Fix the broken cache more.

Take a look at the nano second in the mtime to figure out
if the cache needs to be updated if available.
and do the mutex lock between scanning and writing a cache
to avoid the conflict.

Also we don't need to scan directories again after writing
caches. so getting rid of the related code as well.

https://bugs.freedesktop.org/show_bug.cgi?id=69845

and for reference:

https://bugzilla.redhat.com/show_bug.cgi?id=1236034

4 files changed, 112 insertions, 2 deletions

diff --git a/src/fcarch.c b/src/fcarch.c
index 4a921c06..da33a83d 100644
--- a/src/fcarch.c
+++ b/src/fcarch.c
@@ -48,7 +48,7 @@ FC_ASSERT_STATIC (0x08 + 1*FC_MAX(SIZEOF_VOID_P,ALIGNOF_DOUBLE) == sizeof (FcVal
 FC_ASSERT_STATIC (0x00 + 2*SIZEOF_VOID_P == sizeof (FcPatternElt));
 FC_ASSERT_STATIC (0x08 + 2*SIZEOF_VOID_P == sizeof (FcPattern));
 FC_ASSERT_STATIC (0x08 + 2*SIZEOF_VOID_P == sizeof (FcCharSet));
-FC_ASSERT_STATIC (0x08 + 6*SIZEOF_VOID_P == sizeof (FcCache));
+FC_ASSERT_STATIC (0x08 + 7*SIZEOF_VOID_P == sizeof (FcCache));
 
 
 int
diff --git a/src/fccache.c b/src/fccache.c
index fc3ed410..20c44180 100644
--- a/src/fccache.c
+++ b/src/fccache.c
@@ -253,6 +253,7 @@ struct _FcCacheSkip {
     dev_t	    cache_dev;
     ino_t	    cache_ino;
     time_t	    cache_mtime;
+    long	    cache_mtime_nano;
     FcCacheSkip	    *next[1];
 };
 
@@ -380,12 +381,18 @@ FcCacheInsert (FcCache *cache, struct stat *cache_stat)
 	s->cache_dev = cache_stat->st_dev;
 	s->cache_ino = cache_stat->st_ino;
 	s->cache_mtime = cache_stat->st_mtime;
+#ifdef HAVE_STRUCT_STAT_ST_MTIM
+	s->cache_mtime_nano = cache_stat->st_mtim.tv_nsec;
+#else
+	s->cache_mtime_nano = 0;
+#endif
     }
     else
     {
 	s->cache_dev = 0;
 	s->cache_ino = 0;
 	s->cache_mtime = 0;
+	s->cache_mtime_nano = 0;
     }
 
     /*
@@ -473,6 +480,10 @@ FcCacheFindByStat (struct stat *cache_stat)
 	    s->cache_ino == cache_stat->st_ino &&
 	    s->cache_mtime == cache_stat->st_mtime)
 	{
+#ifdef HAVE_STRUCT_STAT_ST_MTIM
+	    if (s->cache_mtime != cache_stat->st_mtim.tv_nsec)
+		continue;
+#endif
 	    FcRefInc (&s->ref);
 	    unlock_cache ();
 	    return s->cache;
@@ -540,6 +551,7 @@ static FcBool
 FcCacheTimeValid (FcConfig *config, FcCache *cache, struct stat *dir_stat)
 {
     struct stat	dir_static;
+    FcBool fnano = FcTrue;
 
     if (!dir_stat)
     {
@@ -558,10 +570,18 @@ FcCacheTimeValid (FcConfig *config, FcCache *cache, struct stat *dir_stat)
 	FcStrFree (d);
 	dir_stat = &dir_static;
     }
+#ifdef HAVE_STRUCT_STAT_ST_MTIM
+    fnano = (cache->checksum_nano == dir_stat->st_mtim.tv_nsec);
+    if (FcDebug () & FC_DBG_CACHE)
+	printf ("FcCacheTimeValid dir \"%s\" cache checksum %d.%ld dir checksum %d.%ld\n",
+		FcCacheDir (cache), cache->checksum, cache->checksum_nano, (int) dir_stat->st_mtime, dir_stat->st_mtim.tv_nsec);
+#else
     if (FcDebug () & FC_DBG_CACHE)
 	printf ("FcCacheTimeValid dir \"%s\" cache checksum %d dir checksum %d\n",
 		FcCacheDir (cache), cache->checksum, (int) dir_stat->st_mtime);
-    return cache->checksum == (int) dir_stat->st_mtime;
+#endif
+
+    return cache->checksum == (int) dir_stat->st_mtime && fnano;
 }
 
 static FcBool
@@ -757,6 +777,10 @@ FcDirCacheValidateHelper (FcConfig *config, int fd, struct stat *fd_stat, struct
 	ret = FcFalse;
     else if (c.checksum != (int) dir_stat->st_mtime)
 	ret = FcFalse;
+#ifdef HAVE_STRUCT_STAT_ST_MTIM
+    else if (c.checksum_nano != dir_stat->st_mtim.tv_nsec)
+	ret = FcFalse;
+#endif
     return ret;
 }
 
@@ -831,6 +855,9 @@ FcDirCacheBuild (FcFontSet *set, const FcChar8 *dir, struct stat *dir_stat, FcSt
     cache->version = FC_CACHE_VERSION_NUMBER;
     cache->size = serialize->size;
     cache->checksum = (int) dir_stat->st_mtime;
+#ifdef HAVE_STRUCT_STAT_ST_MTIM
+    cache->checksum_nano = dir_stat->st_mtim.tv_nsec;
+#endif
 
     /*
      * Serialize directory name
@@ -1018,6 +1045,11 @@ FcDirCacheWrite (FcCache *cache, FcConfig *config)
 	    skip->cache_dev = cache_stat.st_dev;
 	    skip->cache_ino = cache_stat.st_ino;
 	    skip->cache_mtime = cache_stat.st_mtime;
+#ifdef HAVE_STRUCT_STAT_ST_MTIM
+	    skip->cache_mtime_nano = cache_stat.st_mtim.tv_nsec;
+#else
+	    skip->cache_mtime_nano = 0;
+#endif
 	}
 	unlock_cache ();
     }
@@ -1142,6 +1174,70 @@ FcDirCacheClean (const FcChar8 *cache_dir, FcBool verbose)
     return ret;
 }
 
+int
+FcDirCacheLock (const FcChar8 *dir,
+		FcConfig      *config)
+{
+    FcChar8 *cache_hashed = NULL;
+    FcChar8 cache_base[CACHEBASE_LEN];
+    FcStrList *list;
+    FcChar8 *cache_dir;
+    const FcChar8 *sysroot = FcConfigGetSysRoot (config);
+    int fd = -1;
+
+    FcDirCacheBasename (dir, cache_base);
+    list = FcStrListCreate (config->cacheDirs);
+    if (!list)
+	return -1;
+
+    while ((cache_dir = FcStrListNext (list)))
+    {
+	if (sysroot)
+	    cache_hashed = FcStrBuildFilename (sysroot, cache_dir, cache_base, NULL);
+	else
+	    cache_hashed = FcStrBuildFilename (cache_dir, cache_base, NULL);
+	if (!cache_hashed)
+	    break;
+	fd = FcOpen ((const char *)cache_hashed, O_RDWR);
+	/* No caches in that directory. simply retry with another one */
+	if (fd != -1)
+	{
+	    struct flock fl;
+
+	    fl.l_type = F_WRLCK;
+	    fl.l_whence = SEEK_SET;
+	    fl.l_start = 0;
+	    fl.l_len = 0;
+	    fl.l_pid = getpid ();
+	    if (fcntl (fd, F_SETLKW, &fl) == -1)
+		goto bail;
+	    break;
+	}
+    }
+    return fd;
+bail:
+    if (fd != -1)
+	close (fd);
+    return -1;
+}
+
+void
+FcDirCacheUnlock (int fd)
+{
+    struct flock fl;
+
+    if (fd != -1)
+    {
+	fl.l_type = F_UNLCK;
+	fl.l_whence = SEEK_SET;
+	fl.l_start = 0;
+	fl.l_len = 0;
+	fl.l_pid = getpid ();
+	fcntl (fd, F_SETLK, &fl);
+	close (fd);
+    }
+}
+
 /*
  * Hokey little macro trick to permit the definitions of C functions
  * with the same name as CPP macros
diff --git a/src/fcdir.c b/src/fcdir.c
index 2e7f0dc7..f4807dd6 100644
--- a/src/fcdir.c
+++ b/src/fcdir.c
@@ -332,6 +332,7 @@ FcDirCacheScan (const FcChar8 *dir, FcConfig *config)
     struct stat		dir_stat;
     const FcChar8	*sysroot = FcConfigGetSysRoot (config);
     FcChar8		*d;
+    int			fd = -1;
 
     if (sysroot)
 	d = FcStrBuildFilename (sysroot, dir, NULL);
@@ -352,6 +353,7 @@ FcDirCacheScan (const FcChar8 *dir, FcConfig *config)
     if (!dirs)
 	goto bail1;
 
+    fd = FcDirCacheLock (dir, config);
     /*
      * Scan the dir
      */
@@ -371,6 +373,7 @@ FcDirCacheScan (const FcChar8 *dir, FcConfig *config)
     FcDirCacheWrite (cache, config);
 
  bail2:
+    FcDirCacheUnlock (fd);
     FcStrSetDestroy (dirs);
  bail1:
     FcFontSetDestroy (set);
@@ -389,6 +392,7 @@ FcDirCacheRescan (const FcChar8 *dir, FcConfig *config)
     FcStrSet *dirs;
     const FcChar8 *sysroot = FcConfigGetSysRoot (config);
     FcChar8 *d = NULL;
+    int fd = -1;
 
     cache = FcDirCacheLoad (dir, config, NULL);
     if (!cache)
@@ -404,6 +408,7 @@ FcDirCacheRescan (const FcChar8 *dir, FcConfig *config)
     if (!dirs)
 	goto bail;
 
+    fd = FcDirCacheLock (dir, config);
     /*
      * Scan the dir
      */
@@ -422,6 +427,7 @@ FcDirCacheRescan (const FcChar8 *dir, FcConfig *config)
     FcDirCacheWrite (new, config);
 
 bail1:
+    FcDirCacheUnlock (fd);
     FcStrSetDestroy (dirs);
 bail:
     if (d)
diff --git a/src/fcint.h b/src/fcint.h
index 15e22fdb..68f98178 100644
--- a/src/fcint.h
+++ b/src/fcint.h
@@ -369,6 +369,7 @@ struct _FcCache {
     int		dirs_count;	    /* number of subdir strings */
     intptr_t	set;		    /* offset to font set */
     int		checksum;	    /* checksum of directory state */
+    long	checksum_nano;	    /* checksum of directory state */
 };
 
 #undef FcCacheDir
@@ -590,6 +591,13 @@ FcCacheFini (void);
 FcPrivate void
 FcDirCacheReference (FcCache *cache, int nref);
 
+FcPrivate int
+FcDirCacheLock (const FcChar8 *dir,
+		FcConfig      *config);
+
+FcPrivate void
+FcDirCacheUnlock (int fd);
+
 /* fccfg.c */
 
 FcPrivate FcBool