[PATCH] Improve pci_alloc_consistent wrapper on preemptive kernels

From: Andi Kleen (ak_at_suse.de)
Date: 07/30/04

  • Next message: Jeff Garzik: "Re: List of pending v2.4 kernel bugs" 
    Date:	Fri, 30 Jul 2004 19:02:27 +0200
To: akpm@osdl.org

    This is a minor optimization for the pci_alloc_consistent wrapper for
    the generic dma API. When the kernel is compiled preemptive the caller
    can decide if the allocation needs to be GFP_KERNEL or GFP_ATOMIC.

    I had this optimization previously in x86-64 private code, but it needs to move
    up now that x86-64 uses the generic DMA API.

    diff -urpN -X ../KDIFX linux-2.6.8rc2-mm1/include/asm-generic/pci-dma-compat.h linux-2.6.8rc2-mm1-amd64/include/asm-generic/pci-dma-compat.h
    --- linux-2.6.8rc2-mm1/include/asm-generic/pci-dma-compat.h 2004-04-06 13:12:19.000000000 +0200
    +++ linux-2.6.8rc2-mm1-amd64/include/asm-generic/pci-dma-compat.h 2004-07-30 17:02:49.000000000 +0200
    @@ -5,6 +5,13 @@
     #define _ASM_GENERIC_PCI_DMA_COMPAT_H
     
     #include <linux/dma-mapping.h>
    +#include <linux/config.h>
    +
    +#ifdef CONFIG_PREEMPT
    +#define preempt_atomic() in_atomic()
    +#else
    +#define preempt_atomic() 1
    +#endif
     
     /* note pci_set_dma_mask isn't here, since it's a public function
      * exported from drivers/pci, use dma_supported instead */
    @@ -15,11 +22,12 @@ pci_dma_supported(struct pci_dev *hwdev,
             return dma_supported(hwdev == NULL ? NULL : &hwdev->dev, mask);
     }
     
    +/* Would be better to move this out of line. It's already quite big. */
     static inline void *
     pci_alloc_consistent(struct pci_dev *hwdev, size_t size,
                          dma_addr_t *dma_handle)
     {
    - return dma_alloc_coherent(hwdev == NULL ? NULL : &hwdev->dev, size, dma_handle, GFP_ATOMIC);
    + return dma_alloc_coherent(hwdev == NULL ? NULL : &hwdev->dev, size, dma_handle, preempt_atomic() ? GFP_ATOMIC : GFP_KERNEL);
     }
     
     static inline void
    -
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