On Thu, Apr 14, 2016 at 10:12:53PM +0300, Dan Carpenter wrote: > On Thu, Apr 14, 2016 at 02:40:06PM -0400, Gabriel L. Somlo wrote: > > On Thu, Apr 14, 2016 at 12:33:37PM +0300, Dan Carpenter wrote: > > > It acpi_acquire_global_lock() return AE_NOT_CONFIGURED then "glk" isn't > > ^ ^ > > If returns > > > > > initialized, which, if you got very unlucky, could cause a bug. > > > > > > In principle I'm OK with being cautious and initializing local > > variables just in case, but I'm curious: > > > > acpi_acquire_global_lock() (and its friend, acpi_release_global_lock()) > > are both wrapped inside the same macro -- ACPI_HW_DEPENDENT_RETURN_STATUS > > -- which either makes them both do something useful, or makes them both > > no-ops returning a hardcoded AE_NOT_CONFIGURED. > > > > So what else do you think could be a way to get very unlucky ? > > If "glk" happened to to equal acpi_gbl_global_lock_handle by chance > then we would release it without acquiring it first. Actually I could > initialize it to zero and that would be better, no? No, because acpi_release_global_lock() would also be a hard-coded "return AE_NOT_CONFIGURED" by the same macro which also hard-coded acpi_acquire_global_lock() to be "return AE_NOT_CONFIGURED" in the first place. See include/acpi/acpixf.h, search for the two occurrences of "#define ACPI_HW_DEPENDENT_RETURN_STATUS" and then for: "global_lock" further down in the file. Whether both (or neither) of lock/unlock are for real or just hardcoded to return AE_NOT_CONFIGURED depends on ACPI_REDUCED_HARDWARE, which I assume is also set when there's *no* ACPI hardware at all. But I don't believe it's possible for "unlock" to do anything at all if "lock" was hardcoded to simply return AE_NOT_CONFIGURED. Then again, it's possible I'm still missing something :) Thanks, --Gabe -- To unsubscribe from this list: send the line "unsubscribe kernel-janitors" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
