suzanne.soy/racket
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

limit time for getting a native (JIT) stack trace

Browse Source 
It's possible for a deep recursion to be all in C instead of
JIT-generated code, in which case the caching code for
`current-continuation-mark' cannot kick in to make the operation
effectively constant time. Bail out (to keep things constant time) if
that happens.
This commit is contained in:
Matthew Flatt 2012-02-27 14:37:01 -07:00
parent 012ef60cd5
commit 534886dbe4
1 changed files with 18 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
src/racket/src/jitstack.c
View File

@ -70,6 +70,14 @@ typedef void *(*Get_Stack_Proc)();
#define CACHE_STACK_MIN_TRIGGER 128
/* Normally, caching of a native trace on the stack ensures that
`current-continuation-marks' is effectively constant-time.
It's possible to have a deep stack section with no recognizable anchors
for caching, however, in which case `current-continuation-marks'
can become O(n); avoid that pathological case by limiting the
number of non-anchor frames in a row that we're willing to traverse. */
#define UNKNOWN_FRAME_LIMIT 64
#define USE_STACK_CHECK 0
#if USE_STACK_CHECK
@ -134,6 +142,7 @@ Scheme_Object *scheme_native_stack_trace(void)
int use_unw = 0;
int shift_cache_to_next = 0;
int added_list_elem;
int unsuccess = 0;
if (!sjc.get_stack_pointer_code)
return NULL;
@ -180,7 +189,7 @@ Scheme_Object *scheme_native_stack_trace(void)
#endif
}
while (1) {
while (unsuccess < UNKNOWN_FRAME_LIMIT) {
#ifdef MZ_USE_DWARF_LIBUNWIND
if (use_unw) {
q = (void *)unw_get_ip(&c);
@ -270,9 +279,14 @@ Scheme_Object *scheme_native_stack_trace(void)
shift_cache_to_next = 0;
}
added_list_elem = 1;
} else
} else
added_list_elem = 0;
if (!name)
unsuccess++;
else
unsuccess = 0;
/* Cache the result halfway up the stack, if possible. Only cache
on frames where the previous frame had a return address with a
name, because an arbitrary frame's return address on the stack
@ -300,6 +314,8 @@ Scheme_Object *scheme_native_stack_trace(void)
shift_cache_to_next = 1;
halfway = stack_end;
unsuccess = -100000; /* if we got halfway, no need to bail out later */
}
prev_had_name = !!name;