code review 115280043: runtime: generate type info for chans

runtime: generate type info for chans

[dvyukov, 2014-07-29 11:51:43]

Hello golang-codereviews@googlegroups.com (cc: khr@golang.org),

I'd like you to review this change to
https://dvyukov%40google.com@code.google.com/p/go/

[khr1, 2014-07-29 16:48:28]

LGTM.


On Tue, Jul 29, 2014 at 4:51 AM, <dvyukov@google.com> wrote:

> Reviewers: golang-codereviews,
>
> Message:
> Hello golang-codereviews@googlegroups.com (cc: khr@golang.org),
>
> I'd like you to review this change to
> https://dvyukov%40google.com@code.google.com/p/go/
>
>
> Description:
> runtime: generate type info for chans
>
> Please review this at https://codereview.appspot.com/115280043/
>
> Affected files (+42, -9 lines):
>   M src/pkg/runtime/chan.h
>   M src/pkg/runtime/chan.goc
>   M src/pkg/runtime/proc.c
>   M src/pkg/runtime/runtime.h
>
>
> Index: src/pkg/runtime/chan.goc
> ===================================================================
> --- a/src/pkg/runtime/chan.goc
> +++ b/src/pkg/runtime/chan.goc
> @@ -9,16 +9,40 @@
>  #include "race.h"
>  #include "malloc.h"
>  #include "chan.h"
> +#include "mgc0.h"
> +#include "typekind.h"
>  #include "../../cmd/ld/textflag.h"
>
> -uint32 runtime·Hchansize = sizeof(Hchan);
> -
>  static void    dequeueg(WaitQ*);
>  static SudoG*  dequeue(WaitQ*);
>  static void    enqueue(WaitQ*, SudoG*);
> -static void    destroychan(Hchan*);
>  static void    racesync(Hchan*, SudoG*);
>
> +static Type    hchanType;
> +static String  hchanStr;
> +
> +void
> +runtime·chaninit(void)
> +{
> +       int32 i, off;
> +       byte *mask;
> +
> +       // Generate (bare minimum) type descriptor for Hchan.
> +       hchanType.size = sizeof(Hchan);
> +       hchanStr = runtime·gostringnocopy((byte*)"chan");
> +       hchanType.string = &hchanStr;
> +       // Hchan has only one interesting pointer -- buf.
> +       off = offsetof(Hchan, buf)/PtrSize*gcBits;
> +       if(off%8)
> +               runtime·throw("makechan: unaligned buffer");
> +       if(off+8 >= sizeof(hchanType.gc)*8)
> +               runtime·throw("makechan: gc mask does not fit");
> +       mask = (byte*)hchanType.gc;
> +       for(i = 0; i < off/8; i++)
> +               mask[i] = (BitsScalar<<2) | (BitsScalar<<6);
> +       mask[off/8] = (BitsPointer<<2) | (BitsDead<<6);
> +}
> +
>  static Hchan*
>  makechan(ChanType *t, int64 hint)
>  {
> @@ -36,8 +60,17 @@
>         if(hint < 0 || (intgo)hint != hint || (elem->size > 0 && hint >
> (MaxMem - sizeof(*c)) / elem->size))
>                 runtime·panicstring("makechan: size out of range");
>
> -       // allocate memory in one call
> -       c = (Hchan*)runtime·mallocgc(sizeof(*c) + hint*elem->size, nil,
> 0);
> +       if((elem->kind&KindNoPointers) || hint == 0) {
> +               // allocate memory in one call
> +               c = (Hchan*)runtime·mallocgc(sizeof(*c) +
> hint*elem->size, nil, FlagNoScan);
> +               if(hint > 0 && elem->size != 0)
> +                       c->buf = (byte*)(c+1);
> +               else
> +                       c->buf = (byte*)c;  // race detector uses this
> location for synchronization
> +       } else {
> +               c = (Hchan*)runtime·cnew(&hchanType);
> +               c->buf = runtime·cnewarray(elem, hint);
> +       }
>         c->elemsize = elem->size;
>         c->elemtype = elem;
>         c->dataqsiz = hint;
> Index: src/pkg/runtime/chan.h
> ===================================================================
> --- a/src/pkg/runtime/chan.h
> +++ b/src/pkg/runtime/chan.h
> @@ -26,14 +26,12 @@
>         SudoG*  last;
>  };
>
> -// The garbage collector is assuming that Hchan can only contain pointers
> into the stack
> -// and cannot contain pointers into the heap.
>  struct Hchan
>  {
>         uintgo  qcount;                 // total data in the q
>         uintgo  dataqsiz;               // size of the circular q
> +       byte*   buf;
>         uint16  elemsize;
> -       uint16  pad;                    // ensures proper alignment of the
> buffer that follows Hchan in memory
>         bool    closed;
>         Type*   elemtype;               // element type
>         uintgo  sendx;                  // send index
> @@ -45,7 +43,7 @@
>
>  // Buffer follows Hchan immediately in memory.
>  // chanbuf(c, i) is pointer to the i'th slot in the buffer.
> -#define chanbuf(c, i) ((byte*)((c)+1)+(uintptr)(c)->elemsize*(i))
> +#define chanbuf(c, i) ((byte*)((c)->buf)+(uintptr)(c)->elemsize*(i))
>
>  enum
>  {
> Index: src/pkg/runtime/proc.c
> ===================================================================
> --- a/src/pkg/runtime/proc.c
> +++ b/src/pkg/runtime/proc.c
> @@ -158,6 +158,7 @@
>         runtime·symtabinit();
>         runtime·stackinit();
>         runtime·mallocinit();
> +       runtime·chaninit();
>         mcommoninit(g->m);
>
>         // Initialize the itable value for newErrorCString,
> Index: src/pkg/runtime/runtime.h
> ===================================================================
> --- a/src/pkg/runtime/runtime.h
> +++ b/src/pkg/runtime/runtime.h
> @@ -862,6 +862,7 @@
>  MCache*        runtime·allocmcache(void);
>  void   runtime·freemcache(MCache*);
>  void   runtime·mallocinit(void);
> +void   runtime·chaninit(void);
>  bool   runtime·ifaceeq_c(Iface, Iface);
>  bool   runtime·efaceeq_c(Eface, Eface);
>  uintptr        runtime·ifacehash(Iface, uintptr);
>
>
>

[dvyukov, 2014-07-29 18:06:55]

*** Submitted as https://code.google.com/p/go/source/detail?r=6ced5a748d5e ***

runtime: generate type info for chans

LGTM=khr
R=golang-codereviews, khr
CC=golang-codereviews, khr
https://codereview.appspot.com/115280043