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Re: [PATCH 0/3] THREAD_INFO_IN_TASK_STRUCT vs generic preemption code

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On Thu, Oct 13, 2016 at 4:57 AM, Heiko Carstens
<heiko.carstens@de.ibm.com> wrote:
> Commit c65eacbe290b ("sched/core: Allow putting thread_info into
> task_struct") made struct thread_info a generic struct with only a
> single flags member if THREAD_INFO_IN_TASK_STRUCT is selected.
>
> This change however seems to be quite x86 centric, since at least the
> generic preemption code (asm-generic/preempt.h) assumes that struct
> thread_info also has a preempt_count member, which apparently was not
> true for x86.
>
> We could add a bit more ifdefs to solve this problem too, but it seems
> to be much simpler to make struct thread_info arch specific
> again. This also makes the conversion to THREAD_INFO_IN_TASK_STRUCT a
> bit easier for architectures that have a couple of arch specific stuff
> in their thread_info definition.

OK, I give in.

But can you coordinate with Mark, because I think I convinced him to
do it a little differently?  I might be changing my mind a bit for an
evil reason.  Specifically, on x86_64, we could do the following evil,
horrible thing:

union {
  u64 flags;
  struct {
    u32 atomic_flags;
    u32 nonatomic_flags;
  }
};

Then we could read and test the full set of flags (currently split
between "flags" and "status") with a single instruction, and we could
set them maximally efficiently.  I don't actually want to do this
right away, but making thread_info fully arch-controlled would allow
this.

--Andy

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[PATCH 0/3] THREAD_INFO_IN_TASK_STRUCT vs generic preemption code Heiko Carstens <heiko.carstens@de.ibm.com> - 2016-10-13 14:50 +0200
  [PATCH 1/3] sched/core,x86: make struct thread_info arch specific again Heiko Carstens <heiko.carstens@de.ibm.com> - 2016-10-13 15:10 +0200
    Re: [PATCH 1/3] sched/core,x86: make struct thread_info arch  specific again Mark Rutland <mark.rutland@arm.com> - 2016-10-14 01:50 +0200
      Re: [PATCH 1/3] sched/core,x86: make struct thread_info arch specific again Andy Lutomirski <luto@amacapital.net> - 2016-10-14 02:00 +0200
  [PATCH 2/3] sched/preempt: include asm/current.h Heiko Carstens <heiko.carstens@de.ibm.com> - 2016-10-13 15:10 +0200
    Re: [PATCH 2/3] sched/preempt: include asm/current.h Mark Rutland <mark.rutland@arm.com> - 2016-10-14 01:30 +0200
      Re: [PATCH 2/3] sched/preempt: include asm/current.h Heiko Carstens <heiko.carstens@de.ibm.com> - 2016-10-14 10:20 +0200
        [PATCH] thread_info: include <current.h> for THREAD_INFO_IN_TASK (WAS: [PATCH 2/3] sched/preempt: include asm/current.h) Mark Rutland <mark.rutland@arm.com> - 2016-10-14 12:50 +0200
          Re: [PATCH] thread_info: include <current.h> for THREAD_INFO_IN_TASK  (WAS: [PATCH 2/3] sched/preempt: include asm/current.h) Mark Rutland <mark.rutland@arm.com> - 2016-10-17 16:50 +0200
            Re: [PATCH] thread_info: include <current.h> for THREAD_INFO_IN_TASK  (WAS: [PATCH 2/3] sched/preempt: include asm/current.h) Mark Rutland <mark.rutland@arm.com> - 2016-10-17 19:40 +0200
              Re: [PATCH] thread_info: include <current.h> for THREAD_INFO_IN_TASK  (WAS: [PATCH 2/3] sched/preempt: include asm/current.h) Heiko Carstens <heiko.carstens@de.ibm.com> - 2016-10-18 12:40 +0200
  [PATCH 3/3] s390: move thread_info into task_struct Heiko Carstens <heiko.carstens@de.ibm.com> - 2016-10-13 22:10 +0200
  Re: [PATCH 0/3] THREAD_INFO_IN_TASK_STRUCT vs generic preemption code Andy Lutomirski <luto@amacapital.net> - 2016-10-14 00:10 +0200

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