From: zanussi@kernel.org
To: LKML <linux-kernel@vger.kernel.org>,
linux-rt-users <linux-rt-users@vger.kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Thomas Gleixner <tglx@linutronix.de>,
Carsten Emde <C.Emde@osadl.org>, John Kacur <jkacur@redhat.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Daniel Wagner <wagi@monom.org>, Tom Zanussi <zanussi@kernel.org>
Subject: [PATCH RT 6/8] drm/vmwgfx: Drop preempt_disable() in vmw_fifo_ping_host()
Date: Mon, 9 Mar 2020 14:47:51 -0500 [thread overview]
Message-ID: <7b50a4187b38dd305b91907c235c2382cc87bca1.1583783251.git.zanussi@kernel.org> (raw)
In-Reply-To: <cover.1583783251.git.zanussi@kernel.org>
In-Reply-To: <cover.1583783251.git.zanussi@kernel.org>
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
v4.14.172-rt78-rc1 stable review patch.
If anyone has any objections, please let me know.
-----------
[ 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: Tom Zanussi <zanussi@kernel.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 a1c68e6a689e3..713f202fca2cd 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)
--
2.14.1
next prev parent reply other threads:[~2020-03-09 19:48 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-09 19:47 [PATCH RT 0/8] Linux v4.14.172-rt78-rc1 zanussi
2020-03-09 19:47 ` [PATCH RT 1/8] userfaultfd: Use a seqlock instead of seqcount zanussi
2020-03-09 19:47 ` [PATCH RT 2/8] sched: migrate_enable: Use per-cpu cpu_stop_work zanussi
2020-03-09 19:47 ` [PATCH RT 3/8] sched: migrate_enable: Remove __schedule() call zanussi
2020-03-09 19:47 ` [PATCH RT 4/8] mm/memcontrol: Move misplaced local_unlock_irqrestore() zanussi
2020-03-09 19:47 ` [PATCH RT 5/8] locallock: Include header for the `current' macro zanussi
2020-03-09 19:47 ` zanussi [this message]
2020-03-09 19:47 ` [PATCH RT 7/8] tracing: make preempt_lazy and migrate_disable counter smaller zanussi
2020-03-09 19:47 ` [PATCH RT 8/8] Linux 4.14.172-rt78-rc1 zanussi
-- strict thread matches above, loose matches on Subject: below --
2020-03-06 18:40 [PATCH RT 0/8] Linux 4.19.106-rt45-rc1 Steven Rostedt
2020-03-06 18:40 ` [PATCH RT 6/8] drm/vmwgfx: Drop preempt_disable() in vmw_fifo_ping_host() Steven Rostedt
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