forked from luck/tmp_suning_uos_patched
2be23c475a
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>
|
||
|---|---|---|
| .. | ||
| abort-ev4.S | ||
| abort-ev4t.S | ||
| abort-ev5t.S | ||
| abort-ev5tj.S | ||
| abort-ev6.S | ||
| abort-ev7.S | ||
| abort-lv4t.S | ||
| abort-macro.S | ||
| abort-nommu.S | ||
| alignment.c | ||
| cache-fa.S | ||
| cache-feroceon-l2.c | ||
| cache-l2x0.c | ||
| cache-tauros2.c | ||
| cache-v3.S | ||
| cache-v4.S | ||
| cache-v4wb.S | ||
| cache-v4wt.S | ||
| cache-v6.S | ||
| cache-v7.S | ||
| cache-xsc3l2.c | ||
| context.c | ||
| copypage-fa.c | ||
| copypage-feroceon.c | ||
| copypage-v3.c | ||
| copypage-v4mc.c | ||
| copypage-v4wb.c | ||
| copypage-v4wt.c | ||
| copypage-v6.c | ||
| copypage-xsc3.c | ||
| copypage-xscale.c | ||
| dma-mapping.c | ||
| extable.c | ||
| fault-armv.c | ||
| fault.c | ||
| fault.h | ||
| flush.c | ||
| highmem.c | ||
| init.c | ||
| iomap.c | ||
| ioremap.c | ||
| Kconfig | ||
| Makefile | ||
| mm.h | ||
| mmap.c | ||
| mmu.c | ||
| nommu.c | ||
| pabort-legacy.S | ||
| pabort-v6.S | ||
| pabort-v7.S | ||
| pgd.c | ||
| proc-arm6_7.S | ||
| proc-arm7tdmi.S | ||
| proc-arm9tdmi.S | ||
| proc-arm720.S | ||
| proc-arm740.S | ||
| proc-arm920.S | ||
| proc-arm922.S | ||
| proc-arm925.S | ||
| proc-arm926.S | ||
| proc-arm940.S | ||
| proc-arm946.S | ||
| proc-arm1020.S | ||
| proc-arm1020e.S | ||
| proc-arm1022.S | ||
| proc-arm1026.S | ||
| proc-fa526.S | ||
| proc-feroceon.S | ||
| proc-macros.S | ||
| proc-mohawk.S | ||
| proc-sa110.S | ||
| proc-sa1100.S | ||
| proc-syms.c | ||
| proc-v6.S | ||
| proc-v7.S | ||
| proc-xsc3.S | ||
| proc-xscale.S | ||
| tlb-fa.S | ||
| tlb-v3.S | ||
| tlb-v4.S | ||
| tlb-v4wb.S | ||
| tlb-v4wbi.S | ||
| tlb-v6.S | ||
| tlb-v7.S | ||
| vmregion.c | ||
| vmregion.h | ||