Messages in this thread Patch in this message | | | Date | Thu, 16 Oct 2008 16:31:54 -0700 | From | Suresh Siddha <> | Subject | [patch 1/4] dmar: use spin_lock_irqsave() in qi_submit_sync() |
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From: Suresh Siddha <suresh.b.siddha@intel.com> Subject: use spin_lock_irqsave() in qi_submit_sync()
Next patch in the series will use queued invalidation interface qi_submit_sync() for DMA-remapping aswell, which can be called from interrupt context.
So use spin_lock_irqsave() instead of spin_lock() in qi_submit_sync().
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Signed-off-by: Youquan Song <youquan.song@intel.com> ---
Index: tip/drivers/pci/dmar.c =================================================================== --- tip.orig/drivers/pci/dmar.c 2008-10-07 15:42:47.000000000 -0700 +++ tip/drivers/pci/dmar.c 2008-10-07 16:27:47.000000000 -0700 @@ -592,11 +592,11 @@ hw = qi->desc; - spin_lock(&qi->q_lock); + spin_lock_irqsave(&qi->q_lock, flags); while (qi->free_cnt < 3) { - spin_unlock(&qi->q_lock); + spin_unlock_irqrestore(&qi->q_lock, flags); cpu_relax(); - spin_lock(&qi->q_lock); + spin_lock_irqsave(&qi->q_lock, flags); } index = qi->free_head; @@ -617,15 +617,22 @@ qi->free_head = (qi->free_head + 2) % QI_LENGTH; qi->free_cnt -= 2; - spin_lock_irqsave(&iommu->register_lock, flags); + spin_lock(&iommu->register_lock); /* * update the HW tail register indicating the presence of * new descriptors. */ writel(qi->free_head << 4, iommu->reg + DMAR_IQT_REG); - spin_unlock_irqrestore(&iommu->register_lock, flags); + spin_unlock(&iommu->register_lock); while (qi->desc_status[wait_index] != QI_DONE) { + /* + * We will leave the interrupts disabled, to prevent interrupt + * context to queue another cmd while a cmd is already submitted + * and waiting for completion on this cpu. This is to avoid + * a deadlock where the interrupt context can wait indefinitely + * for free slots in the queue. + */ spin_unlock(&qi->q_lock); cpu_relax(); spin_lock(&qi->q_lock); @@ -634,7 +641,7 @@ qi->desc_status[index] = QI_DONE; reclaim_free_desc(qi); - spin_unlock(&qi->q_lock); + spin_unlock_irqrestore(&qi->q_lock, flags); } /* --
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