Hello Lee, On Wed, Jun 13, 2007 at 01:02:04PM -0400, Lee Schermerhorn wrote: > Stephane: > > I need to add a flag to the ia64 thread info flags to support my > automigration work. I was using TIF_NOTIFY_RESUME which you removed. I > didn't notice that happening, but even if I did, I couldn't/wouldn't > have objected because my patches are still [maybe always?] out of tree. > Welcome to my world! I remove TIF_NOTIFY_RESUME because it was unused on all but IA-64. And there it was used by perfmon (v2.0) which I replace by a more explicit TIF flag. > Now, I've tried to add an automigration-specific flag, called > TIF_MIGRATION_WORK--to the flags to trigger entry to do_notify_resume() > to handle auto-migration. However, I'm getting errors from the > assembler in arch/ia64/kernel/fsys.S where ever the instruction: > > and r?=TIF_ALLWORK_MASK,r? > > occurs, complaining that "Operand 2 of 'and' should be an 8-bit integer > (-128-127)". This is worrisome to begin with, as thread information > flags comment says that "pending work-to-be-done flags are in > least-significant 16 bits", while the code currently only supports > "8-bits". What's more interesting is that I've used bit '7' for the > TIF_MIGRATION_WORK flag. That should fit in the range (-128 - 127), > right? Maybe the assembler is confused by sign extension of the signed > 8-bit int? > Funny! I went through exactly the same thought process when I remove the TIF flag. Yes, the instruction say imm8, so you'd expect that a 8-bit constant would fit. But, if you look closer and especially to the pseudo-code describing the instruction you'll see that there is sign-extension going on, so the assembler is not wrong. What I do not understand is what's the point of sign-extension on a AND (bitwise) operation? > For my testing, I can probably use your 'PERFMON_WORK flag, but that's > probably not a good long term solution. Any ideas how to proceed longer > term to support >7 pending work flags? > In anycase, there is no solution to your problem but to modify entry.S to deal with the bit-width limitation, i.e, you need to load the constant into a register and then do the and. You probably understand now, why I thought is was easier to remove unused TIF flags.... -- -Stephane - To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
|