Merge the 1.8.x-r1581305 branch:

 * r1581305, r1581315
   Increase timestamp sleep from 1ms to 10ms for hi-res filesystems.
   Justification:
     Missed text changes on some Linux systems.
   Branch:
     ^/subversion/branches/1.8.x-r1581305
   Votes:
     +1: philip, rhuijben, ivan


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/1.8.x@1582588 13f79535-47bb-0310-9956-ffa450edef68

STATUS

@@ -323,15 +323,6 @@ Veto-blocked changes:
 Approved changes:
 =================
 
- * r1581305, r1581315
-   Increase timestamp sleep from 1ms to 10ms for hi-res filesystems.
-   Justification:
-     Missed text changes on some Linux systems.
-   Branch:
-     ^/subversion/branches/1.8.x-r1581305
-   Votes:
-     +1: philip, rhuijben, ivan
-
  * r1555403
    Update copyright years in NOTICE and subversion/libsvn_subr/version.c.
    Justification:

subversion/include/private/svn_dep_compat.h

@@ -114,6 +114,12 @@ typedef apr_uint32_t apr_uintptr_t;
 #define SVN_LOCK_IS_BUSY(x) APR_STATUS_IS_EBUSY(x)
 #endif
 
+#if !APR_VERSION_AT_LEAST(1,4,0)
+#ifndef apr_time_from_msec
+#define apr_time_from_msec(msec) ((apr_time_t)(msec) * 1000)
+#endif
+#endif
+
 /**
  * Check at compile time if the Serf version is at least a certain
  * level.

subversion/libsvn_subr/io.c

@@ -1243,32 +1243,44 @@ svn_io_sleep_for_timestamps(const char *path, apr_pool_t *pool)
         {
           /* Very simplistic but safe approach:
               If the filesystem has < sec mtime we can be reasonably sure
-              that the filesystem has <= millisecond precision.
+              that the filesystem has some sub-second resolution.  On Windows
+              it is likely to be sub-millisecond; on Linux systems it depends
+              on the filesystem, ext4 is typically 1ms, 4ms or 10ms resolution.
 
              ## Perhaps find a better algorithm here. This will fail once
-                in every 1000 cases on a millisecond precision filesystem.
+                in every 1000 cases on a millisecond precision filesystem
+                if the mtime happens to be an exact second.
 
                 But better to fail once in every thousand cases than every
                 time, like we did before.
-                (All tested filesystems I know have at least microsecond precision.)
 
              Note for further research on algorithm:
-               FAT32 has < 1 sec precision on ctime, but 2 sec on mtime */
+               FAT32 has < 1 sec precision on ctime, but 2 sec on mtime.
 
-          /* Sleep for at least 1 millisecond.
-             (t < 1000 will be round to 0 in apr) */
-          apr_sleep(1000);
+               Linux/ext4 with CONFIG_HZ=250 has high resolution
+               apr_time_now and although the filesystem timestamps
+               have similar high precision they are only updated with
+               a coarser 4ms resolution. */
 
-          return;
+          /* 10 milliseconds after now. */
+#ifndef SVN_HI_RES_SLEEP_MS
+#define SVN_HI_RES_SLEEP_MS 10
+#endif
+          then = now + apr_time_from_msec(SVN_HI_RES_SLEEP_MS);
         }
 
-      now = apr_time_now(); /* Extract the time used for the path stat */
-
-      if (now >= then)
-        return; /* Passing negative values may suspend indefinitely (Windows) */
+      /* Remove time taken to do stat() from sleep. */
+      now = apr_time_now();
     }
 
-  apr_sleep(then - now);
+  if (now >= then)
+    return; /* Passing negative values may suspend indefinitely (Windows) */
+
+  /* (t < 1000 will be round to 0 in apr) */
+  if (then - now < 1000)
+    apr_sleep(1000);
+  else
+    apr_sleep(then - now);
 }