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save errno in write barrier signal handler

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In case a write barrier happens between the set and use
of `errno`, make sure the barrier doesn't cause the
`errno` value to change in the process of making other
system calls.
This commit is contained in:
Matthew Flatt 2016-10-09 17:22:38 -06:00
parent 9422d66601
commit 6e2978fe5c
1 changed files with 4 additions and 0 deletions
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4
racket/src/racket/gc2/newgc.c
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@ -9,6 +9,7 @@
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include "platforms.h"
#include "../src/schpriv.h"
#include "gc2.h"
@ -1004,6 +1005,7 @@ static void set_has_back_pointers(NewGC *gc, mpage *page)
static int designate_modified_gc(NewGC *gc, void *p)
{
int saved_errno = errno; /* in case signal happens between set and use of errno */
mpage *page = pagemap_find_page(gc->page_maps, p);
if (gc->no_further_modifications) {
@ -1019,6 +1021,7 @@ static int designate_modified_gc(NewGC *gc, void *p)
|| (gc->doing_memory_accounting && gc->finished_incremental))) {
check_incremental_unprotect(gc, page);
gc->unprotected_page = 1; /* for using fuel */
errno = saved_errno;
return 1;
}
GCPRINT(GCOUTF, "Seg fault (internal error during gc) at %p\n", p);
@ -1031,6 +1034,7 @@ static int designate_modified_gc(NewGC *gc, void *p)
if (!page->back_pointers)
set_has_back_pointers(gc, page);
gc->modified_unprotects++;
errno = saved_errno;
return 1;
} else {
if (gc->primoridal_gc)