Revision 2be23c475af8ae4e25f8bab08d815b17593bd547 authored by Russell King on 08 September 2010, 15:27:56 UTC, committed by Russell King on 08 September 2010, 15:27:56 UTC
Dave Hylands reports: | We've observed a problem with dma_alloc_writecombine when the system | is under heavy load (heavy bus traffic). We've managed to reduce the | problem to the following snippet, which is run from a kthread in a | continuous loop: | | void *virtAddr; | dma_addr_t physAddr; | unsigned int numBytes = 256; | | for (;;) { | virtAddr = dma_alloc_writecombine(NULL, | numBytes, &physAddr, GFP_KERNEL); | if (virtAddr == NULL) { | printk(KERN_ERR "Running out of memory\n"); | break; | } | | /* access DMA memory allocated */ | tmp = virtAddr; | *tmp = 0x77; | | /* free DMA memory */ | dma_free_writecombine(NULL, | numBytes, virtAddr, physAddr); | | ...sleep here... | } | | By itself, the code will run forever with no issues. However, as we | increase our bus traffic (typically using DMA) then the *tmp = 0x77 | line will eventually cause a page fault. If we add a small delay (a | few microseconds) before the *tmp = 0x77, then we don't see a page | fault, even under heavy load. A dsb() is required after modifying the PTE entries to ensure that they will always be visible. Add this dsb(). Reported-by: Dave Hylands <dhylands@gmail.com> Tested-by: Dave Hylands <dhylands@gmail.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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File | Mode | Size |
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Makefile | -rw-r--r-- | 394 bytes |
compat.c | -rw-r--r-- | 16.9 KB |
compat_mq.c | -rw-r--r-- | 4.0 KB |
ipc_sysctl.c | -rw-r--r-- | 5.1 KB |
ipcns_notifier.c | -rw-r--r-- | 2.2 KB |
mq_sysctl.c | -rw-r--r-- | 2.7 KB |
mqueue.c | -rw-r--r-- | 30.3 KB |
msg.c | -rw-r--r-- | 20.8 KB |
msgutil.c | -rw-r--r-- | 2.8 KB |
namespace.c | -rw-r--r-- | 3.3 KB |
sem.c | -rw-r--r-- | 40.3 KB |
shm.c | -rw-r--r-- | 25.8 KB |
syscall.c | -rw-r--r-- | 2.3 KB |
util.c | -rw-r--r-- | 22.9 KB |
util.h | -rw-r--r-- | 5.2 KB |
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