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Message-Id: <20221219151503.385816-2-krzysztof.kozlowski@linaro.org>
Date: Mon, 19 Dec 2022 16:14:59 +0100
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: "Rafael J. Wysocki" <rafael@...nel.org>,
Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Kevin Hilman <khilman@...nel.org>,
Ulf Hansson <ulf.hansson@...aro.org>,
Daniel Lezcano <daniel.lezcano@...aro.org>,
Lorenzo Pieralisi <lpieralisi@...nel.org>,
Sudeep Holla <sudeep.holla@....com>, linux-pm@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
Adrien Thierry <athierry@...hat.com>,
Brian Masney <bmasney@...hat.com>,
linux-rt-users@...r.kernel.org
Subject: [PATCH v2 1/5] PM: domains: Add GENPD_FLAG_RT_SAFE for PREEMPT_RT
Realtime kernels with PREEMPT_RT must use raw_spinlock_t for domains
which are invoked from CPU idle (thus from atomic section). Example is
cpuidle PSCI domain driver which itself is PREEMPT_RT safe, but is being
called as part of cpuidle.
Add a flag allowing a power domain provider to indicate it is RT safe.
The flag is supposed to be used with existing GENPD_FLAG_IRQ_SAFE.
Cc: Adrien Thierry <athierry@...hat.com>
Cc: Brian Masney <bmasney@...hat.com>
Cc: linux-rt-users@...r.kernel.org
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
---
Independently from Adrien, I encountered the same problem around genpd
when using PREEMPT_RT kernel.
Previous patch by Adrien:
https://lore.kernel.org/all/20220615203605.1068453-1-athierry@redhat.com/
---
drivers/base/power/domain.c | 59 +++++++++++++++++++++++++++++++++++--
include/linux/pm_domain.h | 13 ++++++++
2 files changed, 70 insertions(+), 2 deletions(-)
diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 967bcf9d415e..4dfce1d476f4 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -119,6 +119,48 @@ static const struct genpd_lock_ops genpd_spin_ops = {
.unlock = genpd_unlock_spin,
};
+static void genpd_lock_rawspin(struct generic_pm_domain *genpd)
+ __acquires(&genpd->rslock)
+{
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&genpd->rslock, flags);
+ genpd->rlock_flags = flags;
+}
+
+static void genpd_lock_nested_rawspin(struct generic_pm_domain *genpd,
+ int depth)
+ __acquires(&genpd->rslock)
+{
+ unsigned long flags;
+
+ raw_spin_lock_irqsave_nested(&genpd->rslock, flags, depth);
+ genpd->rlock_flags = flags;
+}
+
+static int genpd_lock_interruptible_rawspin(struct generic_pm_domain *genpd)
+ __acquires(&genpd->rslock)
+{
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&genpd->rslock, flags);
+ genpd->rlock_flags = flags;
+ return 0;
+}
+
+static void genpd_unlock_rawspin(struct generic_pm_domain *genpd)
+ __releases(&genpd->rslock)
+{
+ raw_spin_unlock_irqrestore(&genpd->rslock, genpd->rlock_flags);
+}
+
+static const struct genpd_lock_ops genpd_rawspin_ops = {
+ .lock = genpd_lock_rawspin,
+ .lock_nested = genpd_lock_nested_rawspin,
+ .lock_interruptible = genpd_lock_interruptible_rawspin,
+ .unlock = genpd_unlock_rawspin,
+};
+
#define genpd_lock(p) p->lock_ops->lock(p)
#define genpd_lock_nested(p, d) p->lock_ops->lock_nested(p, d)
#define genpd_lock_interruptible(p) p->lock_ops->lock_interruptible(p)
@@ -126,6 +168,8 @@ static const struct genpd_lock_ops genpd_spin_ops = {
#define genpd_status_on(genpd) (genpd->status == GENPD_STATE_ON)
#define genpd_is_irq_safe(genpd) (genpd->flags & GENPD_FLAG_IRQ_SAFE)
+#define genpd_is_rt_safe(genpd) (genpd_is_irq_safe(genpd) && \
+ (genpd->flags & GENPD_FLAG_RT_SAFE))
#define genpd_is_always_on(genpd) (genpd->flags & GENPD_FLAG_ALWAYS_ON)
#define genpd_is_active_wakeup(genpd) (genpd->flags & GENPD_FLAG_ACTIVE_WAKEUP)
#define genpd_is_cpu_domain(genpd) (genpd->flags & GENPD_FLAG_CPU_DOMAIN)
@@ -1838,6 +1882,12 @@ static int genpd_add_subdomain(struct generic_pm_domain *genpd,
return -EINVAL;
}
+ if (!genpd_is_rt_safe(genpd) && genpd_is_rt_safe(subdomain)) {
+ WARN(1, "Parent %s of subdomain %s must be RT safe\n",
+ genpd->name, subdomain->name);
+ return -EINVAL;
+ }
+
link = kzalloc(sizeof(*link), GFP_KERNEL);
if (!link)
return -ENOMEM;
@@ -2008,8 +2058,13 @@ static void genpd_free_data(struct generic_pm_domain *genpd)
static void genpd_lock_init(struct generic_pm_domain *genpd)
{
if (genpd->flags & GENPD_FLAG_IRQ_SAFE) {
- spin_lock_init(&genpd->slock);
- genpd->lock_ops = &genpd_spin_ops;
+ if (genpd->flags & GENPD_FLAG_RT_SAFE) {
+ raw_spin_lock_init(&genpd->rslock);
+ genpd->lock_ops = &genpd_rawspin_ops;
+ } else {
+ spin_lock_init(&genpd->slock);
+ genpd->lock_ops = &genpd_spin_ops;
+ }
} else {
mutex_init(&genpd->mlock);
genpd->lock_ops = &genpd_mtx_ops;
diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
index 1cd41bdf73cf..0a1600244963 100644
--- a/include/linux/pm_domain.h
+++ b/include/linux/pm_domain.h
@@ -61,6 +61,14 @@
* GENPD_FLAG_MIN_RESIDENCY: Enable the genpd governor to consider its
* components' next wakeup when determining the
* optimal idle state.
+ *
+ * GENPD_FLAG_RT_SAFE: When used with GENPD_FLAG_IRQ_SAFE, this informs
+ * genpd that its backend callbacks, ->power_on|off(),
+ * do not use other spinlocks. They might use
+ * raw_spinlocks or other pre-emption-disable
+ * methods, all of which are PREEMPT_RT safe. Note
+ * that, a genpd having this flag set, requires its
+ * masterdomains to also have it set.
*/
#define GENPD_FLAG_PM_CLK (1U << 0)
#define GENPD_FLAG_IRQ_SAFE (1U << 1)
@@ -69,6 +77,7 @@
#define GENPD_FLAG_CPU_DOMAIN (1U << 4)
#define GENPD_FLAG_RPM_ALWAYS_ON (1U << 5)
#define GENPD_FLAG_MIN_RESIDENCY (1U << 6)
+#define GENPD_FLAG_RT_SAFE (1U << 7)
enum gpd_status {
GENPD_STATE_ON = 0, /* PM domain is on */
@@ -164,6 +173,10 @@ struct generic_pm_domain {
spinlock_t slock;
unsigned long lock_flags;
};
+ struct {
+ raw_spinlock_t rslock;
+ unsigned long rlock_flags;
+ };
};
};
--
2.34.1
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