linux-kernel - [tip: locking/urgent] intel_idle: Fix intel

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Date:   Wed, 25 Nov 2020 13:57:07 -0000
From:   "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: locking/urgent] intel_idle: Fix intel_idle() vs tracing

The following commit has been merged into the locking/urgent branch of tip:

Commit-ID:     6e1d2bc675bd57640f5658a4a657ae488db4c204
Gitweb:        https://git.kernel.org/tip/6e1d2bc675bd57640f5658a4a657ae488db4c204
Author:        Peter Zijlstra <peterz@...radead.org>
AuthorDate:    Fri, 20 Nov 2020 11:28:35 +01:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Tue, 24 Nov 2020 16:47:36 +01:00

intel_idle: Fix intel_idle() vs tracing

cpuidle->enter() callbacks should not call into tracing because RCU
has already been disabled. Instead of doing the broadcast thing
itself, simply advertise to the cpuidle core that those states stop
the timer.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Link: https://lkml.kernel.org/r/20201123143510.GR3021@hirez.programming.kicks-ass.net
---
 drivers/idle/intel_idle.c | 37 ++++++++++++++++++++-----------------
 1 file changed, 20 insertions(+), 17 deletions(-)

diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index 01bace4..7ee7ffe 100644
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -126,26 +126,9 @@ static __cpuidle int intel_idle(struct cpuidle_device *dev,
 	struct cpuidle_state *state = &drv->states[index];
 	unsigned long eax = flg2MWAIT(state->flags);
 	unsigned long ecx = 1; /* break on interrupt flag */
-	bool tick;
-
-	if (!static_cpu_has(X86_FEATURE_ARAT)) {
-		/*
-		 * Switch over to one-shot tick broadcast if the target C-state
-		 * is deeper than C1.
-		 */
-		if ((eax >> MWAIT_SUBSTATE_SIZE) & MWAIT_CSTATE_MASK) {
-			tick = true;
-			tick_broadcast_enter();
-		} else {
-			tick = false;
-		}
-	}
 
 	mwait_idle_with_hints(eax, ecx);
 
-	if (!static_cpu_has(X86_FEATURE_ARAT) && tick)
-		tick_broadcast_exit();
-
 	return index;
 }
 
@@ -1227,6 +1210,20 @@ static bool __init intel_idle_acpi_cst_extract(void)
 	return false;
 }
 
+static bool __init intel_idle_state_needs_timer_stop(struct cpuidle_state *state)
+{
+	unsigned long eax = flg2MWAIT(state->flags);
+
+	if (boot_cpu_has(X86_FEATURE_ARAT))
+		return false;
+
+	/*
+	 * Switch over to one-shot tick broadcast if the target C-state
+	 * is deeper than C1.
+	 */
+	return !!((eax >> MWAIT_SUBSTATE_SIZE) & MWAIT_CSTATE_MASK);
+}
+
 static void __init intel_idle_init_cstates_acpi(struct cpuidle_driver *drv)
 {
 	int cstate, limit = min_t(int, CPUIDLE_STATE_MAX, acpi_state_table.count);
@@ -1269,6 +1266,9 @@ static void __init intel_idle_init_cstates_acpi(struct cpuidle_driver *drv)
 		if (disabled_states_mask & BIT(cstate))
 			state->flags |= CPUIDLE_FLAG_OFF;
 
+		if (intel_idle_state_needs_timer_stop(state))
+			state->flags |= CPUIDLE_FLAG_TIMER_STOP;
+
 		state->enter = intel_idle;
 		state->enter_s2idle = intel_idle_s2idle;
 	}
@@ -1507,6 +1507,9 @@ static void __init intel_idle_init_cstates_icpu(struct cpuidle_driver *drv)
 		     !(cpuidle_state_table[cstate].flags & CPUIDLE_FLAG_ALWAYS_ENABLE)))
 			drv->states[drv->state_count].flags |= CPUIDLE_FLAG_OFF;
 
+		if (intel_idle_state_needs_timer_stop(&drv->states[drv->state_count]))
+			drv->states[drv->state_count].flags |= CPUIDLE_FLAG_TIMER_STOP;
+
 		drv->state_count++;
 	}