gma_power_begin() starts with locking power_ctrl_lock spinlock and then,
if gma_resume_pci(dev->pdev) succeed, it calls
psb_irq_preinstall(dev);
psb_irq_postinstall(dev);
psb_irq_postinstall() does some pipestat enabling/disabling dance:
if (dev->vblank[0].enabled)
psb_enable_pipestat(dev_priv, 0, PIPE_VBLANK_INTERRUPT_ENABLE);
else
psb_disable_pipestat(dev_priv, 0, PIPE_VBLANK_INTERRUPT_ENABLE);
where
void psb_enable_pipestat(struct drm_psb_private *dev_priv, int pipe, u32
mask)
{
if ((dev_priv->pipestat[pipe] & mask) != mask) {
u32 reg = psb_pipestat(pipe);
dev_priv->pipestat[pipe] |= mask;
/* Enable the interrupt, clear any pending status */
if (gma_power_begin(dev_priv->dev, false)) {
u32 writeVal = PSB_RVDC32(reg);
writeVal |= (mask | (mask >> 16));
PSB_WVDC32(writeVal, reg);
(void) PSB_RVDC32(reg);
gma_power_end(dev_priv->dev);
}
}
}
So, if a flag in dev_priv->pipestat[pipe] is not in agreement with
dev->vblank[0].enabled,
we will have a call to gma_power_begin() again and got an unavoidable
deadlock.
Thus it seems either some code is unneeded at all or we could have a
deadlock from time to time.
What do you think?
Found by Linux Driver Verification project (linuxtesting.org).
--
Alexey Khoroshilov
Linux Verification Center, ISPRAS
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