urcu-qsbr: move offline threads to separate list

[urcu.git] / urcu.c

diff --git a/urcu.c b/urcu.c
index a5178c0054bea5f0363b571d542b98b4d6803f9e..2d5c510aa6744418c5557d642b451e0afae415cd 100644 (file)
--- a/urcu.c
+++ b/urcu.c
@@ -36,7 +36,7 @@
 #include <errno.h>
 #include <poll.h>
 
-#include "urcu/wfqueue.h"
+#include "urcu/wfcqueue.h"
 #include "urcu/map/urcu.h"
 #include "urcu/static/urcu.h"
 #include "urcu-pointer.h"
@@ -63,7 +63,7 @@
 
 #ifdef RCU_MEMBARRIER
 static int init_done;
-int has_sys_membarrier;
+int rcu_has_sys_membarrier;
 
 void __attribute__((constructor)) rcu_init(void);
 #endif
@@ -83,7 +83,7 @@ void __attribute__((destructor)) rcu_exit(void);
 
 static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER;
 
-int32_t gp_futex;
+int32_t rcu_gp_futex;
 
 /*
  * Global grace period counter.
@@ -100,8 +100,8 @@ unsigned long rcu_gp_ctr = RCU_GP_COUNT;
 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);
@@ -140,7 +140,7 @@ static void mutex_unlock(pthread_mutex_t *mutex)
 #ifdef RCU_MEMBARRIER
 static void smp_mb_master(int group)
 {
-       if (caa_likely(has_sys_membarrier))
+       if (caa_likely(rcu_has_sys_membarrier))
                membarrier(MEMBARRIER_EXPEDITED);
        else
                cmm_smp_mb();
@@ -210,43 +210,26 @@ static void wait_gp(void)
 {
        /* Read reader_gp before read futex */
        smp_mb_master(RCU_MB_GROUP);
-       if (uatomic_read(&gp_futex) == -1)
-               futex_async(&gp_futex, FUTEX_WAIT, -1,
+       if (uatomic_read(&rcu_gp_futex) == -1)
+               futex_async(&rcu_gp_futex, FUTEX_WAIT, -1,
                      NULL, NULL, 0);
 }
 
-void update_counter_and_wait(void)
+static void wait_for_readers(void)
 {
        CDS_LIST_HEAD(qsreaders);
        int wait_loops = 0;
        struct rcu_reader *index, *tmp;
 
-       /* Switch parity: 0 -> 1, 1 -> 0 */
-       CMM_STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR_PHASE);
-
-       /*
-        * 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 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 URCU_TLS(rcu_reader).ctr count to become 0.
+        * Wait for each thread URCU_TLS(rcu_reader).ctr to either
+        * indicate quiescence (not nested), or observe the current
+        * rcu_gp_ctr value.
         */
        for (;;) {
                wait_loops++;
                if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) {
-                       uatomic_dec(&gp_futex);
+                       uatomic_dec(&rcu_gp_futex);
                        /* Write futex before read reader_gp */
                        smp_mb_master(RCU_MB_GROUP);
                }
@@ -261,7 +244,7 @@ void update_counter_and_wait(void)
                        if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) {
                                /* Read reader_gp before write futex */
                                smp_mb_master(RCU_MB_GROUP);
-                               uatomic_set(&gp_futex, 0);
+                               uatomic_set(&rcu_gp_futex, 0);
                        }
                        break;
                } else {
@@ -280,7 +263,7 @@ void update_counter_and_wait(void)
                        if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) {
                                /* Read reader_gp before write futex */
                                smp_mb_master(RCU_MB_GROUP);
-                               uatomic_set(&gp_futex, 0);
+                               uatomic_set(&rcu_gp_futex, 0);
                        }
                        break;
                } else {
@@ -316,12 +299,12 @@ void synchronize_rcu(void)
        smp_mb_master(RCU_MB_GROUP);
 
        /*
-        * 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();
 
        /*
-        * Must finish waiting for quiescent state for parity 0 before
+        * 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
@@ -336,10 +319,29 @@ void synchronize_rcu(void)
         */
        cmm_smp_mb();
 
+       /* Switch parity: 0 -> 1, 1 -> 0 */
+       CMM_STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR_PHASE);
+
+       /*
+        * 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 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 previous parity to be empty of readers.
+        * Wait for readers to observe new parity or be quiescent.
         */
-       update_counter_and_wait();      /* 1 -> 0, wait readers in parity 1 */
+       wait_for_readers();
 
        /* Finish waiting for reader threads before letting the old ptr being
         * freed. Must be done within rcu_gp_lock because it iterates on reader
@@ -389,7 +391,7 @@ void rcu_init(void)
                return;
        init_done = 1;
        if (!membarrier(MEMBARRIER_EXPEDITED | MEMBARRIER_QUERY))
-               has_sys_membarrier = 1;
+               rcu_has_sys_membarrier = 1;
 }
 #endif