@@ -214,10 +214,11 @@ milbeaut_hdmac_chan_config(struct dma_chan *chan, struct dma_slave_config *cfg)
{
struct virt_dma_chan *vc = to_virt_chan(chan);
struct milbeaut_hdmac_chan *mc = to_milbeaut_hdmac_chan(vc);
+ unsigned long flags;
- spin_lock(&mc->vc.lock);
+ spin_lock_irqsave(&mc->vc.lock, flags);
mc->cfg = *cfg;
- spin_unlock(&mc->vc.lock);
+ spin_unlock_irqrestore(&mc->vc.lock, flags);
return 0;
}
@@ -226,13 +227,14 @@ static int milbeaut_hdmac_chan_pause(struct dma_chan *chan)
{
struct virt_dma_chan *vc = to_virt_chan(chan);
struct milbeaut_hdmac_chan *mc = to_milbeaut_hdmac_chan(vc);
+ unsigned long flags;
u32 val;
- spin_lock(&mc->vc.lock);
+ spin_lock_irqsave(&mc->vc.lock, flags);
val = readl_relaxed(mc->reg_ch_base + MLB_HDMAC_DMACA);
val |= MLB_HDMAC_PB;
writel_relaxed(val, mc->reg_ch_base + MLB_HDMAC_DMACA);
- spin_unlock(&mc->vc.lock);
+ spin_unlock_irqrestore(&mc->vc.lock, flags);
return 0;
}
@@ -241,13 +243,14 @@ static int milbeaut_hdmac_chan_resume(struct dma_chan *chan)
{
struct virt_dma_chan *vc = to_virt_chan(chan);
struct milbeaut_hdmac_chan *mc = to_milbeaut_hdmac_chan(vc);
+ unsigned long flags;
u32 val;
- spin_lock(&mc->vc.lock);
+ spin_lock_irqsave(&mc->vc.lock, flags);
val = readl_relaxed(mc->reg_ch_base + MLB_HDMAC_DMACA);
val &= ~MLB_HDMAC_PB;
writel_relaxed(val, mc->reg_ch_base + MLB_HDMAC_DMACA);
- spin_unlock(&mc->vc.lock);
+ spin_unlock_irqrestore(&mc->vc.lock, flags);
return 0;
}
As &mc->vc.lock is acquired by milbeaut_hdmac_interrupt() under irq context, other acquisition of the same lock under process context should disable irq, otherwise deadlock could happen if the irq preempts the execution of process context code while the lock is held in process context on the same CPU. milbeaut_hdmac_chan_config(), milbeaut_hdmac_chan_resume() and milbeaut_hdmac_chan_pause() are such callback functions not disable irq by default. Possible deadlock scenario: milbeaut_hdmac_chan_config() -> spin_lock(&mc->vc.lock) <hard interruption> -> milbeaut_hdmac_interrupt() -> spin_lock(&mc->vc.lock); (deadlock here) This flaw was found by an experimental static analysis tool I am developing for irq-related deadlock. The tentative patch fixes the potential deadlock by spin_lock_irqsave() in the three callback functions to disable irq while lock is held. Signed-off-by: Chengfeng Ye <dg573847474@gmail.com> --- drivers/dma/milbeaut-hdmac.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-)