autotools/siteinfo: Tweak CONFIG_SITE handling for determism/races

As things stand there are multiple races in the CONFIG_SITE handling
where checksums can change depending on whether site directories
exist or not when parsing happens. This is bad.

Secondly, there is a build race that occurs if you build virtuals
in parallel with the "main" recipe, since the main recipe is parsed
when the virtual is (since it sets variables like BBCLASSEXTEND)
and with the current code, it may look for files and directories
which could be created/destroyed which the loop is executing. This
is also bad.

The aclocal-copy directory should only ever be accessed by the call
from autotools.bbclass. This changes the parameter name to make it
clear and ensures all callers have the right usage, neatly avoiding
all the problems above. Also added better comments.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

3 files changed, 16 insertions, 10 deletions

diff --git a/meta/classes/autotools.bbclass b/meta/classes/autotools.bbclass
index 4c32c84fa8..e5f527ec07 100644
--- a/meta/classes/autotools.bbclass
+++ b/meta/classes/autotools.bbclass
@@ -25,7 +25,7 @@ inherit siteinfo
 
 # Space separated list of shell scripts with variables defined to supply test
 # results for autoconf tests we cannot run at build time.
-export CONFIG_SITE = "${@siteinfo_get_files(d, False)}"
+export CONFIG_SITE = "${@siteinfo_get_files(d)}"
 
 acpaths = "default"
 EXTRA_AUTORECONF = "--exclude=autopoint"
@@ -253,8 +253,9 @@ python autotools_copy_aclocals () {
         t = os.path.join(aclocaldir, os.path.basename(c))
         if not os.path.exists(t):
             os.symlink(c, t)
-            
-    d.setVar("CONFIG_SITE", siteinfo_get_files(d, False))
+
+    # Refresh variable with cache files
+    d.setVar("CONFIG_SITE", siteinfo_get_files(d, aclocalcache=True))
 }
 autotools_copy_aclocals[vardepsexclude] += "MACHINE SDK_ARCH BUILD_ARCH SDK_OS BB_TASKDEPDATA"
 
diff --git a/meta/classes/siteinfo.bbclass b/meta/classes/siteinfo.bbclass
index 03d4c4fd20..6a2e4bf560 100644
--- a/meta/classes/siteinfo.bbclass
+++ b/meta/classes/siteinfo.bbclass
@@ -153,7 +153,7 @@ python () {
         bb.fatal("Please add your architecture to siteinfo.bbclass")
 }
 
-def siteinfo_get_files(d, no_cache = False):
+def siteinfo_get_files(d, aclocalcache = False):
     sitedata = siteinfo_data(d)
     sitefiles = ""
     for path in d.getVar("BBPATH", True).split(":"):
@@ -162,11 +162,17 @@ def siteinfo_get_files(d, no_cache = False):
             if os.path.exists(filename):
                 sitefiles += filename + " "
 
-    if no_cache: return sitefiles
+    if not aclocalcache:
+        return sitefiles
 
-    # Now check for siteconfig cache files
-    # Use the files copied to the aclocal cache generated by autotools.bbclass
-    # to avoid races
+    # Now check for siteconfig cache files in the directory setup by autotools.bbclass to
+    # avoid races.
+    #
+    # ACLOCALDIR may or may not exist so cache should only be set to True from autotools.bbclass
+    # after files have been copied into this location. To do otherwise risks parsing/signature
+    # issues and the directory being created/removed whilst this code executes. This can happen
+    # when a multilib recipe is parsed along with its base variant which may be running at the time
+    # causing rare but nasty failures
     path_siteconfig = d.getVar('ACLOCALDIR', True)
     if path_siteconfig and os.path.isdir(path_siteconfig):
         for i in os.listdir(path_siteconfig):
@@ -174,7 +180,6 @@ def siteinfo_get_files(d, no_cache = False):
                 continue
             filename = os.path.join(path_siteconfig, i)
             sitefiles += filename + " "
-
     return sitefiles
 
 #
diff --git a/meta/classes/toolchain-scripts.bbclass b/meta/classes/toolchain-scripts.bbclass
index 57874f38dc..997ff8865f 100644
--- a/meta/classes/toolchain-scripts.bbclass
+++ b/meta/classes/toolchain-scripts.bbclass
@@ -105,7 +105,7 @@ EOF
 }
 
 #we get the cached site config in the runtime
-TOOLCHAIN_CONFIGSITE_NOCACHE = "${@siteinfo_get_files(d, True)}"
+TOOLCHAIN_CONFIGSITE_NOCACHE = "${@siteinfo_get_files(d)}"
 TOOLCHAIN_CONFIGSITE_SYSROOTCACHE = "${STAGING_DIR}/${MLPREFIX}${MACHINE}/${target_datadir}/${TARGET_SYS}_config_site.d"
 TOOLCHAIN_NEED_CONFIGSITE_CACHE ??= "virtual/${MLPREFIX}libc ncurses"