Add '--with-spl-symvers-timeout' option

When checking for the SPL Module.symvers file, a timeout can now be
passed in which will pause the configure step while it waits for this
file to be generated. By default, the configure behavior is unchanged as
a timeout of 0 is used. If a positive number of seconds is passed,
configure will wait that number of seconds for the Module.symvers file
before moving on.

The main motivation for this change was to support parallel execution of
'./configure && make' for the SPL and ZFS packages in preparation of
supporting DKMS based packages.

Signed-off-by: Prakash Surya <[email protected]>

config/kernel.m4

@@ -217,24 +217,45 @@ AC_DEFUN([ZFS_AC_KERNEL], [
 dnl #
 dnl # Detect name used for the additional SPL Module.symvers file.  If one
 dnl # does not exist this is likely because the SPL has been configured
-dnl # but not built.  To allow recursive builds a good guess is made as to
-dnl # what this file will be named based on what it is named in the kernel
-dnl # build products.  This file will first be used at link time so if
-dnl # the guess is wrong the build will fail then.  This unfortunately
-dnl # means the ZFS package does not contain a reliable mechanism to
-dnl # detect symbols exported by the SPL at configure time.
+dnl # but not built.  The '--spl-symvers-timeout' option can be passed
+dnl # to pause here, waiting for the file to appear from a concurrently
+dnl # building SPL package.  If the file does not appear in time, a good
+dnl # guess is made as to what this file will be named based on what it
+dnl # is named in the kernel build products.  This file will first be
+dnl # used at link time so if the guess is wrong the build will fail
+dnl # then.  This unfortunately means the ZFS package does not contain a
+dnl # reliable mechanism to detect symbols exported by the SPL at
+dnl # configure time.
 dnl #
 AC_DEFUN([ZFS_AC_SPL_MODULE_SYMVERS], [
+	AC_ARG_WITH([spl-symvers-timeout],
+		AS_HELP_STRING([--with-spl-symvers-timeout=SECONDS],
+		[Wait SECONDS for spl symvers file to appear (default 0)]),
+		[timeout="$withval"], [timeout=0])
+
 	AC_MSG_CHECKING([spl file name for module symbols])
-	AS_IF([test -r $SPL_OBJ/Module.symvers], [
-		SPL_SYMBOLS=Module.symvers
-	], [test -r $SPL_OBJ/Modules.symvers], [
-		SPL_SYMBOLS=Modules.symvers
-	], [test -r $SPL_OBJ/module/Module.symvers], [
-		SPL_SYMBOLS=Module.symvers
-	], [test -r $SPL_OBJ/module/Modules.symvers], [
-		SPL_SYMBOLS=Modules.symvers
-	], [
+	SPL_SYMBOLS=NONE
+
+	while true; do
+		AS_IF([test -r $SPL_OBJ/Module.symvers], [
+			SPL_SYMBOLS=Module.symvers
+		], [test -r $SPL_OBJ/Modules.symvers], [
+			SPL_SYMBOLS=Modules.symvers
+		], [test -r $SPL_OBJ/module/Module.symvers], [
+			SPL_SYMBOLS=Module.symvers
+		], [test -r $SPL_OBJ/module/Modules.symvers], [
+			SPL_SYMBOLS=Modules.symvers
+		])
+
+		AS_IF([test $SPL_SYMBOLS != NONE -o $timeout -le 0], [
+			break;
+		], [
+			sleep 1
+			timeout=$((timeout-1))
+		])
+	done
+
+	AS_IF([test "$SPL_SYMBOLS" = NONE], [
 		SPL_SYMBOLS=$LINUX_SYMBOLS
 	])