netdev - [patch V3 12/20] powerpc/ps3: Convert half completion to rcuwait

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Message-Id: <20200321113241.930037873@linutronix.de>
Date:   Sat, 21 Mar 2020 12:25:56 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Sebastian Siewior <bigeasy@...utronix.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Michael Ellerman <mpe@...erman.id.au>,
        Arnd Bergmann <arnd@...db.de>,
        Geoff Levand <geoff@...radead.org>,
        linuxppc-dev@...ts.ozlabs.org,
        Logan Gunthorpe <logang@...tatee.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Kurt Schwemmer <kurt.schwemmer@...rosemi.com>,
        linux-pci@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Felipe Balbi <balbi@...nel.org>, linux-usb@...r.kernel.org,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        platform-driver-x86@...r.kernel.org,
        Zhang Rui <rui.zhang@...el.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        linux-pm@...r.kernel.org, Len Brown <lenb@...nel.org>,
        linux-acpi@...r.kernel.org, kbuild test robot <lkp@...el.com>,
        Nick Hu <nickhu@...estech.com>,
        Greentime Hu <green.hu@...il.com>,
        Vincent Chen <deanbo422@...il.com>,
        Guo Ren <guoren@...nel.org>, linux-csky@...r.kernel.org,
        Brian Cain <bcain@...eaurora.org>,
        linux-hexagon@...r.kernel.org, Tony Luck <tony.luck@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>, linux-ia64@...r.kernel.org,
        Michal Simek <monstr@...str.eu>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Jonathan Corbet <corbet@....net>,
        Randy Dunlap <rdunlap@...radead.org>,
        Davidlohr Bueso <dbueso@...e.de>
Subject: [patch V3 12/20] powerpc/ps3: Convert half completion to rcuwait

From: Thomas Gleixner <tglx@...utronix.de>

The PS3 notification interrupt and kthread use a hacked up completion to
communicate. Since we're wanting to change the completion implementation and
this is abuse anyway, replace it with a simple rcuwait since there is only ever
the one waiter.

AFAICT the kthread uses TASK_INTERRUPTIBLE to not increase loadavg, kthreads
cannot receive signals by default and this one doesn't look different. Use
TASK_IDLE instead.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Michael Ellerman <mpe@...erman.id.au>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: Geoff Levand <geoff@...radead.org>
Cc: linuxppc-dev@...ts.ozlabs.org
---
V3: Folded the init fix from bigeasy
V2: New patch to avoid the magic completion wait variant
---
 arch/powerpc/platforms/ps3/device-init.c |   18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

--- a/arch/powerpc/platforms/ps3/device-init.c
+++ b/arch/powerpc/platforms/ps3/device-init.c
@@ -13,6 +13,7 @@
 #include <linux/init.h>
 #include <linux/slab.h>
 #include <linux/reboot.h>
+#include <linux/rcuwait.h>
 
 #include <asm/firmware.h>
 #include <asm/lv1call.h>
@@ -670,7 +671,8 @@ struct ps3_notification_device {
 	spinlock_t lock;
 	u64 tag;
 	u64 lv1_status;
-	struct completion done;
+	struct rcuwait wait;
+	bool done;
 };
 
 enum ps3_notify_type {
@@ -712,7 +714,8 @@ static irqreturn_t ps3_notification_inte
 		pr_debug("%s:%u: completed, status 0x%llx\n", __func__,
 			 __LINE__, status);
 		dev->lv1_status = status;
-		complete(&dev->done);
+		dev->done = true;
+		rcuwait_wake_up(&dev->wait);
 	}
 	spin_unlock(&dev->lock);
 	return IRQ_HANDLED;
@@ -725,12 +728,12 @@ static int ps3_notification_read_write(s
 	unsigned long flags;
 	int res;
 
-	init_completion(&dev->done);
 	spin_lock_irqsave(&dev->lock, flags);
 	res = write ? lv1_storage_write(dev->sbd.dev_id, 0, 0, 1, 0, lpar,
 					&dev->tag)
 		    : lv1_storage_read(dev->sbd.dev_id, 0, 0, 1, 0, lpar,
 				       &dev->tag);
+	dev->done = false;
 	spin_unlock_irqrestore(&dev->lock, flags);
 	if (res) {
 		pr_err("%s:%u: %s failed %d\n", __func__, __LINE__, op, res);
@@ -738,14 +741,10 @@ static int ps3_notification_read_write(s
 	}
 	pr_debug("%s:%u: notification %s issued\n", __func__, __LINE__, op);
 
-	res = wait_event_interruptible(dev->done.wait,
-				       dev->done.done || kthread_should_stop());
+	rcuwait_wait_event(&dev->wait, dev->done || kthread_should_stop(), TASK_IDLE);
+
 	if (kthread_should_stop())
 		res = -EINTR;
-	if (res) {
-		pr_debug("%s:%u: interrupted %s\n", __func__, __LINE__, op);
-		return res;
-	}
 
 	if (dev->lv1_status) {
 		pr_err("%s:%u: %s not completed, status 0x%llx\n", __func__,
@@ -810,6 +809,7 @@ static int ps3_probe_thread(void *data)
 	}
 
 	spin_lock_init(&dev.lock);
+	rcuwait_init(&dev.wait);
 
 	res = request_irq(irq, ps3_notification_interrupt, 0,
 			  "ps3_notification", &dev);