Dear RT folks!
I'm pleased to announce the v6.5-rc4-rt2 patch set.
Changes since v6.5-rc4-rt1:
- Don't tell a CPU to push tasks for RT balancing if there are no
tasks that can be pushed.
- Preempt the timer softirq if it is PI boosted. This is to see how it
works and to start discussion with upstream how to proceed with the
underlying issue.
- Remove a mutex in x86'microcode and ASoC's mt8186 code which were
causing "unused variable" warning during RT build.
- Update a comment in ptrace code while reposting the relevant patch.
Known issues
None
The delta patch against v6.5-rc4-rt1 is appended below and can be found here:
https://cdn.kernel.org/pub/linux/kernel/projects/rt/6.5/incr/patch-6.5-rc4-rt1-rt2.patch.xz
You can get this release via the git tree at:
https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git v6.5-rc4-rt2
The RT patch against v6.5-rc4 can be found here:
https://cdn.kernel.org/pub/linux/kernel/projects/rt/6.5/older/patch-6.5-rc4-rt2.patch.xz
The split quilt queue is available at:
https://cdn.kernel.org/pub/linux/kernel/projects/rt/6.5/older/patches-6.5-rc4-rt2.tar.xz
Sebastian
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 0ba1067f4e5f1..de49b9cd8077a 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -2276,8 +2276,7 @@ void store_cpu_caps(struct cpuinfo_x86 *curr_info)
* @prev_info: CPU capabilities stored before an update.
*
* The microcode loader calls this upon late microcode load to recheck features,
- * only when microcode has been updated. Caller holds microcode_mutex and CPU
- * hotplug lock.
+ * only when microcode has been updated. Caller holds and CPU hotplug lock.
*
* Return: None
*/
diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index 3afcf3de0dd49..2f9d35744bc41 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -54,15 +54,12 @@ LIST_HEAD(microcode_cache);
*
* All non cpu-hotplug-callback call sites use:
*
- * - microcode_mutex to synchronize with each other;
* - cpus_read_lock/unlock() to synchronize with
* the cpu-hotplug-callback call sites.
*
* We guarantee that only a single cpu is being
* updated at any particular moment of time.
*/
-static DEFINE_MUTEX(microcode_mutex);
-
struct ucode_cpu_info ucode_cpu_info[NR_CPUS];
struct cpu_info_ctx {
@@ -488,10 +485,7 @@ static ssize_t reload_store(struct device *dev,
if (tmp_ret != UCODE_NEW)
goto put;
- mutex_lock(µcode_mutex);
ret = microcode_reload_late();
- mutex_unlock(µcode_mutex);
-
put:
cpus_read_unlock();
diff --git a/include/linux/bottom_half.h b/include/linux/bottom_half.h
index fc53e0ad56d90..448bbef474564 100644
--- a/include/linux/bottom_half.h
+++ b/include/linux/bottom_half.h
@@ -35,8 +35,10 @@ static inline void local_bh_enable(void)
#ifdef CONFIG_PREEMPT_RT
extern bool local_bh_blocked(void);
+extern void softirq_preempt(void);
#else
static inline bool local_bh_blocked(void) { return false; }
+static inline void softirq_preempt(void) { }
#endif
#endif /* _LINUX_BH_H */
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 973172547c125..7b235881a0ad0 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1892,6 +1892,7 @@ static inline int dl_task_check_affinity(struct task_struct *p, const struct cpu
}
#endif
+extern bool task_is_pi_boosted(const struct task_struct *p);
extern int yield_to(struct task_struct *p, bool preempt);
extern void set_user_nice(struct task_struct *p, long nice);
extern int task_prio(const struct task_struct *p);
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 6991e1982f8d9..2276b5d882380 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -8965,6 +8965,21 @@ static inline void preempt_dynamic_init(void) { }
#endif /* #ifdef CONFIG_PREEMPT_DYNAMIC */
+/*
+ * task_is_pi_boosted - Check if task has been PI boosted.
+ * @p: Task to check.
+ *
+ * Return true if task is subject to priority inheritance.
+ */
+bool task_is_pi_boosted(const struct task_struct *p)
+{
+ int prio = p->prio;
+
+ if (!rt_prio(prio))
+ return false;
+ return prio != p->normal_prio;
+}
+
/**
* yield - yield the current processor to other threads.
*
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 00e0e50741153..338cd150973ff 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -2247,8 +2247,11 @@ static int rto_next_cpu(struct root_domain *rd)
rd->rto_cpu = cpu;
- if (cpu < nr_cpu_ids)
+ if (cpu < nr_cpu_ids) {
+ if (!has_pushable_tasks(cpu_rq(cpu)))
+ continue;
return cpu;
+ }
rd->rto_cpu = -1;
diff --git a/kernel/signal.c b/kernel/signal.c
index d41eafca39687..6c9af878bd6ed 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2334,8 +2334,12 @@ static int ptrace_stop(int exit_code, int why, unsigned long message,
* between unlock and schedule() and so improving the performance since
* the ptracer has no reason to sleep.
*
- * This optimisation is not doable on PREEMPT_RT due to the spinlock_t
- * within the preempt-disable section.
+ * On PREEMPT_RT locking tasklist_lock does not disable preemption.
+ * Therefore the task can be preempted (after
+ * do_notify_parent_cldstop()) before unlocking tasklist_lock so there
+ * is no benefit in doing this. The optimisation is harmful on
+ * PEEMPT_RT because the spinlock_t (in cgroup_enter_frozen()) must not
+ * be acquired with disabled preemption.
*/
if (!IS_ENABLED(CONFIG_PREEMPT_RT))
preempt_disable();
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 623985f188336..334232227c43c 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -247,6 +247,19 @@ void __local_bh_enable_ip(unsigned long ip, unsigned int cnt)
}
EXPORT_SYMBOL(__local_bh_enable_ip);
+void softirq_preempt(void)
+{
+ if (WARN_ON_ONCE(!preemptible()))
+ return;
+
+ if (WARN_ON_ONCE(__this_cpu_read(softirq_ctrl.cnt) != SOFTIRQ_OFFSET))
+ return;
+
+ __local_bh_enable(SOFTIRQ_OFFSET, true);
+ /* preemption point */
+ __local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET);
+}
+
/*
* Invoked from ksoftirqd_run() outside of the interrupt disabled section
* to acquire the per CPU local lock for reentrancy protection.
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 7cad6fe3c035c..b3fbe97d1e342 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -1470,9 +1470,16 @@ static inline void timer_base_unlock_expiry(struct timer_base *base)
*/
static void timer_sync_wait_running(struct timer_base *base)
{
- if (atomic_read(&base->timer_waiters)) {
+ bool need_preempt;
+
+ need_preempt = task_is_pi_boosted(current);
+ if (need_preempt || atomic_read(&base->timer_waiters)) {
raw_spin_unlock_irq(&base->lock);
spin_unlock(&base->expiry_lock);
+
+ if (need_preempt)
+ softirq_preempt();
+
spin_lock(&base->expiry_lock);
raw_spin_lock_irq(&base->lock);
}
diff --git a/localversion-rt b/localversion-rt
index 6f206be67cd28..c3054d08a1129 100644
--- a/localversion-rt
+++ b/localversion-rt
@@ -1 +1 @@
--rt1
+-rt2
diff --git a/sound/soc/mediatek/mt8186/mt8186-afe-clk.c b/sound/soc/mediatek/mt8186/mt8186-afe-clk.c
index 539e3a023bc4e..70ec101890d36 100644
--- a/sound/soc/mediatek/mt8186/mt8186-afe-clk.c
+++ b/sound/soc/mediatek/mt8186/mt8186-afe-clk.c
@@ -13,8 +13,6 @@
#include "mt8186-afe-clk.h"
#include "mt8186-audsys-clk.h"
-static DEFINE_MUTEX(mutex_request_dram);
-
static const char *aud_clks[CLK_NUM] = {
[CLK_AFE] = "aud_afe_clk",
[CLK_DAC] = "aud_dac_clk",
