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From: Stefani Seibold <stefani@seibold.net> The use of a memcpy() during a spinlock operation will cause very long thread context switch delays if the flash chip bandwidth is low and the data to be copied large, because a spinlock will disable preemption. For example: A flash with 6,5 MB/s bandwidth will cause under ubifs, which request sometimes 128 KB (the flash erase size), a preemption delay of 20 milliseconds. High priority threads will not be served during this time, regardless whether this threads access the flash or not. This behavior breaks real time. The patch changes all the use of spin_lock operations for xxxx->mutex into mutex operations, which is exact what the name says and means. I have checked the code of the drivers and there is no use of atomic pathes like interrupt or timers. The mtdoops facility will also not be used by this drivers. So it is dave to replace the spin_lock against mutex. There is no performance regression since the mutex is normally not acquired. Changelog: 06.03.2010 First release 26.03.2010 Fix mutex[1] issue and tested it for compile failure Signed-off-by: Stefani Seibold <stefani@seibold.net> --- drivers/mtd/chips/cfi_cmdset_0001.c | 131 +++++++++++++++++----------------- drivers/mtd/chips/cfi_cmdset_0002.c | 122 ++++++++++++++++---------------- drivers/mtd/chips/cfi_cmdset_0020.c | 136 +++++++++++++++++----------------- drivers/mtd/chips/fwh_lock.h | 6 +- drivers/mtd/chips/gen_probe.c | 3 +- drivers/mtd/lpddr/lpddr_cmds.c | 79 ++++++++++---------- include/linux/mtd/flashchip.h | 4 +- 7 files changed, 239 insertions(+), 242 deletions(-) diff --git a/drivers/mtd/chips/cfi_cmdset_0001.c b/drivers/mtd/chips/cfi_cmdset_0001.c index 9253043..62f3ea9 100644 --- a/drivers/mtd/chips/cfi_cmdset_0001.c +++ b/drivers/mtd/chips/cfi_cmdset_0001.c @@ -725,8 +725,7 @@ static int cfi_intelext_partition_fixup(struct mtd_info *mtd, /* those should be reset too since they ...
Is the MTD mailing list routed to /dev/null? It is very sad that nobody gives my a reply. I ask for a merge for the patch, and if there any reason why not, it would be great to know. Otherwise i can't fix it. So again, please merge the path for the huge latency problem. --
Hi Andrew, David did not respond to my request since more than a month. Can u apply the patch to linux next? Thanks, Stefani --
The patch is rather too fundamental for there to be benefit in me carrying it. Hopefully Artem can look at it soon, although he's somewhat busy with real-life things at present. --
Yeah, the patch is in my l2 tree, and David should take it to mtd-2.6.git at some point, so it will probably be in 2.6.35, unless David misses the merge window :-) -- Best Regards, Artem Bityutskiy (Артём Битюцкий) --