#include <errno.h>
#include <poll.h>
-#include "urcu/wfqueue.h"
+#include "urcu/wfcqueue.h"
#include "urcu/map/urcu-qsbr.h"
#define BUILD_QSBR_LIB
#include "urcu/static/urcu-qsbr.h"
static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER;
-int32_t gp_futex;
+int32_t rcu_gp_futex;
/*
* Global grace period counter.
DEFINE_URCU_TLS(struct rcu_reader, rcu_reader);
#ifdef DEBUG_YIELD
-unsigned int yield_active;
-DEFINE_URCU_TLS(unsigned int, rand_yield);
+unsigned int rcu_yield_active;
+DEFINE_URCU_TLS(unsigned int, rcu_rand_yield);
#endif
static CDS_LIST_HEAD(registry);
{
/* Read reader_gp before read futex */
cmm_smp_rmb();
- if (uatomic_read(&gp_futex) == -1)
- futex_noasync(&gp_futex, FUTEX_WAIT, -1,
+ if (uatomic_read(&rcu_gp_futex) == -1)
+ futex_noasync(&rcu_gp_futex, FUTEX_WAIT, -1,
NULL, NULL, 0);
}
-static void update_counter_and_wait(void)
+static void wait_for_readers(struct cds_list_head *input_readers,
+ struct cds_list_head *cur_snap_readers,
+ struct cds_list_head *qsreaders)
{
- CDS_LIST_HEAD(qsreaders);
int wait_loops = 0;
struct rcu_reader *index, *tmp;
-#if (CAA_BITS_PER_LONG < 64)
- /* Switch parity: 0 -> 1, 1 -> 0 */
- CMM_STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR);
-#else /* !(CAA_BITS_PER_LONG < 64) */
- /* Increment current G.P. */
- CMM_STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr + RCU_GP_CTR);
-#endif /* !(CAA_BITS_PER_LONG < 64) */
-
- /*
- * Must commit rcu_gp_ctr update to memory before waiting for
- * quiescent state. Failure to do so could result in the writer
- * waiting forever while new readers are always accessing data
- * (no progress). Enforce compiler-order of store to rcu_gp_ctr
- * before load URCU_TLS(rcu_reader).ctr.
- */
- cmm_barrier();
-
- /*
- * Adding a cmm_smp_mb() which is _not_ formally required, but makes the
- * model easier to understand. It does not have a big performance impact
- * anyway, given this is the write-side.
- */
- cmm_smp_mb();
-
/*
- * Wait for each thread rcu_reader_qs_gp count to become 0.
+ * Wait for each thread URCU_TLS(rcu_reader).ctr to either
+ * indicate quiescence (offline), or for them to observe the
+ * current rcu_gp_ctr value.
*/
for (;;) {
wait_loops++;
if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) {
- uatomic_set(&gp_futex, -1);
+ uatomic_set(&rcu_gp_futex, -1);
/*
* Write futex before write waiting (the other side
* reads them in the opposite order).
*/
cmm_smp_wmb();
- cds_list_for_each_entry(index, ®istry, node) {
+ cds_list_for_each_entry(index, input_readers, node) {
_CMM_STORE_SHARED(index->waiting, 1);
}
/* Write futex before read reader_gp */
cmm_smp_mb();
}
- cds_list_for_each_entry_safe(index, tmp, ®istry, node) {
- if (!rcu_gp_ongoing(&index->ctr))
- cds_list_move(&index->node, &qsreaders);
+ cds_list_for_each_entry_safe(index, tmp, input_readers, node) {
+ switch (rcu_reader_state(&index->ctr)) {
+ case RCU_READER_ACTIVE_CURRENT:
+ if (cur_snap_readers) {
+ cds_list_move(&index->node,
+ cur_snap_readers);
+ break;
+ }
+ /* Fall-through */
+ case RCU_READER_INACTIVE:
+ cds_list_move(&index->node, qsreaders);
+ break;
+ case RCU_READER_ACTIVE_OLD:
+ /*
+ * Old snapshot. Leaving node in
+ * input_readers will make us busy-loop
+ * until the snapshot becomes current or
+ * the reader becomes inactive.
+ */
+ break;
+ }
}
- if (cds_list_empty(®istry)) {
+ if (cds_list_empty(input_readers)) {
if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) {
/* Read reader_gp before write futex */
cmm_smp_mb();
- uatomic_set(&gp_futex, 0);
+ uatomic_set(&rcu_gp_futex, 0);
}
break;
} else {
}
}
}
- /* put back the reader list in the registry */
- cds_list_splice(&qsreaders, ®istry);
}
/*
#if (CAA_BITS_PER_LONG < 64)
void synchronize_rcu(void)
{
+ CDS_LIST_HEAD(cur_snap_readers);
+ CDS_LIST_HEAD(qsreaders);
unsigned long was_online;
was_online = URCU_TLS(rcu_reader).ctr;
goto out;
/*
- * Wait for previous parity to be empty of readers.
+ * Wait for readers to observe original parity or be quiescent.
*/
- update_counter_and_wait(); /* 0 -> 1, wait readers in parity 0 */
+ wait_for_readers(®istry, &cur_snap_readers, &qsreaders);
/*
- * Must finish waiting for quiescent state for parity 0 before
- * committing next rcu_gp_ctr update to memory. Failure to
- * do so could result in the writer waiting forever while new
+ * Must finish waiting for quiescent state for original parity
+ * before committing next rcu_gp_ctr update to memory. Failure
+ * to do so could result in the writer waiting forever while new
* readers are always accessing data (no progress). Enforce
- * compiler-order of load URCU_TLS(rcu_reader).ctr before store to
- * rcu_gp_ctr.
+ * compiler-order of load URCU_TLS(rcu_reader).ctr before store
+ * to rcu_gp_ctr.
+ */
+ cmm_barrier();
+
+ /*
+ * Adding a cmm_smp_mb() which is _not_ formally required, but makes the
+ * model easier to understand. It does not have a big performance impact
+ * anyway, given this is the write-side.
+ */
+ cmm_smp_mb();
+
+ /* Switch parity: 0 -> 1, 1 -> 0 */
+ CMM_STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR);
+
+ /*
+ * Must commit rcu_gp_ctr update to memory before waiting for
+ * quiescent state. Failure to do so could result in the writer
+ * waiting forever while new readers are always accessing data
+ * (no progress). Enforce compiler-order of store to rcu_gp_ctr
+ * before load URCU_TLS(rcu_reader).ctr.
*/
cmm_barrier();
cmm_smp_mb();
/*
- * Wait for previous parity to be empty of readers.
+ * Wait for readers to observe new parity or be quiescent.
+ */
+ wait_for_readers(&cur_snap_readers, NULL, &qsreaders);
+
+ /*
+ * Put quiescent reader list back into registry.
*/
- update_counter_and_wait(); /* 1 -> 0, wait readers in parity 1 */
+ cds_list_splice(&qsreaders, ®istry);
out:
mutex_unlock(&rcu_gp_lock);
#else /* !(CAA_BITS_PER_LONG < 64) */
void synchronize_rcu(void)
{
+ CDS_LIST_HEAD(qsreaders);
unsigned long was_online;
was_online = URCU_TLS(rcu_reader).ctr;
mutex_lock(&rcu_gp_lock);
if (cds_list_empty(®istry))
goto out;
- update_counter_and_wait();
+
+ /* Increment current G.P. */
+ CMM_STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr + RCU_GP_CTR);
+
+ /*
+ * Must commit rcu_gp_ctr update to memory before waiting for
+ * quiescent state. Failure to do so could result in the writer
+ * waiting forever while new readers are always accessing data
+ * (no progress). Enforce compiler-order of store to rcu_gp_ctr
+ * before load URCU_TLS(rcu_reader).ctr.
+ */
+ cmm_barrier();
+
+ /*
+ * Adding a cmm_smp_mb() which is _not_ formally required, but makes the
+ * model easier to understand. It does not have a big performance impact
+ * anyway, given this is the write-side.
+ */
+ cmm_smp_mb();
+
+ /*
+ * Wait for readers to observe new count of be quiescent.
+ */
+ wait_for_readers(®istry, NULL, &qsreaders);
+
+ /*
+ * Put quiescent reader list back into registry.
+ */
+ cds_list_splice(&qsreaders, ®istry);
out:
mutex_unlock(&rcu_gp_lock);
projects / urcu.git / blobdiff