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Message-ID: <12420098.O9o76ZdvQC@kreacher>
Date: Mon, 25 Mar 2024 17:45:30 +0100
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Linux PM <linux-pm@...r.kernel.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Subject:
[Update][PATCH v1.1 4/5] cpufreq: intel_pstate: Get rid of unnecessary
READ_ONCE() annotations
From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Drop two redundant checks involving READ_ONCE() from notify_hwp_interrupt()
and make it check hwp_active without READ_ONCE() which is not necessary,
because that variable is only set once during the early initialization of
the driver.
In order to make that clear, annotate hwp_active with __ro_after_init.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
v1 -> v1.1:
* There are two redundant checks in notify_hwp_interrupt() that can
be dropped, so drop them both.
---
drivers/cpufreq/intel_pstate.c | 23 +++--------------------
1 file changed, 3 insertions(+), 20 deletions(-)
Index: linux-pm/drivers/cpufreq/intel_pstate.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/intel_pstate.c
+++ linux-pm/drivers/cpufreq/intel_pstate.c
@@ -292,7 +292,7 @@ struct pstate_funcs {
static struct pstate_funcs pstate_funcs __read_mostly;
-static int hwp_active __read_mostly;
+static bool hwp_active __ro_after_init;
static int hwp_mode_bdw __read_mostly;
static bool per_cpu_limits __read_mostly;
static bool hwp_boost __read_mostly;
@@ -1640,7 +1640,7 @@ void notify_hwp_interrupt(void)
unsigned long flags;
u64 value;
- if (!READ_ONCE(hwp_active) || !boot_cpu_has(X86_FEATURE_HWP_NOTIFY))
+ if (!hwp_active || !boot_cpu_has(X86_FEATURE_HWP_NOTIFY))
return;
rdmsrl_safe(MSR_HWP_STATUS, &value);
@@ -1652,23 +1652,6 @@ void notify_hwp_interrupt(void)
if (!cpumask_test_cpu(this_cpu, &hwp_intr_enable_mask))
goto ack_intr;
- /*
- * Currently we never free all_cpu_data. And we can't reach here
- * without this allocated. But for safety for future changes, added
- * check.
- */
- if (unlikely(!READ_ONCE(all_cpu_data)))
- goto ack_intr;
-
- /*
- * The free is done during cleanup, when cpufreq registry is failed.
- * We wouldn't be here if it fails on init or switch status. But for
- * future changes, added check.
- */
- cpudata = READ_ONCE(all_cpu_data[this_cpu]);
- if (unlikely(!cpudata))
- goto ack_intr;
-
schedule_delayed_work(&cpudata->hwp_notify_work, msecs_to_jiffies(10));
spin_unlock_irqrestore(&hwp_notify_lock, flags);
@@ -3464,7 +3447,7 @@ static int __init intel_pstate_init(void
* deal with it.
*/
if ((!no_hwp && boot_cpu_has(X86_FEATURE_HWP_EPP)) || hwp_forced) {
- WRITE_ONCE(hwp_active, 1);
+ hwp_active = true;
hwp_mode_bdw = id->driver_data;
intel_pstate.attr = hwp_cpufreq_attrs;
intel_cpufreq.attr = hwp_cpufreq_attrs;
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