diff options
Diffstat (limited to 'kernel/rcu/rcu_segcblist.c')
-rw-r--r-- | kernel/rcu/rcu_segcblist.c | 120 |
1 files changed, 77 insertions, 43 deletions
diff --git a/kernel/rcu/rcu_segcblist.c b/kernel/rcu/rcu_segcblist.c index 3cff8003f707..777780447887 100644 --- a/kernel/rcu/rcu_segcblist.c +++ b/kernel/rcu/rcu_segcblist.c @@ -7,10 +7,10 @@ * Authors: Paul E. McKenney <paulmck@linux.ibm.com> */ -#include <linux/types.h> -#include <linux/kernel.h> +#include <linux/cpu.h> #include <linux/interrupt.h> -#include <linux/rcupdate.h> +#include <linux/kernel.h> +#include <linux/types.h> #include "rcu_segcblist.h" @@ -88,6 +88,46 @@ static void rcu_segcblist_set_len(struct rcu_segcblist *rsclp, long v) #endif } +/* Get the length of a segment of the rcu_segcblist structure. */ +static long rcu_segcblist_get_seglen(struct rcu_segcblist *rsclp, int seg) +{ + return READ_ONCE(rsclp->seglen[seg]); +} + +/* Set the length of a segment of the rcu_segcblist structure. */ +static void rcu_segcblist_set_seglen(struct rcu_segcblist *rsclp, int seg, long v) +{ + WRITE_ONCE(rsclp->seglen[seg], v); +} + +/* Increase the numeric length of a segment by a specified amount. */ +static void rcu_segcblist_add_seglen(struct rcu_segcblist *rsclp, int seg, long v) +{ + WRITE_ONCE(rsclp->seglen[seg], rsclp->seglen[seg] + v); +} + +/* Move from's segment length to to's segment. */ +static void rcu_segcblist_move_seglen(struct rcu_segcblist *rsclp, int from, int to) +{ + long len; + + if (from == to) + return; + + len = rcu_segcblist_get_seglen(rsclp, from); + if (!len) + return; + + rcu_segcblist_add_seglen(rsclp, to, len); + rcu_segcblist_set_seglen(rsclp, from, 0); +} + +/* Increment segment's length. */ +static void rcu_segcblist_inc_seglen(struct rcu_segcblist *rsclp, int seg) +{ + rcu_segcblist_add_seglen(rsclp, seg, 1); +} + /* * Increase the numeric length of an rcu_segcblist structure by the * specified amount, which can be negative. This can cause the ->len @@ -180,26 +220,6 @@ void rcu_segcblist_inc_len(struct rcu_segcblist *rsclp) } /* - * Exchange the numeric length of the specified rcu_segcblist structure - * with the specified value. This can cause the ->len field to disagree - * with the actual number of callbacks on the structure. This exchange is - * fully ordered with respect to the callers accesses both before and after. - */ -static long rcu_segcblist_xchg_len(struct rcu_segcblist *rsclp, long v) -{ -#ifdef CONFIG_RCU_NOCB_CPU - return atomic_long_xchg(&rsclp->len, v); -#else - long ret = rsclp->len; - - smp_mb(); /* Up to the caller! */ - WRITE_ONCE(rsclp->len, v); - smp_mb(); /* Up to the caller! */ - return ret; -#endif -} - -/* * Initialize an rcu_segcblist structure. */ void rcu_segcblist_init(struct rcu_segcblist *rsclp) @@ -209,8 +229,10 @@ void rcu_segcblist_init(struct rcu_segcblist *rsclp) BUILD_BUG_ON(RCU_NEXT_TAIL + 1 != ARRAY_SIZE(rsclp->gp_seq)); BUILD_BUG_ON(ARRAY_SIZE(rsclp->tails) != ARRAY_SIZE(rsclp->gp_seq)); rsclp->head = NULL; - for (i = 0; i < RCU_CBLIST_NSEGS; i++) + for (i = 0; i < RCU_CBLIST_NSEGS; i++) { rsclp->tails[i] = &rsclp->head; + rcu_segcblist_set_seglen(rsclp, i, 0); + } rcu_segcblist_set_len(rsclp, 0); rsclp->enabled = 1; } @@ -306,6 +328,7 @@ void rcu_segcblist_enqueue(struct rcu_segcblist *rsclp, { rcu_segcblist_inc_len(rsclp); smp_mb(); /* Ensure counts are updated before callback is enqueued. */ + rcu_segcblist_inc_seglen(rsclp, RCU_NEXT_TAIL); rhp->next = NULL; WRITE_ONCE(*rsclp->tails[RCU_NEXT_TAIL], rhp); WRITE_ONCE(rsclp->tails[RCU_NEXT_TAIL], &rhp->next); @@ -334,6 +357,7 @@ bool rcu_segcblist_entrain(struct rcu_segcblist *rsclp, for (i = RCU_NEXT_TAIL; i > RCU_DONE_TAIL; i--) if (rsclp->tails[i] != rsclp->tails[i - 1]) break; + rcu_segcblist_inc_seglen(rsclp, i); WRITE_ONCE(*rsclp->tails[i], rhp); for (; i <= RCU_NEXT_TAIL; i++) WRITE_ONCE(rsclp->tails[i], &rhp->next); @@ -341,21 +365,6 @@ bool rcu_segcblist_entrain(struct rcu_segcblist *rsclp, } /* - * Extract only the counts from the specified rcu_segcblist structure, - * and place them in the specified rcu_cblist structure. This function - * supports both callback orphaning and invocation, hence the separation - * of counts and callbacks. (Callbacks ready for invocation must be - * orphaned and adopted separately from pending callbacks, but counts - * apply to all callbacks. Locking must be used to make sure that - * both orphaned-callbacks lists are consistent.) - */ -void rcu_segcblist_extract_count(struct rcu_segcblist *rsclp, - struct rcu_cblist *rclp) -{ - rclp->len = rcu_segcblist_xchg_len(rsclp, 0); -} - -/* * Extract only those callbacks ready to be invoked from the specified * rcu_segcblist structure and place them in the specified rcu_cblist * structure. @@ -367,6 +376,7 @@ void rcu_segcblist_extract_done_cbs(struct rcu_segcblist *rsclp, if (!rcu_segcblist_ready_cbs(rsclp)) return; /* Nothing to do. */ + rclp->len = rcu_segcblist_get_seglen(rsclp, RCU_DONE_TAIL); *rclp->tail = rsclp->head; WRITE_ONCE(rsclp->head, *rsclp->tails[RCU_DONE_TAIL]); WRITE_ONCE(*rsclp->tails[RCU_DONE_TAIL], NULL); @@ -374,6 +384,7 @@ void rcu_segcblist_extract_done_cbs(struct rcu_segcblist *rsclp, for (i = RCU_CBLIST_NSEGS - 1; i >= RCU_DONE_TAIL; i--) if (rsclp->tails[i] == rsclp->tails[RCU_DONE_TAIL]) WRITE_ONCE(rsclp->tails[i], &rsclp->head); + rcu_segcblist_set_seglen(rsclp, RCU_DONE_TAIL, 0); } /* @@ -390,11 +401,15 @@ void rcu_segcblist_extract_pend_cbs(struct rcu_segcblist *rsclp, if (!rcu_segcblist_pend_cbs(rsclp)) return; /* Nothing to do. */ + rclp->len = 0; *rclp->tail = *rsclp->tails[RCU_DONE_TAIL]; rclp->tail = rsclp->tails[RCU_NEXT_TAIL]; WRITE_ONCE(*rsclp->tails[RCU_DONE_TAIL], NULL); - for (i = RCU_DONE_TAIL + 1; i < RCU_CBLIST_NSEGS; i++) + for (i = RCU_DONE_TAIL + 1; i < RCU_CBLIST_NSEGS; i++) { + rclp->len += rcu_segcblist_get_seglen(rsclp, i); WRITE_ONCE(rsclp->tails[i], rsclp->tails[RCU_DONE_TAIL]); + rcu_segcblist_set_seglen(rsclp, i, 0); + } } /* @@ -405,7 +420,6 @@ void rcu_segcblist_insert_count(struct rcu_segcblist *rsclp, struct rcu_cblist *rclp) { rcu_segcblist_add_len(rsclp, rclp->len); - rclp->len = 0; } /* @@ -419,6 +433,7 @@ void rcu_segcblist_insert_done_cbs(struct rcu_segcblist *rsclp, 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++) @@ -439,6 +454,8 @@ void rcu_segcblist_insert_pend_cbs(struct rcu_segcblist *rsclp, { 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); } @@ -463,6 +480,7 @@ void rcu_segcblist_advance(struct rcu_segcblist *rsclp, unsigned long seq) 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. */ @@ -483,6 +501,7 @@ void rcu_segcblist_advance(struct rcu_segcblist *rsclp, unsigned long seq) 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]; } } @@ -504,7 +523,7 @@ void rcu_segcblist_advance(struct rcu_segcblist *rsclp, unsigned long seq) */ bool rcu_segcblist_accelerate(struct rcu_segcblist *rsclp, unsigned long seq) { - int i; + int i, j; WARN_ON_ONCE(!rcu_segcblist_is_enabled(rsclp)); if (rcu_segcblist_restempty(rsclp, RCU_DONE_TAIL)) @@ -547,6 +566,10 @@ bool rcu_segcblist_accelerate(struct rcu_segcblist *rsclp, unsigned long seq) 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" @@ -574,13 +597,24 @@ void rcu_segcblist_merge(struct rcu_segcblist *dst_rsclp, struct rcu_cblist donecbs; struct rcu_cblist pendcbs; + lockdep_assert_cpus_held(); + rcu_cblist_init(&donecbs); rcu_cblist_init(&pendcbs); - rcu_segcblist_extract_count(src_rsclp, &donecbs); + 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); } |