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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Fri, 21 Feb 2020 18:57:11 +0100
Subject: [PATCH 319/354] drm/vmwgfx: Drop preempt_disable() in
vmw_fifo_ping_host()
Origin: https://git.kernel.org/cgit/linux/kernel/git/rt/linux-stable-rt.git/commit?id=a6f457134aeff747dd446a6a0187eebf19cd71db
[ Upstream commit b901491e7b9b7a676818d84e482b69be72fc142f ]
vmw_fifo_ping_host() disables preemption around a test and a register
write via vmw_write(). The write function acquires a spinlock_t typed
lock which is not allowed in a preempt_disable()ed section on
PREEMPT_RT. This has been reported in the bugzilla.
It has been explained by Thomas Hellstrom that this preempt_disable()ed
section is not required for correctness.
Remove the preempt_disable() section.
Link: https://bugzilla.kernel.org/show_bug.cgi?id=206591
Link: https://lkml.kernel.org/r/0b5e1c65d89951de993deab06d1d197b40fd67aa.camel@vmware.com
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
drivers/gpu/drm/vmwgfx/vmwgfx_fifo.c | 2 --
1 file changed, 2 deletions(-)
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_fifo.c b/drivers/gpu/drm/vmwgfx/vmwgfx_fifo.c
index d0fd147ef75f..fb5a3461bb8c 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_fifo.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_fifo.c
@@ -167,10 +167,8 @@ void vmw_fifo_ping_host(struct vmw_private *dev_priv, uint32_t reason)
{
u32 *fifo_mem = dev_priv->mmio_virt;
- preempt_disable();
if (cmpxchg(fifo_mem + SVGA_FIFO_BUSY, 0, 1) == 0)
vmw_write(dev_priv, SVGA_REG_SYNC, reason);
- preempt_enable();
}
void vmw_fifo_release(struct vmw_private *dev_priv, struct vmw_fifo_state *fifo)
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