urcu-wait: move wait code into separate file
authorMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Sun, 18 Nov 2012 20:16:43 +0000 (15:16 -0500)
committerMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Wed, 5 Dec 2012 10:48:00 +0000 (05:48 -0500)
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Makefile.am
urcu-qsbr.c
urcu-wait.h [new file with mode: 0644]

index 195b89af6b18a564fe3185a7075d138a8c2013ba..0a4d357a846b6f628fa279437609d4d8f6eccc1e 100644 (file)
@@ -23,7 +23,7 @@ nobase_dist_include_HEADERS = urcu/compiler.h urcu/hlist.h urcu/list.h \
                urcu/tls-compat.h
 nobase_nodist_include_HEADERS = urcu/arch.h urcu/uatomic.h urcu/config.h
 
-dist_noinst_HEADERS = urcu-die.h
+dist_noinst_HEADERS = urcu-die.h urcu-wait.h
 
 EXTRA_DIST = $(top_srcdir)/urcu/arch/*.h $(top_srcdir)/urcu/uatomic/*.h \
                gpl-2.0.txt lgpl-2.1.txt lgpl-relicensing.txt \
index 7f747ed5f9ce8ef133df3c2d026b8b76154e2e9e..d69138974722d881d9345a105f48a6c4870d8f45 100644 (file)
@@ -44,6 +44,7 @@
 #include "urcu/tls-compat.h"
 
 #include "urcu-die.h"
+#include "urcu-wait.h"
 
 /* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */
 #undef _LGPL_SOURCE
@@ -79,24 +80,9 @@ DEFINE_URCU_TLS(unsigned int, rcu_rand_yield);
 
 static CDS_LIST_HEAD(registry);
 
-/*
- * Number of busy-loop attempts before waiting on futex for grace period
- * batching.
- */
-#define RCU_AWAKE_ATTEMPTS 1000
-
-enum adapt_wakeup_state {
-       /* AWAKE_WAITING is compared directly (futex compares it). */
-       AWAKE_WAITING =         0,
-       /* non-zero are used as masks. */
-       AWAKE_WAKEUP =          (1 << 0),
-       AWAKE_AWAKENED =        (1 << 1),
-       AWAKE_TEARDOWN =        (1 << 2),
-};
-
 struct gp_waiters_thread {
        struct cds_wfs_node node;
-       int32_t wait_futex;
+       struct urcu_wait wait;
 };
 
 /*
@@ -146,58 +132,6 @@ static void wait_gp(void)
                      NULL, NULL, 0);
 }
 
-/*
- * Note: urcu_adaptative_wake_up needs "value" to stay allocated
- * throughout its execution. In this scheme, the waiter owns the futex
- * memory, and we only allow it to free this memory when it receives the
- * AWAKE_TEARDOWN flag.
- */
-static void urcu_adaptative_wake_up(int32_t *value)
-{
-       cmm_smp_mb();
-       assert(uatomic_read(value) == AWAKE_WAITING);
-       uatomic_set(value, AWAKE_WAKEUP);
-       if (!(uatomic_read(value) & AWAKE_AWAKENED))
-               futex_noasync(value, FUTEX_WAKE, 1, NULL, NULL, 0);
-       /* Allow teardown of "value" memory. */
-       uatomic_or(value, AWAKE_TEARDOWN);
-}
-
-/*
- * Caller must initialize "value" to AWAKE_WAITING before passing its
- * memory to waker thread.
- */
-static void urcu_adaptative_busy_wait(int32_t *value)
-{
-       unsigned int i;
-
-       /* Load and test condition before read futex */
-       cmm_smp_rmb();
-       for (i = 0; i < RCU_AWAKE_ATTEMPTS; i++) {
-               if (uatomic_read(value) != AWAKE_WAITING)
-                       goto skip_futex_wait;
-               caa_cpu_relax();
-       }
-       futex_noasync(value, FUTEX_WAIT, AWAKE_WAITING, NULL, NULL, 0);
-skip_futex_wait:
-
-       /* Tell waker thread than we are awakened. */
-       uatomic_or(value, AWAKE_AWAKENED);
-
-       /*
-        * Wait until waker thread lets us know it's ok to tear down
-        * memory allocated for value.
-        */
-       for (i = 0; i < RCU_AWAKE_ATTEMPTS; i++) {
-               if (uatomic_read(value) & AWAKE_TEARDOWN)
-                       break;
-               caa_cpu_relax();
-       }
-       while (!(uatomic_read(value) & AWAKE_TEARDOWN))
-               poll(NULL, 0, 10);
-       assert(uatomic_read(value) & AWAKE_TEARDOWN);
-}
-
 static void wait_for_readers(struct cds_list_head *input_readers,
                        struct cds_list_head *cur_snap_readers,
                        struct cds_list_head *qsreaders)
@@ -305,10 +239,10 @@ void synchronize_rcu(void)
         * if we are the first thread added into the stack.
         */
        cds_wfs_node_init(&gp_waiters_thread.node);
-       gp_waiters_thread.wait_futex = AWAKE_WAITING;
+       urcu_wait_init(&gp_waiters_thread.wait);
        if (cds_wfs_push(&gp_waiters, &gp_waiters_node) != 0) {
                /* Not first in stack: will be awakened by another thread. */
-               urcu_adaptative_busy_wait(&gp_waiters_thread.wait_futex);
+               urcu_adaptative_busy_wait(&gp_waiters_thread.wait);
                goto gp_end;
        }
 
@@ -384,7 +318,7 @@ out:
                                struct gp_waiters_thread, node);
                if (wt == &gp_waiters_thread)
                        continue;
-               urcu_adaptative_wake_up(&wt->wait_futex);
+               urcu_adaptative_wake_up(&wt->wait);
        }
 
 gp_end:
@@ -424,10 +358,10 @@ void synchronize_rcu(void)
         * if we are the first thread added into the stack.
         */
        cds_wfs_node_init(&gp_waiters_thread.node);
-       gp_waiters_thread.wait_futex = AWAKE_WAITING;
+       urcu_wait_init(&gp_waiters_thread.wait);
        if (cds_wfs_push(&gp_waiters, &gp_waiters_thread.node) != 0) {
                /* Not first in stack: will be awakened by another thread. */
-               urcu_adaptative_busy_wait(&gp_waiters_thread.wait_futex);
+               urcu_adaptative_busy_wait(&gp_waiters_thread.wait);
                goto gp_end;
        }
 
@@ -481,7 +415,7 @@ out:
                                struct gp_waiters_thread, node);
                if (wt == &gp_waiters_thread)
                        continue;
-               urcu_adaptative_wake_up(&wt->wait_futex);
+               urcu_adaptative_wake_up(&wt->wait);
        }
 
 gp_end:
diff --git a/urcu-wait.h b/urcu-wait.h
new file mode 100644 (file)
index 0000000..13f26cc
--- /dev/null
@@ -0,0 +1,107 @@
+#ifndef _URCU_WAIT_H
+#define _URCU_WAIT_H
+
+/*
+ * urcu-wait.h
+ *
+ * Userspace RCU library wait/wakeup management
+ *
+ * Copyright (c) 2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <urcu/uatomic.h>
+
+/*
+ * Number of busy-loop attempts before waiting on futex for grace period
+ * batching.
+ */
+#define URCU_WAIT_ATTEMPTS 1000
+
+enum urcu_wait_state {
+       /* URCU_WAIT_WAITING is compared directly (futex compares it). */
+       URCU_WAIT_WAITING =     0,
+       /* non-zero are used as masks. */
+       URCU_WAIT_WAKEUP =      (1 << 0),
+       URCU_WAIT_AWAKENED =    (1 << 1),
+       URCU_WAIT_TEARDOWN =    (1 << 2),
+};
+
+struct urcu_wait {
+       int32_t futex;
+};
+
+static inline
+void urcu_wait_init(struct urcu_wait *wait)
+{
+       wait->futex = URCU_WAIT_WAITING;
+}
+
+/*
+ * Note: urcu_adaptative_wake_up needs "value" to stay allocated
+ * throughout its execution. In this scheme, the waiter owns the futex
+ * memory, and we only allow it to free this memory when it receives the
+ * URCU_WAIT_TEARDOWN flag.
+ */
+static inline
+void urcu_adaptative_wake_up(struct urcu_wait *wait)
+{
+       cmm_smp_mb();
+       assert(uatomic_read(&wait->futex) == URCU_WAIT_WAITING);
+       uatomic_set(&wait->futex, URCU_WAIT_WAKEUP);
+       if (!(uatomic_read(&wait->futex) & URCU_WAIT_AWAKENED))
+               futex_noasync(&wait->futex, FUTEX_WAKE, 1, NULL, NULL, 0);
+       /* Allow teardown of struct urcu_wait memory. */
+       uatomic_or(&wait->futex, URCU_WAIT_TEARDOWN);
+}
+
+/*
+ * Caller must initialize "value" to URCU_WAIT_WAITING before passing its
+ * memory to waker thread.
+ */
+static void urcu_adaptative_busy_wait(struct urcu_wait *wait)
+{
+       unsigned int i;
+
+       /* Load and test condition before read futex */
+       cmm_smp_rmb();
+       for (i = 0; i < URCU_WAIT_ATTEMPTS; i++) {
+               if (uatomic_read(&wait->futex) != URCU_WAIT_WAITING)
+                       goto skip_futex_wait;
+               caa_cpu_relax();
+       }
+       futex_noasync(&wait->futex, FUTEX_WAIT,
+               URCU_WAIT_WAITING, NULL, NULL, 0);
+skip_futex_wait:
+
+       /* Tell waker thread than we are awakened. */
+       uatomic_or(&wait->futex, URCU_WAIT_AWAKENED);
+
+       /*
+        * Wait until waker thread lets us know it's ok to tear down
+        * memory allocated for struct urcu_wait.
+        */
+       for (i = 0; i < URCU_WAIT_ATTEMPTS; i++) {
+               if (uatomic_read(&wait->futex) & URCU_WAIT_TEARDOWN)
+                       break;
+               caa_cpu_relax();
+       }
+       while (!(uatomic_read(&wait->futex) & URCU_WAIT_TEARDOWN))
+               poll(NULL, 0, 10);
+       assert(uatomic_read(&wait->futex) & URCU_WAIT_TEARDOWN);
+}
+
+#endif /* _URCU_WAIT_H */
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