| Message ID | 20200224140726.1550689-1-bigeasy@linutronix.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [1/2] drm/vmwgfx: Drop preempt_disable() in vmw_fifo_ping_host() | expand |
On Mon, 2020-02-24 at 15:07 +0100, Sebastian Andrzej Siewior wrote: > 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. > Hi, Sebastian, I suppose there isn't something like a preempt_disable_unless_RT() macro? If not, Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com> I'll include in the next vmwgfx-next pull request Thanks, Thomas
On 2020-02-26 15:01:15 [+0000], Thomas Hellstrom wrote: > Hi, Sebastian, Hi Thomas, > I suppose there isn't something like a preempt_disable_unless_RT() > macro? We got rid of most users of "preempt_disable_unless_RT()" since it was used as a duct tape. We still have it in the rt-devel tree but we have a plan for most users and we don't intend to get it upstream. > If not, > Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com> > > I'll include in the next vmwgfx-next pull request Thank you. > Thanks, > Thomas Sebastian
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_fifo.c b/drivers/gpu/drm/vmwgfx/vmwgfx_fifo.c index e5252ef3812f0..6941689085ed3 100644 --- a/drivers/gpu/drm/vmwgfx/vmwgfx_fifo.c +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_fifo.c @@ -169,10 +169,8 @@ 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)
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> --- drivers/gpu/drm/vmwgfx/vmwgfx_fifo.c | 2 -- 1 file changed, 2 deletions(-)