ref-manual, dev-manual: Added info about make race work-around

I updated both the PARALLEL_MAKE and PARALLEL_MAKEINST variables
by expanding the note to indicate how to prohibit parallel make
threads.  Also, added a cross-referencing link to the
"Debugging Parallel Make Races" section.

I added a short note to the start of the "Debugging Parallel Make
Races" section noting that if they can't properly fix the condition,
they can always do a work-around to set the PARALLEL_MAKE or
PARALLEL_MAKEINST variables to null.

Reported-by: Robert P. J. Day <rpjday@crashcourse.ca>
(From yocto-docs rev: f8dccf3f115647cb039d91415819186cf38fa8bb)

Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

2 files changed, 29 insertions, 10 deletions

diff --git a/documentation/dev-manual/dev-manual-common-tasks.xml b/documentation/dev-manual/dev-manual-common-tasks.xml
index 1d4e34f91e..bab68a1bb9 100644
--- a/documentation/dev-manual/dev-manual-common-tasks.xml
+++ b/documentation/dev-manual/dev-manual-common-tasks.xml
@@ -9089,6 +9089,14 @@
             you debug and fix them.
             This section presents a real-world example of an error encountered
             on the Yocto Project autobuilder and the process used to fix it.
+            <note>
+                If you cannot properly fix a <filename>make</filename> race
+                condition, you can work around it by clearing either the
+                <ulink url='&YOCTO_DOCS_REF_URL;#var-PARALLEL_MAKE'><filename>PARALLEL_MAKE</filename></ulink>
+                or
+                <ulink url='&YOCTO_DOCS_REF_URL;#var-PARALLEL_MAKEINST'><filename>PARALLEL_MAKEINST</filename></ulink>
+                variables.
+            </note>
         </para>
 
         <section id='the-failure'>
diff --git a/documentation/ref-manual/ref-variables.xml b/documentation/ref-manual/ref-variables.xml
index 27008c7a5d..dfe775b23f 100644
--- a/documentation/ref-manual/ref-variables.xml
+++ b/documentation/ref-manual/ref-variables.xml
@@ -8525,13 +8525,18 @@ recipes-graphics/xorg-font/font-alias_1.0.3.bb:PR = "${INC_PR}.3"
                 </para>
 
                 <para>
-                    The OpenEmbedded build system automatically sets this
-                    variable to be equal to the number of cores the build
-                    system uses.
+                    By default, the OpenEmbedded build system automatically
+                    sets this variable to be equal to the number of cores the
+                    build system uses.
                     <note>
-                        Individual recipes might clear out this variable if
-                        the software being built has problems running its
-                        <filename>make</filename> process in parallel.
+                        If the software being built experiences dependency
+                        issues during the <filename>do_compile</filename>
+                        task that result in race conditions, you can clear
+                        the <filename>PARALLEL_MAKE</filename> variable within
+                        the recipe as a workaround.
+                        For information on addressing race conditions, see the
+                        "<ulink url='&YOCTO_DOCS_DEV_URL;#debugging-parallel-make-races'>Debugging Parallel Make Races</ulink>"
+                        section in the Yocto Project Development Manual.
                     </note>
                     For single socket systems (i.e. one CPU), you should not
                     have to override this variable to gain optimal parallelism
@@ -8539,7 +8544,7 @@ recipes-graphics/xorg-font/font-alias_1.0.3.bb:PR = "${INC_PR}.3"
                     However, if you have very large systems that employ
                     multiple physical CPUs, you might want to make sure the
                     <filename>PARALLEL_MAKE</filename> variable is not
-                    set higher than "20".
+                    set higher than "-j 20".
                 </para>
 
                 <para>
@@ -8564,9 +8569,15 @@ recipes-graphics/xorg-font/font-alias_1.0.3.bb:PR = "${INC_PR}.3"
                     This variable defaults to the value of
                     <link linkend='var-PARALLEL_MAKE'><filename>PARALLEL_MAKE</filename></link>.
                     <note>
-                        Individual recipes might clear out this variable if
-                        the software being built has problems running its
-                        <filename>make install</filename> process in parallel.
+                        If the software being built experiences dependency
+                        issues during the
+                        <filename>do_install</filename> task that result in
+                        race conditions, you can clear the
+                        <filename>PARALLEL_MAKEINST</filename> variable within
+                        the recipe as a workaround.
+                        For information on addressing race conditions, see the
+                        "<ulink url='&YOCTO_DOCS_DEV_URL;#debugging-parallel-make-races'>Debugging Parallel Make Races</ulink>"
+                        section in the Yocto Project Development Manual.
                     </note>
                 </para>
             </glossdef>