bitbake.conf: Limit the number of OpenMP threads

Limits the number of OpenMP threads to match BB_NUMBER_THREADS. This
prevents OpenMP (libgomp in particular) from falling back to using all
the available CPUs, which behaves poorly when attempting to limit build
usage, especially when attempting to build in a container.

(From OE-Core rev: fd2b8986aef11609123da917aaf6bcbe41f63112)

Signed-off-by: Joshua Watt <JPEWhacker@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 6 insertions, 1 deletions

diff --git a/meta/conf/bitbake.conf b/meta/conf/bitbake.conf
index d87d7cafb6..385fc7dd55 100644
--- a/meta/conf/bitbake.conf
+++ b/meta/conf/bitbake.conf
@@ -810,6 +810,10 @@ XZ_THREADS ?= "${@oe.utils.cpu_count(at_least=2)}"
 XZ_DEFAULTS ?= "--memlimit=${XZ_MEMLIMIT} --threads=${XZ_THREADS}"
 XZ_DEFAULTS[vardepsexclude] += "XZ_MEMLIMIT XZ_THREADS"
 
+# Limit the number of threads that OpenMP libraries will use. Otherwise they
+# may fallback to using all CPUs
+export OMP_NUM_THREADS = "${BB_NUMBER_THREADS}"
+
 ##################################################################
 # Magic Cookie for SANITY CHECK
 ##################################################################
@@ -891,7 +895,8 @@ BB_HASHEXCLUDE_COMMON ?= "TMPDIR FILE PATH PWD BB_TASKHASH BBPATH BBSERVER DL_DI
     WARN_QA ERROR_QA WORKDIR STAMPCLEAN PKGDATA_DIR BUILD_ARCH SSTATE_PKGARCH \
     BB_WORKERCONTEXT BB_LIMITEDDEPS BB_UNIHASH extend_recipe_sysroot DEPLOY_DIR \
     SSTATE_HASHEQUIV_METHOD SSTATE_HASHEQUIV_REPORT_TASKDATA \
-    SSTATE_HASHEQUIV_OWNER CCACHE_TOP_DIR BB_HASHSERVE GIT_CEILING_DIRECTORIES"
+    SSTATE_HASHEQUIV_OWNER CCACHE_TOP_DIR BB_HASHSERVE GIT_CEILING_DIRECTORIES \
+    OMP_NUM_THREADS"
 BB_HASHBASE_WHITELIST ?= "${BB_HASHEXCLUDE_COMMON} PSEUDO_IGNORE_PATHS BUILDHISTORY_DIR SSTATE_DIR "
 BB_HASHCONFIG_WHITELIST ?= "${BB_HASHEXCLUDE_COMMON} DATE TIME SSH_AGENT_PID \
     SSH_AUTH_SOCK PSEUDO_BUILD BB_ENV_EXTRAWHITE DISABLE_SANITY_CHECKS \