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Fix potential deadlock in `make-struct'.

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* libguile/struct.c (scm_make_struct): Remove critical section, as
  suggested by Linas Vepstas <linasvepstas@gmail.com>.  See
  http://lists.gnu.org/archive/html/bug-guile/2008-11/msg00036.html for
  a discussion.
This commit is contained in:
Ludovic Courtès 2008-11-30 20:26:56 +01:00
parent d051899d17
commit cb823e630d
2 changed files with 9 additions and 10 deletions
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18
libguile/struct.c
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@ -449,8 +449,14 @@ SCM_DEFINE (scm_make_struct, "make-struct", 2, 0, 1,
if (! SCM_LAYOUT_TAILP (SCM_CHAR (last_char)))
goto bad_tail;
}
SCM_CRITICAL_SECTION_START;
/* In guile 1.8.5 and earlier, everything below was covered by a
CRITICAL_SECTION lock. This can lead to deadlocks in garbage
collection, since other threads might be holding the heap_mutex, while
sleeping on the CRITICAL_SECTION lock. There does not seem to be any
need for a lock on the section below, as it does not access or update
any globals, so the critical section has been removed. */
if (SCM_STRUCT_DATA (vtable)[scm_struct_i_flags] & SCM_STRUCTF_ENTITY)
{
data = scm_alloc_struct (basic_size + tail_elts,
@ -466,15 +472,7 @@ SCM_DEFINE (scm_make_struct, "make-struct", 2, 0, 1,
handle = scm_double_cell ((((scm_t_bits) SCM_STRUCT_DATA (vtable))
+ scm_tc3_struct),
(scm_t_bits) data, 0, 0);
SCM_CRITICAL_SECTION_END;
/* In guile 1.8.1 and earlier, the SCM_CRITICAL_SECTION_END above covered
also the following scm_struct_init. But that meant if scm_struct_init
finds an invalid type for a "u" field then there's an error throw in a
critical section, which results in an abort(). Not sure if we need any
protection across scm_struct_init. The data array contains garbage at
this point, but until we return it's not visible to anyone except
`gc'. */
scm_struct_init (handle, layout, data, tail_elts, init);
return handle;