ->len transitions from 1->0 and 0->1 have to be carefully
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* ordered with respect with both list modifications and the rcu_barrier().
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*
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* The queuing case is CASE 1 and the invoking case is CASE 2.
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*
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* CASE 1: Suppose that CPU 0 has no callbacks queued, but invokes
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* call_rcu() just as CPU 1 invokes rcu_barrier(). CPU 0's ->len field
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* will transition from 0->1, which is one of the transitions that must
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* be handled carefully. Without the full memory barriers after the ->len
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* update and at the beginning of rcu_barrier(), the following could happen:
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*
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* CPU 0 CPU 1
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*
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* call_rcu().
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* rcu_barrier() sees ->len as 0.
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* set ->len = 1.
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* rcu_barrier() does nothing.
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* module is unloaded.
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* callback invokes unloaded function!
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*
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* With the full barriers, any case where rcu_barrier() sees ->len as 0 will
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* have unambiguously preceded the return from the racing call_rcu(), which
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* means that this call_rcu() invocation is OK to not wait on. After all,
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* you are supposed to make sure that any problematic call_rcu() invocations
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* happen before the rcu_barrier().
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*
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*
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* CASE 2: Suppose that CPU 0 is invoking its last callback just as
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* CPU 1 invokes rcu_barrier(). CPU 0's ->len field will transition from
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* 1->0, which is one of the transitions that must be handled carefully.
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* Without the full memory barriers before the ->len update and at the
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* end of rcu_barrier(), the following could happen:
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*
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* CPU 0 CPU 1
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*
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* start invoking last callback
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* set ->len = 0 (reordered)
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* rcu_barrier() sees ->len as 0
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* rcu_barrier() does nothing.
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* module is unloaded
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* callback executing after unloaded!
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*
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* With the full barriers, any case where rcu_barrier() sees ->len as 0
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* will be fully ordered after the completion of the callback function,
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* so that the module unloading operation is completely safe.
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*
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*/
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void rcu_segcblist_add_len(struct rcu_segcblist *rsclp, long v)
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{
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#ifdef CONFIG_RCU_NOCB_CPU
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smp_mb__before_atomic(); // Read header comment above.
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atomic_long_add(v, &rsclp->len);
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smp_mb__after_atomic(); // Read header comment above.
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#else
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smp_mb(); // Read header comment above.
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WRITE_ONCE(rsclp->len, rsclp->len + v);
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smp_mb(); // Read header comment above.
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#endif
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}
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/*
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* Increase the numeric length of an rcu_segcblist structure by one.
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* This can cause the ->len field to disagree with the actual number of
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* callbacks on the structure. This increase is fully ordered with respect
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* to the callers accesses both before and after.
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*/
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void rcu_segcblist_inc_len(struct rcu_segcblist *rsclp)
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{
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rcu_segcblist_add_len(rsclp, 1);
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}
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/*
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* Initialize an rcu_segcblist structure.
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*/
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void rcu_segcblist_init(struct rcu_segcblist *rsclp)
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{
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int i;
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BUILD_BUG_ON(RCU_NEXT_TAIL + 1 != ARRAY_SIZE(rsclp->gp_seq));
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BUILD_BUG_ON(ARRAY_SIZE(rsclp->tails) != ARRAY_SIZE(rsclp->gp_seq));
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rsclp->head = NULL;
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for (i = 0; i < RCU_CBLIST_NSEGS; i++) {
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rsclp->tails[i] = &rsclp->head;
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rcu_segcblist_set_seglen(rsclp, i, 0);
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}
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rcu_segcblist_set_len(rsclp, 0);
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rcu_segcblist_set_flags(rsclp, SEGCBLIST_ENABLED);
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}
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/*
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* Disable the specified rcu_segcblist structure, so that callbacks can
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* no longer be posted to it. This structure must be empty.
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*/
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void rcu_segcblist_disable(struct rcu_segcblist *rsclp)
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{
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WARN_ON_ONCE(!rcu_segcblist_empty(rsclp));
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WARN_ON_ONCE(rcu_segcblist_n_cbs(rsclp));
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rcu_segcblist_clear_flags(rsclp, SEGCBLIST_ENABLED);
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}
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/*
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* Mark the specified rcu_segcblist structure as offloaded (or not)
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*/
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void rcu_segcblist_offload(struct rcu_segcblist *rsclp, bool offload)
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{
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if (offload)
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rcu_segcblist_set_flags(rsclp, SEGCBLIST_LOCKING | SEGCBLIST_OFFLOADED);
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else
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rcu_segcblist_clear_flags(rsclp, SEGCBLIST_OFFLOADED);
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}
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/*
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* Does the specified rcu_segcblist structure contain callbacks that
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* are ready to be invoked?
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*/
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bool rcu_segcblist_ready_cbs(struct rcu_segcblist *rsclp)
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{
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return rcu_segcblist_is_enabled(rsclp) &&
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&rsclp->head != READ_ONCE(rsclp->tails[RCU_DONE_TAIL]);
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}
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/*
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* Does the specified rcu_segcblist structure contain callbacks that
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* are still pending, that is, not yet ready to be invoked?
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*/
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bool rcu_segcblist_pend_cbs(struct rcu_segcblist *rsclp)
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{
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return rcu_segcblist_is_enabled(rsclp) &&
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!rcu_segcblist_restempty(rsclp, RCU_DONE_TAIL);
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}
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/*
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* Return a pointer to the first callback in the specified rcu_segcblist
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* structure. This is useful for diagnostics.
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*/
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struct rcu_head *rcu_segcblist_first_cb(struct rcu_segcblist *rsclp)
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{
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if (rcu_segcblist_is_enabled(rsclp))
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return rsclp->head;
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return NULL;
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}
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/*
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* Return a pointer to the first pending callback in the specified
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* rcu_segcblist structure. This is useful just after posting a given
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* callback -- if that callback is the first pending callback, then
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* you cannot rely on someone else having already started up the required
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* grace period.
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*/
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struct rcu_head *rcu_segcblist_first_pend_cb(struct rcu_segcblist *rsclp)
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{
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if (rcu_segcblist_is_enabled(rsclp))
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return *rsclp->tails[RCU_DONE_TAIL];
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return NULL;
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}
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/*
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* Return false if there are no CBs awaiting grace periods, otherwise,
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* return true and store the nearest waited-upon grace period into *lp.
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*/
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bool rcu_segcblist_nextgp(struct rcu_segcblist *rsclp, unsigned long *lp)
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{
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if (!rcu_segcblist_pend_cbs(rsclp))
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return false;
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*lp = rsclp->gp_seq[RCU_WAIT_TAIL];
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return true;
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}
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/*
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* Enqueue the specified callback onto the specified rcu_segcblist
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* structure, updating accounting as needed. Note that the ->len
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* field may be accessed locklessly, hence the WRITE_ONCE().
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* The ->len field is used by rcu_barrier() and friends to determine
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* if it must post a callback on this structure, and it is OK
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* for rcu_barrier() to sometimes post callbacks needlessly, but
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* absolutely not OK for it to ever miss posting a callback.
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*/
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void rcu_segcblist_enqueue(struct rcu_segcblist *rsclp,
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struct rcu_head *rhp)
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{
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rcu_segcblist_inc_len(rsclp);
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rcu_segcblist_inc_seglen(rsclp, RCU_NEXT_TAIL);
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rhp->next = NULL;
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WRITE_ONCE(*rsclp->tails[RCU_NEXT_TAIL], rhp);
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WRITE_ONCE(rsclp->tails[RCU_NEXT_TAIL], &rhp->next);
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}
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/*
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* Entrain the specified callback onto the specified rcu_segcblist at
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* the end of the last non-empty segment. If the entire rcu_segcblist
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* is empty, make no change, but return false.
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*
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* This is intended for use by rcu_barrier()-like primitives, -not-
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* for normal grace-period use. IMPORTANT: The callback you enqueue
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* will wait for all prior callbacks, NOT necessarily for a grace
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* period. You have been warned.
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*/
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bool rcu_segcblist_entrain(struct rcu_segcblist *rsclp,
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struct rcu_head *rhp)
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{
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int i;
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if (rcu_segcblist_n_cbs(rsclp) == 0)
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return false;
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rcu_segcblist_inc_len(rsclp);
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smp_mb(); /* Ensure counts are updated before callback is entrained. */
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rhp->next = NULL;
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for (i = RCU_NEXT_TAIL; i > RCU_DONE_TAIL; i--)
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if (rsclp->tails[i] != rsclp->tails[i - 1])
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break;
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rcu_segcblist_inc_seglen(rsclp, i);
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WRITE_ONCE(*rsclp->tails[i], rhp);
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for (; i <= RCU_NEXT_TAIL; i++)
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WRITE_ONCE(rsclp->tails[i], &rhp->next);
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return true;
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}
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/*
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* Extract only those callbacks ready to be invoked from the specified
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* rcu_segcblist structure and place them in the specified rcu_cblist
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* structure.
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*/
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void rcu_segcblist_extract_done_cbs(struct rcu_segcblist *rsclp,
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struct rcu_cblist *rclp)
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{
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int i;
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if (!rcu_segcblist_ready_cbs(rsclp))
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return; /* Nothing to do. */
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rclp->len = rcu_segcblist_get_seglen(rsclp, RCU_DONE_TAIL);
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*rclp->tail = rsclp->head;
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WRITE_ONCE(rsclp->head, *rsclp->tails[RCU_DONE_TAIL]);
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WRITE_ONCE(*rsclp->tails[RCU_DONE_TAIL], NULL);
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rclp->tail = rsclp->tails[RCU_DONE_TAIL];
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for (i = RCU_CBLIST_NSEGS - 1; i >= RCU_DONE_TAIL; i--)
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if (rsclp->tails[i] == rsclp->tails[RCU_DONE_TAIL])
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WRITE_ONCE(rsclp->tails[i], &rsclp->head);
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rcu_segcblist_set_seglen(rsclp, RCU_DONE_TAIL, 0);
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}
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/*
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* Extract only those callbacks still pending (not yet ready to be
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* invoked) from the specified rcu_segcblist structure and place them in
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* the specified rcu_cblist structure. Note that this loses information
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* about any callbacks that might have been partway done waiting for
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* their grace period. Too bad! They will have to start over.
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*/
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void rcu_segcblist_extract_pend_cbs(struct rcu_segcblist *rsclp,
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struct rcu_cblist *rclp)
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{
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int i;
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if (!rcu_segcblist_pend_cbs(rsclp))
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return; /* Nothing to do. */
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rclp->len = 0;
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*rclp->tail = *rsclp->tails[RCU_DONE_TAIL];
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rclp->tail = rsclp->tails[RCU_NEXT_TAIL];
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WRITE_ONCE(*rsclp->tails[RCU_DONE_TAIL], NULL);
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for (i = RCU_DONE_TAIL + 1; i < RCU_CBLIST_NSEGS; i++) {
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rclp->len += rcu_segcblist_get_seglen(rsclp, i);
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WRITE_ONCE(rsclp->tails[i], rsclp->tails[RCU_DONE_TAIL]);
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rcu_segcblist_set_seglen(rsclp, i, 0);
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}
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}
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/*
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* Insert counts from the specified rcu_cblist structure in the
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* specified rcu_segcblist structure.
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*/
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void rcu_segcblist_insert_count(struct rcu_segcblist *rsclp,
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struct rcu_cblist *rclp)
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{
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rcu_segcblist_add_len(rsclp, rclp->len);
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}
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/*
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* Move callbacks from the specified rcu_cblist to the beginning of the
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* done-callbacks segment of the specified rcu_segcblist.
|
|
*/
|
|
void rcu_segcblist_insert_done_cbs(struct rcu_segcblist *rsclp,
|
|
struct rcu_cblist *rclp)
|
|
{
|
|
int i;
|
|
|
|
if (!rclp->head)
|
|
return; /* No callbacks to move. */
|
|
rcu_segcblist_add_seglen(rsclp, RCU_DONE_TAIL, rclp->len);
|
|
*rclp->tail = rsclp->head;
|
|
WRITE_ONCE(rsclp->head, rclp->head);
|
|
for (i = RCU_DONE_TAIL; i < RCU_CBLIST_NSEGS; i++)
|
|
if (&rsclp->head == rsclp->tails[i])
|
|
WRITE_ONCE(rsclp->tails[i], rclp->tail);
|
|
else
|
|
break;
|
|
rclp->head = NULL;
|
|
rclp->tail = &rclp->head;
|
|
}
|
|
|
|
/*
|
|
* Move callbacks from the specified rcu_cblist to the end of the
|
|
* new-callbacks segment of the specified rcu_segcblist.
|
|
*/
|
|
void rcu_segcblist_insert_pend_cbs(struct rcu_segcblist *rsclp,
|
|
struct rcu_cblist *rclp)
|
|
{
|
|
if (!rclp->head)
|
|
return; /* Nothing to do. */
|
|
|
|
rcu_segcblist_add_seglen(rsclp, RCU_NEXT_TAIL, rclp->len);
|
|
WRITE_ONCE(*rsclp->tails[RCU_NEXT_TAIL], rclp->head);
|
|
WRITE_ONCE(rsclp->tails[RCU_NEXT_TAIL], rclp->tail);
|
|
}
|
|
|
|
/*
|
|
* Advance the callbacks in the specified rcu_segcblist structure based
|
|
* on the current value passed in for the grace-period counter.
|
|
*/
|
|
void rcu_segcblist_advance(struct rcu_segcblist *rsclp, unsigned long seq)
|
|
{
|
|
int i, j;
|
|
|
|
WARN_ON_ONCE(!rcu_segcblist_is_enabled(rsclp));
|
|
if (rcu_segcblist_restempty(rsclp, RCU_DONE_TAIL))
|
|
return;
|
|
|
|
/*
|
|
* Find all callbacks whose ->gp_seq numbers indicate that they
|
|
* are ready to invoke, and put them into the RCU_DONE_TAIL segment.
|
|
*/
|
|
for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++) {
|
|
if (ULONG_CMP_LT(seq, rsclp->gp_seq[i]))
|
|
break;
|
|
WRITE_ONCE(rsclp->tails[RCU_DONE_TAIL], rsclp->tails[i]);
|
|
rcu_segcblist_move_seglen(rsclp, i, RCU_DONE_TAIL);
|
|
}
|
|
|
|
/* If no callbacks moved, nothing more need be done. */
|
|
if (i == RCU_WAIT_TAIL)
|
|
return;
|
|
|
|
/* Clean up tail pointers that might have been misordered above. */
|
|
for (j = RCU_WAIT_TAIL; j < i; j++)
|
|
WRITE_ONCE(rsclp->tails[j], rsclp->tails[RCU_DONE_TAIL]);
|
|
|
|
/*
|
|
* Callbacks moved, so there might be an empty RCU_WAIT_TAIL
|
|
* and a non-empty RCU_NEXT_READY_TAIL. If so, copy the
|
|
* RCU_NEXT_READY_TAIL segment to fill the RCU_WAIT_TAIL gap
|
|
* created by the now-ready-to-invoke segments.
|
|
*/
|
|
for (j = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++, j++) {
|
|
if (rsclp->tails[j] == rsclp->tails[RCU_NEXT_TAIL])
|
|
break; /* No more callbacks. */
|
|
WRITE_ONCE(rsclp->tails[j], rsclp->tails[i]);
|
|
rcu_segcblist_move_seglen(rsclp, i, j);
|
|
rsclp->gp_seq[j] = rsclp->gp_seq[i];
|
|
}
|
|
}
|
|
|
|
/*
|
|
* "Accelerate" callbacks based on more-accurate grace-period information.
|
|
* The reason for this is that RCU does not synchronize the beginnings and
|
|
* ends of grace periods, and that callbacks are posted locally. This in
|
|
* turn means that the callbacks must be labelled conservatively early
|
|
* on, as getting exact information would degrade both performance and
|
|
* scalability. When more accurate grace-period information becomes
|
|
* available, previously posted callbacks can be "accelerated", marking
|
|
* them to complete at the end of the earlier grace period.
|
|
*
|
|
* This function operates on an rcu_segcblist structure, and also the
|
|
* grace-period sequence number seq at which new callbacks would become
|
|
* ready to invoke. Returns true if there are callbacks that won't be
|
|
* ready to invoke until seq, false otherwise.
|
|
*/
|
|
bool rcu_segcblist_accelerate(struct rcu_segcblist *rsclp, unsigned long seq)
|
|
{
|
|
int i, j;
|
|
|
|
WARN_ON_ONCE(!rcu_segcblist_is_enabled(rsclp));
|
|
if (rcu_segcblist_restempty(rsclp, RCU_DONE_TAIL))
|
|
return false;
|
|
|
|
/*
|
|
* Find the segment preceding the oldest segment of callbacks
|
|
* whose ->gp_seq[] completion is at or after that passed in via
|
|
* "seq", skipping any empty segments. This oldest segment, along
|
|
* with any later segments, can be merged in with any newly arrived
|
|
* callbacks in the RCU_NEXT_TAIL segment, and assigned "seq"
|
|
* as their ->gp_seq[] grace-period completion sequence number.
|
|
*/
|
|
for (i = RCU_NEXT_READY_TAIL; i > RCU_DONE_TAIL; i--)
|
|
if (rsclp->tails[i] != rsclp->tails[i - 1] &&
|
|
ULONG_CMP_LT(rsclp->gp_seq[i], seq))
|
|
break;
|
|
|
|
/*
|
|
* If all the segments contain callbacks that correspond to
|
|
* earlier grace-period sequence numbers than "seq", leave.
|
|
* Assuming that the rcu_segcblist structure has enough
|
|
* segments in its arrays, this can only happen if some of
|
|
* the non-done segments contain callbacks that really are
|
|
* ready to invoke. This situation will get straightened
|
|
* out by the next call to rcu_segcblist_advance().
|
|
*
|
|
* Also advance to the oldest segment of callbacks whose
|
|
* ->gp_seq[] completion is at or after that passed in via "seq",
|
|
* skipping any empty segments.
|
|
*
|
|
* Note that segment "i" (and any lower-numbered segments
|
|
* containing older callbacks) will be unaffected, and their
|
|
* grace-period numbers remain unchanged. For example, if i ==
|
|
* WAIT_TAIL, then neither WAIT_TAIL nor DONE_TAIL will be touched.
|
|
* Instead, the CBs in NEXT_TAIL will be merged with those in
|
|
* NEXT_READY_TAIL and the grace-period number of NEXT_READY_TAIL
|
|
* would be updated. NEXT_TAIL would then be empty.
|
|
*/
|
|
if (rcu_segcblist_restempty(rsclp, i) || ++i >= RCU_NEXT_TAIL)
|
|
return false;
|
|
|
|
/* Accounting: everything below i is about to get merged into i. */
|
|
for (j = i + 1; j <= RCU_NEXT_TAIL; j++)
|
|
rcu_segcblist_move_seglen(rsclp, j, i);
|
|
|
|
/*
|
|
* Merge all later callbacks, including newly arrived callbacks,
|
|
* into the segment located by the for-loop above. Assign "seq"
|
|
* as the ->gp_seq[] value in order to correctly handle the case
|
|
* where there were no pending callbacks in the rcu_segcblist
|
|
* structure other than in the RCU_NEXT_TAIL segment.
|
|
*/
|
|
for (; i < RCU_NEXT_TAIL; i++) {
|
|
WRITE_ONCE(rsclp->tails[i], rsclp->tails[RCU_NEXT_TAIL]);
|
|
rsclp->gp_seq[i] = seq;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
/*
|
|
* Merge the source rcu_segcblist structure into the destination
|
|
* rcu_segcblist structure, then initialize the source. Any pending
|
|
* callbacks from the source get to start over. It is best to
|
|
* advance and accelerate both the destination and the source
|
|
* before merging.
|
|
*/
|
|
void rcu_segcblist_merge(struct rcu_segcblist *dst_rsclp,
|
|
struct rcu_segcblist *src_rsclp)
|
|
{
|
|
struct rcu_cblist donecbs;
|
|
struct rcu_cblist pendcbs;
|
|
|
|
lockdep_assert_cpus_held();
|
|
|
|
rcu_cblist_init(&donecbs);
|
|
rcu_cblist_init(&pendcbs);
|
|
|
|
rcu_segcblist_extract_done_cbs(src_rsclp, &donecbs);
|
|
rcu_segcblist_extract_pend_cbs(src_rsclp, &pendcbs);
|
|
|
|
/*
|
|
* No need smp_mb() before setting length to 0, because CPU hotplug
|
|
* lock excludes rcu_barrier.
|
|
*/
|
|
rcu_segcblist_set_len(src_rsclp, 0);
|
|
|
|
rcu_segcblist_insert_count(dst_rsclp, &donecbs);
|
|
rcu_segcblist_insert_count(dst_rsclp, &pendcbs);
|
|
rcu_segcblist_insert_done_cbs(dst_rsclp, &donecbs);
|
|
rcu_segcblist_insert_pend_cbs(dst_rsclp, &pendcbs);
|
|
|
|
rcu_segcblist_init(src_rsclp);
|
|
}
|