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PM / QoS: add lockless read for flags

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Add a lockless read for QoS flags similar to the lockless read for
resume latency (dev_pm_qos_raw_resume_latency) which may be called
from atomic context (e.g. genpd governors running under a raw spinlock
or in the syscore suspend path), where taking that sleeping lock would
be invalid on PREEMPT_RT.

dev_pm_qos_raw_flags() now reads dev->power.qos->flags.effective_flags
with READ_ONCE() so also add corresponding WRITE_ONCE() to the two
effective_flags writes, the same way pm_qos_set_value() already does
for target_value/pm_qos_read_value().

Reviewed-by: Kendall Willis <k-willis@ti.com>
Acked-by: Rafael J. Wysocki (Intel) <rafael@kernel.org>
Signed-off-by: Kevin Hilman (TI) <khilman@baylibre.com>
Signed-off-by: Ulf Hansson <ulfh@kernel.org>
This commit is contained in:
Kevin Hilman (TI) 2026-09-24 13:29:57 -07:00 committed by Ulf Hansson
parent 4ff08254de
commit b7cbbc33bc
2 changed files with 9 additions and 2 deletions
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7
include/linux/pm_qos.h
View File

@ -219,6 +219,12 @@ static inline s32 dev_pm_qos_raw_resume_latency(struct device *dev)
PM_QOS_RESUME_LATENCY_NO_CONSTRAINT :
pm_qos_read_value(&dev->power.qos->resume_latency);
}
static inline s32 dev_pm_qos_raw_flags(struct device *dev)
{
return IS_ERR_OR_NULL(dev->power.qos) ?
0 : READ_ONCE(dev->power.qos->flags.effective_flags);
}
#else
static inline enum pm_qos_flags_status __dev_pm_qos_flags(struct device *dev,
s32 mask)
@ -300,6 +306,7 @@ static inline s32 dev_pm_qos_raw_resume_latency(struct device *dev)
{
return PM_QOS_RESUME_LATENCY_NO_CONSTRAINT;
}
static inline s32 dev_pm_qos_raw_flags(struct device *dev) { return 0; }
#endif
static inline int freq_qos_request_active(struct freq_qos_request *req)

4
kernel/power/qos.c
View File

@ -159,7 +159,7 @@ static void pm_qos_flags_remove_req(struct pm_qos_flags *pqf,
list_for_each_entry(req, &pqf->list, node)
val |= req->flags;
pqf->effective_flags = val;
WRITE_ONCE(pqf->effective_flags, val);
}
/**
@ -193,7 +193,7 @@ bool pm_qos_update_flags(struct pm_qos_flags *pqf,
req->flags = val;
INIT_LIST_HEAD(&req->node);
list_add_tail(&req->node, &pqf->list);
pqf->effective_flags |= val;
WRITE_ONCE(pqf->effective_flags, pqf->effective_flags | val);
break;
default:
/* no action */