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Threadsafe stack relocation

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* libguile/vm.c (vm_return_to_continuation, vm_expand_stack):
  (vm_reinstate_partial_continuation): Hold the GC lock while relocating
  the stack.
This commit is contained in:
Andy Wingo 2014-02-20 21:09:08 +01:00
parent 698c55b04b
commit c53d0f01dd
1 changed files with 131 additions and 60 deletions
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191
libguile/vm.c
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@ -132,22 +132,22 @@ scm_i_vm_capture_stack (SCM *stack_base, SCM *fp, SCM *sp, scm_t_uint32 *ra,
return scm_cell (scm_tc7_vm_cont, (scm_t_bits)p); return scm_cell (scm_tc7_vm_cont, (scm_t_bits)p);
} }
static void struct return_to_continuation_data
vm_return_to_continuation (struct scm_vm *vp, SCM cont, size_t n, SCM *argv)
{ {
struct scm_vm_cont *cp; struct scm_vm_cont *cp;
SCM *argv_copy; struct scm_vm *vp;
};
/* Called with the GC lock to prevent the stack marker from traversing a
stack in an inconsistent state. */
static void *
vm_return_to_continuation_inner (void *data_ptr)
{
struct return_to_continuation_data *data = data_ptr;
struct scm_vm *vp = data->vp;
struct scm_vm_cont *cp = data->cp;
scm_t_ptrdiff reloc; scm_t_ptrdiff reloc;
argv_copy = alloca (n * sizeof(SCM));
memcpy (argv_copy, argv, n * sizeof(SCM));
cp = SCM_VM_CONT_DATA (cont);
/* FIXME: Need to prevent GC while futzing with the stack; otherwise,
another thread causing GC may initiate a mark of a stack in an
inconsistent state. */
/* We know that there is enough space for the continuation, because we /* We know that there is enough space for the continuation, because we
captured it in the past. However there may have been an expansion captured it in the past. However there may have been an expansion
since the capture, so we may have to re-link the frame since the capture, so we may have to re-link the frame
@ -172,6 +172,25 @@ vm_return_to_continuation (struct scm_vm *vp, SCM cont, size_t n, SCM *argv)
} }
} }
return NULL;
}
static void
vm_return_to_continuation (struct scm_vm *vp, SCM cont, size_t n, SCM *argv)
{
struct scm_vm_cont *cp;
SCM *argv_copy;
struct return_to_continuation_data data;
argv_copy = alloca (n * sizeof(SCM));
memcpy (argv_copy, argv, n * sizeof(SCM));
cp = SCM_VM_CONT_DATA (cont);
data.cp = cp;
data.vp = vp;
GC_call_with_alloc_lock (vm_return_to_continuation_inner, &data);
/* Now we have the continuation properly copied over. We just need to /* Now we have the continuation properly copied over. We just need to
copy the arguments. It is not guaranteed that there is actually copy the arguments. It is not guaranteed that there is actually
space for the arguments, though, so we have to bump the SP first. */ space for the arguments, though, so we have to bump the SP first. */
@ -329,29 +348,26 @@ vm_abort (struct scm_vm *vp, SCM tag,
for (; i < nstack + tail_len; i++, tail = scm_cdr (tail)) for (; i < nstack + tail_len; i++, tail = scm_cdr (tail))
argv[i] = scm_car (tail); argv[i] = scm_car (tail);
/* FIXME: NULLSTACK (SCM_VM_DATA (vp)->sp - sp) */
vp->sp = sp; vp->sp = sp;
scm_c_abort (vp, tag, nstack + tail_len, argv, current_registers); scm_c_abort (vp, tag, nstack + tail_len, argv, current_registers);
} }
static void struct vm_reinstate_partial_continuation_data
vm_reinstate_partial_continuation (struct scm_vm *vp, SCM cont,
size_t n, SCM *argv,
scm_t_dynstack *dynstack,
scm_i_jmp_buf *registers)
{ {
struct scm_vm *vp;
struct scm_vm_cont *cp; struct scm_vm_cont *cp;
SCM *argv_copy, *base;
scm_t_ptrdiff reloc; scm_t_ptrdiff reloc;
size_t i; };
argv_copy = alloca (n * sizeof(SCM)); static void *
memcpy (argv_copy, argv, n * sizeof(SCM)); vm_reinstate_partial_continuation_inner (void *data_ptr)
{
cp = SCM_VM_CONT_DATA (cont); struct vm_reinstate_partial_continuation_data *data = data_ptr;
struct scm_vm *vp = data->vp;
vm_push_sp (vp, SCM_FRAME_LOCALS_ADDRESS (vp->fp) + cp->stack_size + n - 1); struct scm_vm_cont *cp = data->cp;
SCM *base;
scm_t_ptrdiff reloc;
base = SCM_FRAME_LOCALS_ADDRESS (vp->fp); base = SCM_FRAME_LOCALS_ADDRESS (vp->fp);
reloc = cp->reloc + (base - cp->stack_base); reloc = cp->reloc + (base - cp->stack_base);
@ -370,6 +386,35 @@ vm_reinstate_partial_continuation (struct scm_vm *vp, SCM cont,
SCM_FRAME_SET_DYNAMIC_LINK (fp, SCM_FRAME_DYNAMIC_LINK (fp) + reloc); SCM_FRAME_SET_DYNAMIC_LINK (fp, SCM_FRAME_DYNAMIC_LINK (fp) + reloc);
} }
data->reloc = reloc;
return NULL;
}
static void
vm_reinstate_partial_continuation (struct scm_vm *vp, SCM cont,
size_t n, SCM *argv,
scm_t_dynstack *dynstack,
scm_i_jmp_buf *registers)
{
struct vm_reinstate_partial_continuation_data data;
struct scm_vm_cont *cp;
SCM *argv_copy;
scm_t_ptrdiff reloc;
size_t i;
argv_copy = alloca (n * sizeof(SCM));
memcpy (argv_copy, argv, n * sizeof(SCM));
cp = SCM_VM_CONT_DATA (cont);
vm_push_sp (vp, SCM_FRAME_LOCALS_ADDRESS (vp->fp) + cp->stack_size + n - 1);
data.vp = vp;
data.cp = cp;
GC_call_with_alloc_lock (vm_reinstate_partial_continuation_inner, &data);
reloc = data.reloc;
/* Push the arguments. */ /* Push the arguments. */
for (i = 0; i < n; i++) for (i = 0; i < n; i++)
vp->sp[i + 1 - n] = argv_copy[i]; vp->sp[i + 1 - n] = argv_copy[i];
@ -985,50 +1030,76 @@ scm_i_vm_free_stack (struct scm_vm *vp)
vp->stack_size = 0; vp->stack_size = 0;
} }
struct vm_expand_stack_data
{
struct scm_vm *vp;
size_t stack_size;
SCM *new_sp;
};
static void *
vm_expand_stack_inner (void *data_ptr)
{
struct vm_expand_stack_data *data = data_ptr;
struct scm_vm *vp = data->vp;
SCM *old_stack, *new_stack;
size_t new_size;
scm_t_ptrdiff reloc;
new_size = vp->stack_size;
while (new_size < data->stack_size)
new_size *= 2;
old_stack = vp->stack_base;
new_stack = expand_stack (vp->stack_base, vp->stack_size, new_size);
if (!new_stack)
return NULL;
vp->stack_base = new_stack;
vp->stack_size = new_size;
vp->stack_limit = vp->stack_base + new_size;
reloc = vp->stack_base - old_stack;
if (reloc)
{
SCM *fp;
if (vp->fp)
vp->fp += reloc;
data->new_sp += reloc;
fp = vp->fp;
while (fp)
{
SCM *next_fp = SCM_FRAME_DYNAMIC_LINK (fp);
if (next_fp)
{
next_fp += reloc;
SCM_FRAME_SET_DYNAMIC_LINK (fp, next_fp);
}
fp = next_fp;
}
}
return new_stack;
}
static void static void
vm_expand_stack (struct scm_vm *vp, SCM *new_sp) vm_expand_stack (struct scm_vm *vp, SCM *new_sp)
{ {
scm_t_ptrdiff stack_size = new_sp + 1 - vp->stack_base; scm_t_ptrdiff stack_size = new_sp + 1 - vp->stack_base;
/* FIXME: Prevent GC while we expand the stack, to ensure that a
stack marker can trace the stack. */
if (stack_size > vp->stack_size) if (stack_size > vp->stack_size)
{ {
SCM *old_stack, *new_stack; struct vm_expand_stack_data data;
size_t new_size;
scm_t_ptrdiff reloc;
new_size = vp->stack_size; data.vp = vp;
while (new_size < stack_size) data.stack_size = stack_size;
new_size *= 2; data.new_sp = new_sp;
old_stack = vp->stack_base;
new_stack = expand_stack (vp->stack_base, vp->stack_size, new_size); if (!GC_call_with_alloc_lock (vm_expand_stack_inner, &data))
if (!new_stack)
scm_report_stack_overflow (); scm_report_stack_overflow ();
vp->stack_base = new_stack; new_sp = data.new_sp;
vp->stack_size = new_size;
vp->stack_limit = vp->stack_base + new_size;
reloc = vp->stack_base - old_stack;
if (reloc)
{
SCM *fp;
if (vp->fp)
vp->fp += reloc;
new_sp += reloc;
fp = vp->fp;
while (fp)
{
SCM *next_fp = SCM_FRAME_DYNAMIC_LINK (fp);
if (next_fp)
{
next_fp += reloc;
SCM_FRAME_SET_DYNAMIC_LINK (fp, next_fp);
}
fp = next_fp;
}
}
} }
vp->sp_max_since_gc = vp->sp = new_sp; vp->sp_max_since_gc = vp->sp = new_sp;