linux-kernel - [PATCH] USB: xhci: drop workaround for forced irq threading

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Date:   Mon, 22 Mar 2021 12:11:40 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Mathias Nyman <mathias.nyman@...el.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Johan Hovold <johan@...nel.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Bart Van Assche <bart.vanassche@...disk.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH] USB: xhci: drop workaround for forced irq threading

Force-threaded interrupt handlers used to run with interrupts enabled,
something which could lead to deadlocks in case a threaded handler
shared a lock with code running in hard interrupt context (e.g. timer
callbacks) and did not explicitly disable interrupts.

Since commit 81e2073c175b ("genirq: Disable interrupts for force
threaded handlers") interrupt handlers always run with interrupts
disabled on non-RT so that drivers no longer need to do handle forced
threading ("threadirqs").

Drop the now obsolete workaround added by commit 63aea0dbab90 ("USB:
xhci: fix lock-inversion problem").

Cc: Alan Stern <stern@...land.harvard.edu>
Cc: Bart Van Assche <bart.vanassche@...disk.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Johan Hovold <johan@...nel.org>
---
 drivers/usb/host/xhci-ring.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index ce38076901e2..20f5ded29b3b 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -3015,12 +3015,11 @@ irqreturn_t xhci_irq(struct usb_hcd *hcd)
 	struct xhci_hcd *xhci = hcd_to_xhci(hcd);
 	union xhci_trb *event_ring_deq;
 	irqreturn_t ret = IRQ_NONE;
-	unsigned long flags;
 	u64 temp_64;
 	u32 status;
 	int event_loop = 0;
 
-	spin_lock_irqsave(&xhci->lock, flags);
+	spin_lock(&xhci->lock);
 	/* Check if the xHC generated the interrupt, or the irq is shared */
 	status = readl(&xhci->op_regs->status);
 	if (status == ~(u32)0) {
@@ -3083,7 +3082,7 @@ irqreturn_t xhci_irq(struct usb_hcd *hcd)
 	ret = IRQ_HANDLED;
 
 out:
-	spin_unlock_irqrestore(&xhci->lock, flags);
+	spin_unlock(&xhci->lock);
 
 	return ret;
 }
-- 
2.26.3