* Re: Kludge in eval.c
[not found] <8337hvfs7j.fsf@gnu.org>
@ 2016-12-11 18:36 ` Noam Postavsky
2016-12-12 17:40 ` Eli Zaretskii
0 siblings, 1 reply; 3+ messages in thread
From: Noam Postavsky @ 2016-12-11 18:36 UTC (permalink / raw)
To: Eli Zaretskii, Emacs developers
[-- Attachment #1: Type: text/plain, Size: 1282 bytes --]
On Sat, Dec 10, 2016 at 3:24 PM, Eli Zaretskii <eliz@gnu.org> wrote:
>
> When I worked on merging the concurrency branch, I bumped into a
> problem with the recently introduced watcher feature. The problem is
> that variables can have thread-local bindings, so when there's a
> thread switch, Emacs needs to rebind those variables to the values
> they have in the new thread. If such a variable is marked as
> trap-write, rebinding would normally call the watchers, which I think
> is not what we want. Do you agree?
Yes, I agree. The fact that thread-local values are implemented by
rebinding is a C level implementation detail that shouldn't leak into
Lisp code.
>
> If you agree, then we need a way of bypassing the watchers call when
> the rebinding is due to a thread switch. In the merged concurrency
> code I used a semi-kludgey solution for that, see the two FIXMEs I
> left behind, in rebind_for_thread_switch and unbind_for_thread_switch.
> Could you please look at that and suggest a cleaner solution?
>
The easiest is adding a global flag, but after doing that, I realized
adding a parameter to set_internal and friends isn't too much trouble.
So my suggestion is the attached v2 patch, I've included the v1 for
comparison, since I had written it already anyway.
[-- Attachment #2: v1-0001-Clean-up-var-watcher-disabling-on-thread-switchin.patch --]
[-- Type: text/x-diff, Size: 4311 bytes --]
From 8e4e6cd9414e0ba301aad7ec24c3d01d67d391b7 Mon Sep 17 00:00:00 2001
From: Noam Postavsky <npostavs@gmail.com>
Date: Sat, 10 Dec 2016 21:53:53 -0500
Subject: [PATCH v1] Clean up var watcher disabling on thread switching
* src/data.c (inhibit_variable_watchers): New variable.
(notify_variable_watchers): Don't notify watchers it's non-nil.
* src/eval.c (set_inhibit_variable_watchers): New function.
(rebind_for_thread_switch, unbind_for_thread_switch): Disable variable
watchers while setting variables to thread-local values.
---
src/data.c | 4 ++++
src/eval.c | 39 +++++++++++++++++++++------------------
src/lisp.h | 1 +
3 files changed, 26 insertions(+), 18 deletions(-)
diff --git a/src/data.c b/src/data.c
index 09d94f5..682a669 100644
--- a/src/data.c
+++ b/src/data.c
@@ -1513,12 +1513,16 @@ DEFUN ("get-variable-watchers", Fget_variable_watchers, Sget_variable_watchers,
: Qnil;
}
+bool inhibit_variable_watchers = false;
+
void
notify_variable_watchers (Lisp_Object symbol,
Lisp_Object newval,
Lisp_Object operation,
Lisp_Object where)
{
+ if (inhibit_variable_watchers) return;
+
symbol = Findirect_variable (symbol);
ptrdiff_t count = SPECPDL_INDEX ();
diff --git a/src/eval.c b/src/eval.c
index f1e0ae7..15ef5ab 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -3343,30 +3343,34 @@ record_unwind_protect_void (void (*function) (void))
grow_specpdl ();
}
+static void
+set_inhibit_variable_watchers (int val)
+{
+ inhibit_variable_watchers = val;
+}
+
void
rebind_for_thread_switch (void)
{
union specbinding *bind;
+ ptrdiff_t count = SPECPDL_INDEX ();
+ record_unwind_protect_int (set_inhibit_variable_watchers,
+ inhibit_variable_watchers);
+ /* Hide implementation of thread-local variables from Lisp code. */
+ inhibit_variable_watchers = true;
+
for (bind = specpdl; bind != specpdl_ptr; ++bind)
{
if (bind->kind >= SPECPDL_LET)
{
Lisp_Object value = specpdl_saved_value (bind);
Lisp_Object sym = specpdl_symbol (bind);
- bool was_trapped =
- SYMBOLP (sym)
- && XSYMBOL (sym)->trapped_write == SYMBOL_TRAPPED_WRITE;
- /* FIXME: This is not clean, and if do_specbind signals an
- error, the symbol will be left untrapped. */
- if (was_trapped)
- XSYMBOL (sym)->trapped_write = SYMBOL_UNTRAPPED_WRITE;
bind->let.saved_value = Qnil;
do_specbind (XSYMBOL (sym), bind, value);
- if (was_trapped)
- XSYMBOL (sym)->trapped_write = SYMBOL_TRAPPED_WRITE;
}
}
+ unbind_to (count, Qnil);
}
static void
@@ -3510,24 +3514,23 @@ unbind_for_thread_switch (struct thread_state *thr)
{
union specbinding *bind;
+ ptrdiff_t count = SPECPDL_INDEX ();
+ record_unwind_protect_int (set_inhibit_variable_watchers,
+ inhibit_variable_watchers);
+ /* Hide implementation of thread-local variables from Lisp code. */
+ inhibit_variable_watchers = true;
+
+
for (bind = thr->m_specpdl_ptr; bind > thr->m_specpdl;)
{
if ((--bind)->kind >= SPECPDL_LET)
{
Lisp_Object sym = specpdl_symbol (bind);
- bool was_trapped =
- SYMBOLP (sym)
- && XSYMBOL (sym)->trapped_write == SYMBOL_TRAPPED_WRITE;
bind->let.saved_value = find_symbol_value (sym);
- /* FIXME: This is not clean, and if do_one_unbind signals an
- error, the symbol will be left untrapped. */
- if (was_trapped)
- XSYMBOL (sym)->trapped_write = SYMBOL_UNTRAPPED_WRITE;
do_one_unbind (bind, false);
- if (was_trapped)
- XSYMBOL (sym)->trapped_write = SYMBOL_TRAPPED_WRITE;
}
}
+ unbind_to (count, Qnil);
}
DEFUN ("special-variable-p", Fspecial_variable_p, Sspecial_variable_p, 1, 1, 0,
diff --git a/src/lisp.h b/src/lisp.h
index 252707c..b16cada 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -605,6 +605,7 @@ INLINE bool (VECTORLIKEP) (Lisp_Object);
/* Defined in data.c. */
extern _Noreturn void wrong_type_argument (Lisp_Object, Lisp_Object);
extern _Noreturn void wrong_choice (Lisp_Object, Lisp_Object);
+extern bool inhibit_variable_watchers;
extern void notify_variable_watchers (Lisp_Object symbol, Lisp_Object newval,
Lisp_Object operation, Lisp_Object where);
--
2.9.3
[-- Attachment #3: v2-0001-Clean-up-var-watcher-disabling-on-thread-switchin.patch --]
[-- Type: text/x-diff, Size: 11603 bytes --]
From 5c1680205ca0fc90ecf45afcb045d7d8457a1b3a Mon Sep 17 00:00:00 2001
From: Noam Postavsky <npostavs@gmail.com>
Date: Sun, 11 Dec 2016 13:08:15 -0500
Subject: [PATCH v2] Clean up var watcher disabling on thread switching
* src/data.c (Fset_default): Move code into new C level function,
`set_default_internal'.
(set_default_internal): New function, like `Fset_default' but also takes
additional bindflag parameter.
(set_internal): Only call `notify_variable_watchers' if bindflag is not
SET_INTERNAL_THREAD_SWITCH.
* src/eval.c (do_specbind, do_one_unbind): Add bindflag parameter,
passed on to set_internal and set_default_internal. Adjust callers.
(rebind_for_thread_switch, unbind_for_thread_switch): Pass
SET_INTERNAL_THREAD_SWITCH to do_specbind, do_one_unbind instead of
temporarily adjusting symbol's trapped_write field.
---
src/data.c | 46 +++++++++++++++++++++++++++++-----------------
src/eval.c | 51 ++++++++++++++++++---------------------------------
src/lisp.h | 6 +++++-
3 files changed, 52 insertions(+), 51 deletions(-)
diff --git a/src/data.c b/src/data.c
index 09d94f5..962648b 100644
--- a/src/data.c
+++ b/src/data.c
@@ -1296,11 +1296,13 @@ set_internal (Lisp_Object symbol, Lisp_Object newval, Lisp_Object where,
return;
case SYMBOL_TRAPPED_WRITE:
- notify_variable_watchers (symbol, voide? Qnil : newval,
- (bindflag == SET_INTERNAL_BIND? Qlet :
- bindflag == SET_INTERNAL_UNBIND? Qunlet :
- voide? Qmakunbound : Qset),
- where);
+ /* Setting due to thread-switching doesn't count. */
+ if (bindflag != SET_INTERNAL_THREAD_SWITCH)
+ notify_variable_watchers (symbol, voide? Qnil : newval,
+ (bindflag == SET_INTERNAL_BIND? Qlet :
+ bindflag == SET_INTERNAL_UNBIND? Qunlet :
+ voide? Qmakunbound : Qset),
+ where);
/* FALLTHROUGH! */
case SYMBOL_UNTRAPPED_WRITE:
break;
@@ -1411,7 +1413,7 @@ set_internal (Lisp_Object symbol, Lisp_Object newval, Lisp_Object where,
int offset = XBUFFER_OBJFWD (innercontents)->offset;
int idx = PER_BUFFER_IDX (offset);
if (idx > 0
- && !bindflag
+ && bindflag == SET_INTERNAL_SET
&& !let_shadows_buffer_binding_p (sym))
SET_PER_BUFFER_VALUE_P (buf, idx, 1);
}
@@ -1631,11 +1633,9 @@ DEFUN ("default-value", Fdefault_value, Sdefault_value, 1, 1, 0,
xsignal1 (Qvoid_variable, symbol);
}
-DEFUN ("set-default", Fset_default, Sset_default, 2, 2, 0,
- doc: /* Set SYMBOL's default value to VALUE. SYMBOL and VALUE are evaluated.
-The default value is seen in buffers that do not have their own values
-for this variable. */)
- (Lisp_Object symbol, Lisp_Object value)
+void
+set_default_internal (Lisp_Object symbol, Lisp_Object value,
+ enum Set_Internal_Bind bindflag)
{
struct Lisp_Symbol *sym;
@@ -1649,11 +1649,13 @@ DEFUN ("set-default", Fset_default, Sset_default, 2, 2, 0,
xsignal1 (Qsetting_constant, symbol);
else
/* Allow setting keywords to their own value. */
- return value;
+ return;
case SYMBOL_TRAPPED_WRITE:
/* Don't notify here if we're going to call Fset anyway. */
- if (sym->redirect != SYMBOL_PLAINVAL)
+ if (sym->redirect != SYMBOL_PLAINVAL
+ /* Setting due to thread switching doesn't count. */
+ && bindflag != SET_INTERNAL_THREAD_SWITCH)
notify_variable_watchers (symbol, value, Qset_default, Qnil);
/* FALLTHROUGH! */
case SYMBOL_UNTRAPPED_WRITE:
@@ -1666,7 +1668,7 @@ DEFUN ("set-default", Fset_default, Sset_default, 2, 2, 0,
switch (sym->redirect)
{
case SYMBOL_VARALIAS: sym = indirect_variable (sym); goto start;
- case SYMBOL_PLAINVAL: return Fset (symbol, value);
+ case SYMBOL_PLAINVAL: set_internal (symbol, value, Qnil, bindflag); return;
case SYMBOL_LOCALIZED:
{
struct Lisp_Buffer_Local_Value *blv = SYMBOL_BLV (sym);
@@ -1677,7 +1679,7 @@ DEFUN ("set-default", Fset_default, Sset_default, 2, 2, 0,
/* If the default binding is now loaded, set the REALVALUE slot too. */
if (blv->fwd && EQ (blv->defcell, blv->valcell))
store_symval_forwarding (blv->fwd, value, NULL);
- return value;
+ return;
}
case SYMBOL_FORWARDED:
{
@@ -1703,15 +1705,25 @@ DEFUN ("set-default", Fset_default, Sset_default, 2, 2, 0,
if (!PER_BUFFER_VALUE_P (b, idx))
set_per_buffer_value (b, offset, value);
}
- return value;
}
else
- return Fset (symbol, value);
+ set_internal (symbol, value, Qnil, bindflag);
+ return;
}
default: emacs_abort ();
}
}
+DEFUN ("set-default", Fset_default, Sset_default, 2, 2, 0,
+ doc: /* Set SYMBOL's default value to VALUE. SYMBOL and VALUE are evaluated.
+The default value is seen in buffers that do not have their own values
+for this variable. */)
+ (Lisp_Object symbol, Lisp_Object value)
+{
+ set_default_internal (symbol, value, SET_INTERNAL_SET);
+ return value;
+}
+
DEFUN ("setq-default", Fsetq_default, Ssetq_default, 0, UNEVALLED, 0,
doc: /* Set the default value of variable VAR to VALUE.
VAR, the variable name, is literal (not evaluated);
diff --git a/src/eval.c b/src/eval.c
index f1e0ae7..7e19df8 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -3197,7 +3197,7 @@ let_shadows_global_binding_p (Lisp_Object symbol)
static void
do_specbind (struct Lisp_Symbol *sym, union specbinding *bind,
- Lisp_Object value)
+ Lisp_Object value, enum Set_Internal_Bind bindflag)
{
switch (sym->redirect)
{
@@ -3205,19 +3205,19 @@ do_specbind (struct Lisp_Symbol *sym, union specbinding *bind,
if (!sym->trapped_write)
SET_SYMBOL_VAL (sym, value);
else
- set_internal (specpdl_symbol (bind), value, Qnil, SET_INTERNAL_BIND);
+ set_internal (specpdl_symbol (bind), value, Qnil, bindflag);
break;
case SYMBOL_FORWARDED:
if (BUFFER_OBJFWDP (SYMBOL_FWD (sym))
&& specpdl_kind (bind) == SPECPDL_LET_DEFAULT)
{
- Fset_default (specpdl_symbol (bind), value);
+ set_default_internal (specpdl_symbol (bind), value, bindflag);
return;
}
/* FALLTHROUGH */
case SYMBOL_LOCALIZED:
- set_internal (specpdl_symbol (bind), value, Qnil, SET_INTERNAL_BIND);
+ set_internal (specpdl_symbol (bind), value, Qnil, bindflag);
break;
default:
@@ -3258,7 +3258,7 @@ specbind (Lisp_Object symbol, Lisp_Object value)
specpdl_ptr->let.old_value = SYMBOL_VAL (sym);
specpdl_ptr->let.saved_value = Qnil;
grow_specpdl ();
- do_specbind (sym, specpdl_ptr - 1, value);
+ do_specbind (sym, specpdl_ptr - 1, value, SET_INTERNAL_BIND);
break;
case SYMBOL_LOCALIZED:
if (SYMBOL_BLV (sym)->frame_local)
@@ -3291,7 +3291,7 @@ specbind (Lisp_Object symbol, Lisp_Object value)
{
specpdl_ptr->let.kind = SPECPDL_LET_DEFAULT;
grow_specpdl ();
- do_specbind (sym, specpdl_ptr - 1, value);
+ do_specbind (sym, specpdl_ptr - 1, value, SET_INTERNAL_BIND);
return;
}
}
@@ -3299,7 +3299,7 @@ specbind (Lisp_Object symbol, Lisp_Object value)
specpdl_ptr->let.kind = SPECPDL_LET;
grow_specpdl ();
- do_specbind (sym, specpdl_ptr - 1, value);
+ do_specbind (sym, specpdl_ptr - 1, value, SET_INTERNAL_BIND);
break;
}
default: emacs_abort ();
@@ -3354,23 +3354,16 @@ rebind_for_thread_switch (void)
{
Lisp_Object value = specpdl_saved_value (bind);
Lisp_Object sym = specpdl_symbol (bind);
- bool was_trapped =
- SYMBOLP (sym)
- && XSYMBOL (sym)->trapped_write == SYMBOL_TRAPPED_WRITE;
- /* FIXME: This is not clean, and if do_specbind signals an
- error, the symbol will be left untrapped. */
- if (was_trapped)
- XSYMBOL (sym)->trapped_write = SYMBOL_UNTRAPPED_WRITE;
bind->let.saved_value = Qnil;
- do_specbind (XSYMBOL (sym), bind, value);
- if (was_trapped)
- XSYMBOL (sym)->trapped_write = SYMBOL_TRAPPED_WRITE;
+ do_specbind (XSYMBOL (sym), bind, value,
+ SET_INTERNAL_THREAD_SWITCH);
}
}
}
static void
-do_one_unbind (union specbinding *this_binding, bool unwinding)
+do_one_unbind (union specbinding *this_binding, bool unwinding,
+ enum Set_Internal_Bind bindflag)
{
eassert (unwinding || this_binding->kind >= SPECPDL_LET);
switch (this_binding->kind)
@@ -3399,7 +3392,7 @@ do_one_unbind (union specbinding *this_binding, bool unwinding)
SET_SYMBOL_VAL (XSYMBOL (sym), specpdl_old_value (this_binding));
else
set_internal (sym, specpdl_old_value (this_binding),
- Qnil, SET_INTERNAL_UNBIND);
+ Qnil, bindflag);
break;
}
else
@@ -3409,8 +3402,9 @@ do_one_unbind (union specbinding *this_binding, bool unwinding)
}
}
case SPECPDL_LET_DEFAULT:
- Fset_default (specpdl_symbol (this_binding),
- specpdl_old_value (this_binding));
+ set_default_internal (specpdl_symbol (this_binding),
+ specpdl_old_value (this_binding),
+ bindflag);
break;
case SPECPDL_LET_LOCAL:
{
@@ -3422,7 +3416,7 @@ do_one_unbind (union specbinding *this_binding, bool unwinding)
/* If this was a local binding, reset the value in the appropriate
buffer, but only if that buffer's binding still exists. */
if (!NILP (Flocal_variable_p (symbol, where)))
- set_internal (symbol, old_value, where, SET_INTERNAL_UNBIND);
+ set_internal (symbol, old_value, where, bindflag);
}
break;
}
@@ -3496,7 +3490,7 @@ unbind_to (ptrdiff_t count, Lisp_Object value)
union specbinding this_binding;
this_binding = *--specpdl_ptr;
- do_one_unbind (&this_binding, true);
+ do_one_unbind (&this_binding, true, SET_INTERNAL_UNBIND);
}
if (NILP (Vquit_flag) && !NILP (quitf))
@@ -3515,17 +3509,8 @@ unbind_for_thread_switch (struct thread_state *thr)
if ((--bind)->kind >= SPECPDL_LET)
{
Lisp_Object sym = specpdl_symbol (bind);
- bool was_trapped =
- SYMBOLP (sym)
- && XSYMBOL (sym)->trapped_write == SYMBOL_TRAPPED_WRITE;
bind->let.saved_value = find_symbol_value (sym);
- /* FIXME: This is not clean, and if do_one_unbind signals an
- error, the symbol will be left untrapped. */
- if (was_trapped)
- XSYMBOL (sym)->trapped_write = SYMBOL_UNTRAPPED_WRITE;
- do_one_unbind (bind, false);
- if (was_trapped)
- XSYMBOL (sym)->trapped_write = SYMBOL_TRAPPED_WRITE;
+ do_one_unbind (bind, false, SET_INTERNAL_THREAD_SWITCH);
}
}
}
diff --git a/src/lisp.h b/src/lisp.h
index 252707c..5b77dc8 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -3493,10 +3493,14 @@ set_sub_char_table_contents (Lisp_Object table, ptrdiff_t idx, Lisp_Object val)
enum Set_Internal_Bind {
SET_INTERNAL_SET,
SET_INTERNAL_BIND,
- SET_INTERNAL_UNBIND
+ SET_INTERNAL_UNBIND,
+ SET_INTERNAL_THREAD_SWITCH
};
extern void set_internal (Lisp_Object, Lisp_Object, Lisp_Object,
enum Set_Internal_Bind);
+extern void set_default_internal (Lisp_Object, Lisp_Object,
+ enum Set_Internal_Bind bindflag);
+
extern void syms_of_data (void);
extern void swap_in_global_binding (struct Lisp_Symbol *);
--
2.9.3
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: Kludge in eval.c
2016-12-11 18:36 ` Kludge in eval.c Noam Postavsky
@ 2016-12-12 17:40 ` Eli Zaretskii
2016-12-13 2:46 ` Noam Postavsky
0 siblings, 1 reply; 3+ messages in thread
From: Eli Zaretskii @ 2016-12-12 17:40 UTC (permalink / raw)
To: Noam Postavsky; +Cc: emacs-devel
> From: Noam Postavsky <npostavs@users.sourceforge.net>
> Date: Sun, 11 Dec 2016 13:36:25 -0500
>
> > When I worked on merging the concurrency branch, I bumped into a
> > problem with the recently introduced watcher feature. The problem is
> > that variables can have thread-local bindings, so when there's a
> > thread switch, Emacs needs to rebind those variables to the values
> > they have in the new thread. If such a variable is marked as
> > trap-write, rebinding would normally call the watchers, which I think
> > is not what we want. Do you agree?
>
> Yes, I agree. The fact that thread-local values are implemented by
> rebinding is a C level implementation detail that shouldn't leak into
> Lisp code.
>
> >
> > If you agree, then we need a way of bypassing the watchers call when
> > the rebinding is due to a thread switch. In the merged concurrency
> > code I used a semi-kludgey solution for that, see the two FIXMEs I
> > left behind, in rebind_for_thread_switch and unbind_for_thread_switch.
> > Could you please look at that and suggest a cleaner solution?
> >
>
> The easiest is adding a global flag, but after doing that, I realized
> adding a parameter to set_internal and friends isn't too much trouble.
> So my suggestion is the attached v2 patch, I've included the v1 for
> comparison, since I had written it already anyway.
Thanks, please push your v2.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Kludge in eval.c
2016-12-12 17:40 ` Eli Zaretskii
@ 2016-12-13 2:46 ` Noam Postavsky
0 siblings, 0 replies; 3+ messages in thread
From: Noam Postavsky @ 2016-12-13 2:46 UTC (permalink / raw)
To: Eli Zaretskii; +Cc: Emacs developers
On Mon, Dec 12, 2016 at 12:40 PM, Eli Zaretskii <eliz@gnu.org> wrote:
>
> Thanks, please push your v2.
Pushed as f66174a
^ permalink raw reply [flat|nested] 3+ messages in thread
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2016-12-11 18:36 ` Kludge in eval.c Noam Postavsky
2016-12-12 17:40 ` Eli Zaretskii
2016-12-13 2:46 ` Noam Postavsky
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