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WIP stack scrubbing #10725

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WIP stack scrubbing #10725

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ae7f75f
scrub everything that looks like a pointer to dead data on the stack
carnaval Apr 1, 2015
b0c99be
make it actually work. also revert Jameson's fix.
carnaval Apr 2, 2015
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52 changes: 42 additions & 10 deletions src/gc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -207,15 +207,15 @@ typedef struct _gcpage_t {
// A region is contiguous storage for up to REGION_PG_COUNT naturally aligned GC_PAGE_SZ pages
// It uses a very naive allocator (see malloc_page & free_page)
#if defined(_P64) && !defined(_COMPILER_MICROSOFT_)
#define REGION_PG_COUNT 16*8*4096 // 8G because virtual memory is cheap
#define REGION_PG_COUNT ((size_t)16*8*4096) // 8G because virtual memory is cheap
#else
#define REGION_PG_COUNT 8*4096 // 512M
#define REGION_PG_COUNT ((size_t)8*4096) // 512M
#endif
#define REGION_COUNT 8

typedef struct {
uint32_t freemap[REGION_PG_COUNT/32];
char pages[REGION_PG_COUNT][GC_PAGE_SZ];
uint32_t freemap[REGION_PG_COUNT/32];
gcpage_t meta[REGION_PG_COUNT];
} region_t;
static region_t *regions[REGION_COUNT] = {NULL};
Expand All @@ -236,14 +236,16 @@ static region_t *find_region(void *ptr)
{
// on 64bit systems we could probably use a single region and remove this loop
for (int i = 0; i < REGION_COUNT && regions[i]; i++) {
if ((char*)ptr >= (char*)regions[i] && (char*)ptr <= (char*)regions[i] + sizeof(region_t))
char* begin = &regions[i]->pages[0][0];
if ((char*)ptr >= begin && (char*)ptr < begin+REGION_PG_COUNT*GC_PAGE_SZ)
return regions[i];
}
return NULL;
}
static gcpage_t *page_metadata(void *data)
{
region_t *r = find_region(data);
assert(r);
int pg_idx = (GC_PAGE_DATA(data) - &r->pages[0][0])/GC_PAGE_SZ;
return &r->meta[pg_idx];
}
Expand Down Expand Up @@ -1747,6 +1749,33 @@ static void post_mark(arraylist_t *list, int dryrun)
visit_mark_stack(GC_MARKED_NOESC);
}

//#ifdef GC_SCRUB

char* stack_lo;
void gc_scrub(char* stack_hi)
{
char** stack_lo_a16 = (char**)((uintptr_t)stack_lo & (uintptr_t)(-16));
// printf("Stack 0x%lx - 0x%lx\n", stack_hi, stack_lo_a16);
for (uintptr_t *p = stack_lo_a16; (char*)p > stack_hi; p--) {
region_t* r;
void** o = *p;
o--; // tag
if (r = find_region(o)) {
size_t ofs = (char*)o - GC_PAGE_DATA(o);
int osize = page_metadata(o)->osize;
if (osize == 0) {
continue;
}
int obj_ofs = ofs % osize;
if (!gc_marked((char*)o - obj_ofs)) { // pointing inside an object
*p = 0xdead0000000000 | (ofs - obj_ofs);
}
}
}
}

//#endif

/*
How to debug a missing write barrier :
(or rather how I do it, if you know of a better way update this)
Expand Down Expand Up @@ -1994,11 +2023,13 @@ void prepare_sweep(void)
static void clear_mark(int);
#endif


void gc_scrub(char*);
void jl_gc_collect(int full)
{
if (!is_gc_enabled) return;
if (jl_in_gc) return;
char dummy;
char* stack_hi = &dummy;
jl_in_gc = 1;
JL_SIGATOMIC_BEGIN();
uint64_t t0 = jl_hrtime();
Expand Down Expand Up @@ -2094,7 +2125,7 @@ void jl_gc_collect(int full)
post_time = jl_hrtime() - post_time;
#endif
estimate_freed = live_bytes - scanned_bytes - perm_scanned_bytes + actual_allocd;

gc_scrub(stack_hi);
#ifdef GC_VERIFY
gc_verify();
#endif
Expand Down Expand Up @@ -2252,7 +2283,7 @@ void *reallocb(void *b, size_t sz)

DLLEXPORT jl_value_t *allocobj(size_t sz)
{
sz += sizeof(jl_taggedvalue_t);
sz += sizeof(void*);
#ifdef MEMDEBUG
return jl_valueof(alloc_big(sz));
#endif
Expand All @@ -2264,7 +2295,7 @@ DLLEXPORT jl_value_t *allocobj(size_t sz)

DLLEXPORT jl_value_t *alloc_1w(void)
{
const int sz = sizeof(jl_taggedvalue_t) + sizeof(void*);
const int sz = 2*sizeof(void*);
#ifdef MEMDEBUG
return jl_valueof(alloc_big(sz));
#endif
Expand All @@ -2273,7 +2304,7 @@ DLLEXPORT jl_value_t *alloc_1w(void)

DLLEXPORT jl_value_t *alloc_2w(void)
{
const int sz = sizeof(jl_taggedvalue_t) + sizeof(void*) * 2;
const int sz = 3*sizeof(void*);
#ifdef MEMDEBUG
return jl_valueof(alloc_big(sz));
#endif
Expand All @@ -2282,7 +2313,7 @@ DLLEXPORT jl_value_t *alloc_2w(void)

DLLEXPORT jl_value_t *alloc_3w(void)
{
const int sz = sizeof(jl_taggedvalue_t) + sizeof(void*) * 3;
const int sz = 4*sizeof(void*);
#ifdef MEMDEBUG
return jl_valueof(alloc_big(sz));
#endif
Expand Down Expand Up @@ -2332,6 +2363,7 @@ void jl_gc_init(void)
norm_pools[i].newpages = NULL;
norm_pools[i].end_offset = ((GC_PAGE_SZ/szc[i]) - 1)*szc[i];
}
stack_lo = &i;

collect_interval = default_collect_interval;
allocd_bytes = -default_collect_interval;
Expand Down
13 changes: 1 addition & 12 deletions src/julia.h
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Original file line number Diff line number Diff line change
Expand Up @@ -100,25 +100,14 @@ typedef struct {
#endif
};
};
#ifdef _P64
uintptr_t realign16;
#endif
jl_value_t value;
} jl_taggedvalue_t;

#define jl_astaggedvalue__MACRO(v) container_of((v),jl_taggedvalue_t,value)
#define jl_typeof__MACRO(v) ((jl_value_t*)(jl_astaggedvalue__MACRO(v)->type_bits&~(size_t)3))
#define jl_astaggedvalue jl_astaggedvalue__MACRO
#define jl_typeof jl_typeof__MACRO
//#define jl_set_typeof(v,t) (jl_astaggedvalue(v)->type = (jl_value_t*)(t))
static inline void jl_set_typeof(void *v, void *t)
{
jl_taggedvalue_t *tag = jl_astaggedvalue(v);
#ifdef _P64
tag->realign16 = 0xA1164A1164A11640ull;
#endif
tag->type = (jl_value_t*)t;
}
#define jl_set_typeof(v,t) (jl_astaggedvalue(v)->type = (jl_value_t*)(t))
#define jl_typeis(v,t) (jl_typeof(v)==(jl_value_t*)(t))

typedef struct _jl_sym_t {
Expand Down