[ANNOUNCE] v5.3.18-rt13v5.3.18-rt13-patchesv5.3-rt-patches

    Changes since v5.3.18-rt12:

          - Since the migrate_disable() rework, the kernel did not build on UP
            or without RT enabled. Patch by Daniel Wagner.

          - Since the migrate_disable() rework, with heave changing of the
            task's affinity mask the kernel could issue a warning in
            migrate_enable() and crash later.

Known issues
   - none

You can get this release via the git tree at:

   git://git.kernel.org/pub/scm/linux/kernel/git/wagi/linux-stable-rt.git v5.3.18-rt13

Daniel

Signed-off-by: Daniel Wagner <dwagner@suse.de>

5 files changed, 83 insertions, 6 deletions

diff --git a/patches/lib-smp_processor_id-Adjust-check_preemption_disable.patch b/patches/lib-smp_processor_id-Adjust-check_preemption_disable.patch
new file mode 100644
index 00000000000000..c9c57619a90fd6
--- /dev/null
+++ b/patches/lib-smp_processor_id-Adjust-check_preemption_disable.patch
@@ -0,0 +1,30 @@
+From: Daniel Wagner <dwagner@suse.de>
+Date: Mon, 16 Dec 2019 16:15:57 +0100
+Subject: [PATCH] lib/smp_processor_id: Adjust check_preemption_disabled()
+
+The current->migrate_disable counter is not always defined leading to
+build failures with DEBUG_PREEMPT && !PREEMPT_RT_BASE.
+
+Restrict the access to ->migrate_disable to same set where
+->migrate_disable is modified.
+
+Signed-off-by: Daniel Wagner <dwagner@suse.de>
+[bigeasy: adjust condition + description]
+Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+---
+ lib/smp_processor_id.c |    2 ++
+ 1 file changed, 2 insertions(+)
+
+--- a/lib/smp_processor_id.c
++++ b/lib/smp_processor_id.c
+@@ -23,8 +23,10 @@ unsigned int check_preemption_disabled(c
+ 	 * Kernel threads bound to a single CPU can safely use
+ 	 * smp_processor_id():
+ 	 */
++#if defined(CONFIG_PREEMPT_RT_BASE) && (defined(CONFIG_SMP) || defined(CONFIG_SCHED_DEBUG))
+ 	if (current->migrate_disable)
+ 		goto out;
++#endif
+ 
+ 	if (current->nr_cpus_allowed == 1)
+ 		goto out;
diff --git a/patches/localversion.patch b/patches/localversion.patch
index 507b529ef21276..9b4c46bf93b1a4 100644
--- a/patches/localversion.patch
+++ b/patches/localversion.patch
@@ -10,4 +10,4 @@ Signed-off-by: Daniel Wagner <dwagern@suse.de>
 --- /dev/null
 +++ b/localversion-rt
 @@ -0,0 +1 @@
-+-rt12
++-rt13
diff --git a/patches/sched-Lazy-migrate_disable-processing.patch b/patches/sched-Lazy-migrate_disable-processing.patch
index 0cc5d0f6681af4..052f0ded3cfbd6 100644
--- a/patches/sched-Lazy-migrate_disable-processing.patch
+++ b/patches/sched-Lazy-migrate_disable-processing.patch
@@ -36,8 +36,8 @@ Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
  kernel/cpu.c           |  103 ++++++++++------------------
  kernel/sched/core.c    |  180 +++++++++++++++++++------------------------------
  kernel/sched/sched.h   |    4 +
- lib/smp_processor_id.c |    5 +
- 7 files changed, 130 insertions(+), 181 deletions(-)
+ lib/smp_processor_id.c |    3 
+ 7 files changed, 128 insertions(+), 181 deletions(-)
 
 --- a/include/linux/cpu.h
 +++ b/include/linux/cpu.h
@@ -579,14 +579,12 @@ Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
  #ifdef CONFIG_FAIR_GROUP_SCHED
 --- a/lib/smp_processor_id.c
 +++ b/lib/smp_processor_id.c
-@@ -23,6 +23,11 @@ unsigned int check_preemption_disabled(c
+@@ -23,6 +23,9 @@ unsigned int check_preemption_disabled(c
  	 * Kernel threads bound to a single CPU can safely use
  	 * smp_processor_id():
  	 */
-+#if defined(CONFIG_SMP) && defined(CONFIG_PREEMPT_RT_BASE)
 +	if (current->migrate_disable)
 +		goto out;
-+#endif
 +
  	if (current->nr_cpus_allowed == 1)
  		goto out;
diff --git a/patches/sched-migrate_enable-Busy-loop-until-the-migration-r.patch b/patches/sched-migrate_enable-Busy-loop-until-the-migration-r.patch
new file mode 100644
index 00000000000000..623cfb9a953718
--- /dev/null
+++ b/patches/sched-migrate_enable-Busy-loop-until-the-migration-r.patch
@@ -0,0 +1,47 @@
+From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+Date: Thu, 12 Dec 2019 10:53:59 +0100
+Subject: [PATCH] sched: migrate_enable: Busy loop until the migration
+ request is completed
+
+If user task changes the CPU affinity mask of a running task it will
+dispatch migration request if the current CPU is no longer allowed. This
+might happen shortly before a task enters a migrate_disable() section.
+Upon leaving the migrate_disable() section, the task will notice that
+the current CPU is no longer allowed and will will dispatch its own
+migration request to move it off the current CPU.
+While invoking __schedule() the first migration request will be
+processed and the task returns on the "new" CPU with "arg.done = 0". Its
+own migration request will be processed shortly after and will result in
+memory corruption if the stack memory, designed for request, was used
+otherwise in the meantime.
+
+Spin until the migration request has been processed if it was accepted.
+
+Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+---
+ kernel/sched/core.c |    7 +++++--
+ 1 file changed, 5 insertions(+), 2 deletions(-)
+
+--- a/kernel/sched/core.c
++++ b/kernel/sched/core.c
+@@ -7867,7 +7867,7 @@ void migrate_enable(void)
+ 
+ 	WARN_ON(smp_processor_id() != cpu);
+ 	if (!is_cpu_allowed(p, cpu)) {
+-		struct migration_arg arg = { p };
++		struct migration_arg arg = { .task = p };
+ 		struct cpu_stop_work work;
+ 		struct rq_flags rf;
+ 
+@@ -7879,7 +7879,10 @@ void migrate_enable(void)
+ 		stop_one_cpu_nowait(task_cpu(p), migration_cpu_stop,
+ 				    &arg, &work);
+ 		__schedule(true);
+-		WARN_ON_ONCE(!arg.done && !work.disabled);
++		if (!work.disabled) {
++			while (!arg.done)
++				cpu_relax();
++		}
+ 	}
+ 
+ out:
diff --git a/patches/series b/patches/series
index 76740c232fb699..7831a342a0a1c7 100644
--- a/patches/series
+++ b/patches/series
@@ -416,6 +416,8 @@ sched-migrate_enable-Use-select_fallback_rq.patch
 sched-Lazy-migrate_disable-processing.patch
 sched-migrate_enable-Use-stop_one_cpu_nowait.patch
 sched-core-migrate_enable-must-access-takedown_cpu_t.patch
+sched-migrate_enable-Busy-loop-until-the-migration-r.patch
+lib-smp_processor_id-Adjust-check_preemption_disable.patch
 
 # DRIVERS
 connector-cn_proc-Protect-send_msg-with-a-local-lock.patch