Hi All, On one of my machines I noticed the following errors being logged: [ 52.892807] i2c i2c-0: adapter quirk: no zero length (addr 0x0078, size 0, read) [ 52.893037] i2c i2c-0: i2c read 0 bytes from client@0x78 starting at reg 0x0 failed, error: -95 The second line is coming from the Linux I2C ACPI OpRegion handling and after a bunch of debugging I've found out that there is a rather obvious (once you see it) and nasty race condition in the handling of I2C and GPIO opregions in acpi_ev_address_space_dispatch(). See the first patch in this series (the second patch is a follow-up cleanup patch removing some code duplication). TBH I'm surprised that this issue has gone unnoticed as long as it has, but I guess that it mostly leads to unreproducable sporadic problems making it hard to debug and I got lucky that I had a machine where the race seems to trigger about once every 20 seconds. I know that ACPICA patches are normally merged through the ACPICA upstream but given that this is a serious bug, I believe that in this case it might be best to add the fix directly to Linux and then port it to ACPICA from there. Regards, Hans
