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From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Thomas Gleixner <tglx@linutronix.de>,
	alsa-devel@alsa-project.org, Takashi Iwai <tiwai@suse.com>,
	Jaroslav Kysela <perex@perex.cz>, Takashi Iwai <tiwai@suse.de>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH MANUALSEL 5.14 9/9] ALSA: pcsp: Make hrtimer forwarding more robust
Date: Wed,  6 Oct 2021 09:30:21 -0400	[thread overview]
Message-ID: <20211006133021.271905-9-sashal@kernel.org> (raw)
In-Reply-To: <20211006133021.271905-1-sashal@kernel.org>

From: Thomas Gleixner <tglx@linutronix.de>

[ Upstream commit f2ff7147c6834f244b8ce636b12e71a3bd044629 ]

The hrtimer callback pcsp_do_timer() prepares rearming of the timer with
hrtimer_forward(). hrtimer_forward() is intended to provide a mechanism to
forward the expiry time of the hrtimer by a multiple of the period argument
so that the expiry time greater than the time provided in the 'now'
argument.

pcsp_do_timer() invokes hrtimer_forward() with the current timer expiry
time as 'now' argument. That's providing a periodic timer expiry, but is
not really robust when the timer callback is delayed so that the resulting
new expiry time is already in the past which causes the callback to be
invoked immediately again. If the timer is delayed then the back to back
invocation is not really making it better than skipping the missed
periods. Sound is distorted in any case.

Use hrtimer_forward_now() which ensures that the next expiry is in the
future. This prevents hogging the CPU in the timer expiry code and allows
later on to remove hrtimer_forward() from the public interfaces.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: alsa-devel@alsa-project.org
Cc: Takashi Iwai <tiwai@suse.com>
Cc: Jaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/20210923153339.623208460@linutronix.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 sound/drivers/pcsp/pcsp_lib.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sound/drivers/pcsp/pcsp_lib.c b/sound/drivers/pcsp/pcsp_lib.c
index ed40d0f7432c..773db4bf0876 100644
--- a/sound/drivers/pcsp/pcsp_lib.c
+++ b/sound/drivers/pcsp/pcsp_lib.c
@@ -143,7 +143,7 @@ enum hrtimer_restart pcsp_do_timer(struct hrtimer *handle)
 	if (pointer_update)
 		pcsp_pointer_update(chip);
 
-	hrtimer_forward(handle, hrtimer_get_expires(handle), ns_to_ktime(ns));
+	hrtimer_forward_now(handle, ns_to_ktime(ns));
 
 	return HRTIMER_RESTART;
 }
-- 
2.33.0


  parent reply	other threads:[~2021-10-06 13:30 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-06 13:30 [PATCH MANUALSEL 5.14 1/9] selftests: KVM: Align SMCCC call with the spec in steal_time Sasha Levin
2021-10-06 13:30 ` [PATCH MANUALSEL 5.14 2/9] KVM: x86: Handle SRCU initialization failure during page track init Sasha Levin
2021-10-06 13:36   ` Paolo Bonzini
2021-10-06 13:30 ` [PATCH MANUALSEL 5.14 3/9] KVM: do not shrink halt_poll_ns below grow_start Sasha Levin
2021-10-06 13:36   ` Paolo Bonzini
2021-10-06 13:30 ` [PATCH MANUALSEL 5.14 4/9] KVM: x86: reset pdptrs_from_userspace when exiting smm Sasha Levin
2021-10-06 13:36   ` Paolo Bonzini
2021-10-07 15:23     ` Naresh Kamboju
2021-10-07 17:47       ` Paolo Bonzini
2021-10-06 13:30 ` [PATCH MANUALSEL 5.14 5/9] KVM: x86: VMX: synthesize invalid VM exit when emulating invalid guest state Sasha Levin
2021-10-06 13:35   ` Paolo Bonzini
2021-10-06 13:30 ` [PATCH MANUALSEL 5.14 6/9] KVM: x86: nVMX: don't fail nested VM entry on invalid guest state if !from_vmentry Sasha Levin
2021-10-06 13:36   ` Paolo Bonzini
2021-10-06 13:30 ` [PATCH MANUALSEL 5.14 7/9] kvm: x86: Add AMD PMU MSRs to msrs_to_save_all[] Sasha Levin
2021-10-06 13:36   ` Paolo Bonzini
2021-10-06 13:30 ` [PATCH MANUALSEL 5.14 8/9] KVM: x86: nSVM: restore int_vector in svm_clear_vintr Sasha Levin
2021-10-06 13:36   ` Paolo Bonzini
2021-10-06 13:30 ` Sasha Levin [this message]
2021-10-06 13:36 ` [PATCH MANUALSEL 5.14 1/9] selftests: KVM: Align SMCCC call with the spec in steal_time Paolo Bonzini

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