poll-loop: Change poll_timer_wait() parameter from "int" to "long long".

Every so often I get concerned because OVS does most of its time arithmetic
in "long long int" but poll_timer_wait() takes an "int", so there is
potential for truncating a large value to a small value or a positive value
to a negative value.  That would cause excessive wakeups and possibly 100%
CPU usage.

This commit therefore changes poll_timer_wait()'s parameter type from "int"
to "long long int".  The file-scope 'timeout' variable remains type "int"
because that is the type of poll()'s timeout argument.

Factoring poll_timer_wait() into two functions is not necessary here but it
comes in handy in the following patch.

diff --git a/lib/learning-switch.c b/lib/learning-switch.c
index 126cc6b..91f8f05 100644 (file)
--- a/lib/learning-switch.c
+++ b/lib/learning-switch.c
@@ -221,12 +221,7 @@ static void
 wait_timeout(long long int started)
 {
     long long int now = time_msec();
-    long long int timeout = 10000 - (now - started);
-    if (timeout <= 0) {
-        poll_immediate_wake();
-    } else {
-        poll_timer_wait(timeout);
-    }
+    poll_timer_wait(10000 - (now - started));
 }
 
 void

diff --git a/lib/poll-loop.c b/lib/poll-loop.c
index 8f65f94..29931f7 100644 (file)
--- a/lib/poll-loop.c
+++ b/lib/poll-loop.c
@@ -73,6 +73,18 @@ poll_fd_wait(int fd, short int events)
     return new_waiter(fd, events);
 }
 
+/* The caller must ensure that 'msec' is not negative. */
+static void
+poll_timer_wait__(int msec)
+{
+    if (timeout < 0 || msec < timeout) {
+        timeout = msec;
+        if (VLOG_IS_DBG_ENABLED()) {
+            backtrace_capture(&timeout_backtrace);
+        }
+    }
+}
+
 /* Causes the following call to poll_block() to block for no more than 'msec'
  * milliseconds.  If 'msec' is nonpositive, the following call to poll_block()
  * will not block at all.
@@ -81,14 +93,11 @@ poll_fd_wait(int fd, short int events)
  * is affected.  The timer will need to be re-registered after poll_block() is
  * called if it is to persist. */
 void
-poll_timer_wait(int msec)
+poll_timer_wait(long long int msec)
 {
-    if (timeout < 0 || msec < timeout) {
-        timeout = MAX(0, msec);
-        if (VLOG_IS_DBG_ENABLED()) {
-            backtrace_capture(&timeout_backtrace);
-        }
-    }
+    poll_timer_wait__(msec < 0 ? 0
+                      : msec > INT_MAX ? INT_MAX
+                      : msec);
 }
 
 /* Causes the following call to poll_block() to wake up immediately, without

diff --git a/lib/poll-loop.h b/lib/poll-loop.h
index adb88d4..eaeca2b 100644 (file)
--- a/lib/poll-loop.h
+++ b/lib/poll-loop.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008, 2009 Nicira Networks.
+ * Copyright (c) 2008, 2009, 2010 Nicira Networks.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -42,7 +42,7 @@ struct poll_waiter;
 
 /* Schedule events to wake up the following poll_block(). */
 struct poll_waiter *poll_fd_wait(int fd, short int events);
-void poll_timer_wait(int msec);
+void poll_timer_wait(long long int msec);
 void poll_immediate_wake(void);
 
 /* Wait until an event occurs. */

diff --git a/ovsdb/trigger.c b/ovsdb/trigger.c
index 1ecfdca..8f18291 100644 (file)
--- a/ovsdb/trigger.c
+++ b/ovsdb/trigger.c
@@ -1,4 +1,4 @@
-/* Copyright (c) 2009 Nicira Networks
+/* Copyright (c) 2009, 2010 Nicira Networks
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -102,7 +102,7 @@ ovsdb_trigger_wait(struct ovsdb *db, long long int now)
         }
 
         if (deadline < LLONG_MAX) {
-            poll_timer_wait(MIN(deadline - now, INT_MAX));
+            poll_timer_wait(deadline - now);
         }
     }
 }