From 2e053a27d9d5ad5e0831e002cbf8043836fb2060 Mon Sep 17 00:00:00 2001 From: "B.J. Buchalter" Date: Mon, 2 May 2011 13:33:42 -0400 Subject: firewire: Fix for broken configrom updates in quick succession Current implementation of ohci_set_config_rom() uses a deferred bus reset via fw_schedule_bus_reset(). If clients add multiple unit descriptors to the config_rom in quick succession, the deferred bus reset may not have fired before succeeding update requests have come in. This can lead to an incorrect partial update of the config_rom for both addition and removal of config_rom descriptors, as the ohci_set_config_rom() routine will return -EBUSY if a previous pending update has not been completed yet; the requested update just gets dropped on the floor. This patch recognizes that the "in-flight" update can be modified until it has been processed by the bus-reset, and the locking in the bus_reset_tasklet ensures that the update is done atomically with respect to modifications made by ohci_set_config_rom(). The -EBUSY error case is simply removed. [Stefan R: The bug always existed at least theoretically. But it became easy to trigger since 2.6.36 commit 02d37bed188c "firewire: core: integrate software-forced bus resets with bus management" which introduced long mandatory delays between janitorial bus resets.] Signed-off-by: Benjamin Buchalter Signed-off-by: Stefan Richter (trivial style changes) Cc: # 2.6.36.y and newer --- drivers/firewire/ohci.c | 39 +++++++++++++++++++++++++-------------- 1 file changed, 25 insertions(+), 14 deletions(-) (limited to 'drivers/firewire') diff --git a/drivers/firewire/ohci.c b/drivers/firewire/ohci.c index f903d7b6f34a..23d1468ad253 100644 --- a/drivers/firewire/ohci.c +++ b/drivers/firewire/ohci.c @@ -2199,7 +2199,6 @@ static int ohci_set_config_rom(struct fw_card *card, { struct fw_ohci *ohci; unsigned long flags; - int ret = -EBUSY; __be32 *next_config_rom; dma_addr_t uninitialized_var(next_config_rom_bus); @@ -2240,22 +2239,37 @@ static int ohci_set_config_rom(struct fw_card *card, spin_lock_irqsave(&ohci->lock, flags); + /* + * If there is not an already pending config_rom update, + * push our new allocation into the ohci->next_config_rom + * and then mark the local variable as null so that we + * won't deallocate the new buffer. + * + * OTOH, if there is a pending config_rom update, just + * use that buffer with the new config_rom data, and + * let this routine free the unused DMA allocation. + */ + if (ohci->next_config_rom == NULL) { ohci->next_config_rom = next_config_rom; ohci->next_config_rom_bus = next_config_rom_bus; + next_config_rom = NULL; + } - copy_config_rom(ohci->next_config_rom, config_rom, length); + copy_config_rom(ohci->next_config_rom, config_rom, length); - ohci->next_header = config_rom[0]; - ohci->next_config_rom[0] = 0; + ohci->next_header = config_rom[0]; + ohci->next_config_rom[0] = 0; - reg_write(ohci, OHCI1394_ConfigROMmap, - ohci->next_config_rom_bus); - ret = 0; - } + reg_write(ohci, OHCI1394_ConfigROMmap, ohci->next_config_rom_bus); spin_unlock_irqrestore(&ohci->lock, flags); + /* If we didn't use the DMA allocation, delete it. */ + if (next_config_rom != NULL) + dma_free_coherent(ohci->card.device, CONFIG_ROM_SIZE, + next_config_rom, next_config_rom_bus); + /* * Now initiate a bus reset to have the changes take * effect. We clean up the old config rom memory and DMA @@ -2263,13 +2277,10 @@ static int ohci_set_config_rom(struct fw_card *card, * controller could need to access it before the bus reset * takes effect. */ - if (ret == 0) - fw_schedule_bus_reset(&ohci->card, true, true); - else - dma_free_coherent(ohci->card.device, CONFIG_ROM_SIZE, - next_config_rom, next_config_rom_bus); - return ret; + fw_schedule_bus_reset(&ohci->card, true, true); + + return 0; } static void ohci_send_request(struct fw_card *card, struct fw_packet *packet) -- cgit v1.2.3