linux-kernel - [tip: sched/core] sched/preempt: Tell about PREEMPT

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Date:   Fri, 11 Mar 2022 14:40:35 -0000
From:   "tip-bot2 for Frederic Weisbecker" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Valentin Schneider <valentin.schneider@....com>,
        Frederic Weisbecker <frederic@...nel.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: sched/core] sched/preempt: Tell about PREEMPT_DYNAMIC on kernel headers

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     a0a7e453b502cbbf7ff372f907a4e27a2ebf5445
Gitweb:        https://git.kernel.org/tip/a0a7e453b502cbbf7ff372f907a4e27a2ebf5445
Author:        Frederic Weisbecker <frederic@...nel.org>
AuthorDate:    Thu, 17 Feb 2022 12:12:40 +01:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Fri, 11 Mar 2022 15:36:35 +01:00

sched/preempt: Tell about PREEMPT_DYNAMIC on kernel headers

Displaying "PREEMPT" on kernel headers when CONFIG_PREEMPT_DYNAMIC=y
can be misleading for anybody involved in remote debugging because it
is then not guaranteed that there is an actual preemption behaviour. It
depends on default Kconfig or boot defined choices.

Therefore, tell about PREEMPT_DYNAMIC on static kernel headers and leave
the search for the actual preemption behaviour to browsing dmesg.

Reviewed-by: Valentin Schneider <valentin.schneider@....com>
Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://lkml.kernel.org/r/20220217111240.GA742892@lothringen
---
 init/Makefile       |  3 ++-
 scripts/mkcompile_h | 17 ++++++++++++-----
 2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/init/Makefile b/init/Makefile
index 06326e3..d82623d 100644
--- a/init/Makefile
+++ b/init/Makefile
@@ -31,7 +31,8 @@ quiet_cmd_compile.h = CHK     $@
       cmd_compile.h = \
 	$(CONFIG_SHELL) $(srctree)/scripts/mkcompile_h $@	\
 	"$(UTS_MACHINE)" "$(CONFIG_SMP)" "$(CONFIG_PREEMPT_BUILD)"	\
-	"$(CONFIG_PREEMPT_RT)" "$(CONFIG_CC_VERSION_TEXT)" "$(LD)"
+	"$(CONFIG_PREEMPT_DYNAMIC)" "$(CONFIG_PREEMPT_RT)" \
+	"$(CONFIG_CC_VERSION_TEXT)" "$(LD)"
 
 include/generated/compile.h: FORCE
 	$(call cmd,compile.h)
diff --git a/scripts/mkcompile_h b/scripts/mkcompile_h
index 6a2a04d..ca40a52 100755
--- a/scripts/mkcompile_h
+++ b/scripts/mkcompile_h
@@ -5,9 +5,10 @@ TARGET=$1
 ARCH=$2
 SMP=$3
 PREEMPT=$4
-PREEMPT_RT=$5
-CC_VERSION="$6"
-LD=$7
+PREEMPT_DYNAMIC=$5
+PREEMPT_RT=$6
+CC_VERSION="$7"
+LD=$8
 
 # Do not expand names
 set -f
@@ -41,8 +42,14 @@ fi
 UTS_VERSION="#$VERSION"
 CONFIG_FLAGS=""
 if [ -n "$SMP" ] ; then CONFIG_FLAGS="SMP"; fi
-if [ -n "$PREEMPT" ] ; then CONFIG_FLAGS="$CONFIG_FLAGS PREEMPT"; fi
-if [ -n "$PREEMPT_RT" ] ; then CONFIG_FLAGS="$CONFIG_FLAGS PREEMPT_RT"; fi
+
+if [ -n "$PREEMPT_RT" ] ; then
+	CONFIG_FLAGS="$CONFIG_FLAGS PREEMPT_RT"
+elif [ -n "$PREEMPT_DYNAMIC" ] ; then
+	CONFIG_FLAGS="$CONFIG_FLAGS PREEMPT_DYNAMIC"
+elif [ -n "$PREEMPT" ] ; then
+	CONFIG_FLAGS="$CONFIG_FLAGS PREEMPT"
+fi
 
 # Truncate to maximum length
 UTS_LEN=64