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Fix race condition between 'abort-to-prompt' and stack marking.

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Fixes <https://bugs.gnu.org/28211>.

* libguile/vm.c (scm_i_vm_emergency_abort, abort_to_prompt): Move
'vp->fp' assignment above 'sp[nargs]' assignments.
This commit is contained in:
Ludovic Courtès 2020-03-17 22:51:40 +01:00
parent 5d715dd467
commit 89edd1bc2d
1 changed files with 10 additions and 2 deletions
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12
libguile/vm.c
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@ -1385,6 +1385,11 @@ scm_i_vm_emergency_abort (SCM *tag_and_argv, size_t n)
fp = vp->stack_top - fp_offset; fp = vp->stack_top - fp_offset;
sp = vp->stack_top - sp_offset; sp = vp->stack_top - sp_offset;
/* Restore FP first so that a concurrent 'scm_i_vm_mark_stack' does
not overwrite the 'abort' arguments assigned below (see
<https://bugs.gnu.org/28211>). */
vp->fp = fp;
/* Continuation gets nargs+1 values: the one more is for the cont. */ /* Continuation gets nargs+1 values: the one more is for the cont. */
sp = sp - nargs - 1; sp = sp - nargs - 1;
@ -1398,7 +1403,6 @@ scm_i_vm_emergency_abort (SCM *tag_and_argv, size_t n)
sp[nargs].as_scm = *argv++; sp[nargs].as_scm = *argv++;
/* Restore VM regs */ /* Restore VM regs */
vp->fp = fp;
vp->sp = sp; vp->sp = sp;
vp->ip = vra; vp->ip = vra;
@ -1456,6 +1460,11 @@ abort_to_prompt (scm_thread *thread, uint8_t *saved_mra)
/* Continuation gets nargs+1 values: the one more is for the cont. */ /* Continuation gets nargs+1 values: the one more is for the cont. */
sp = sp - nargs - 1; sp = sp - nargs - 1;
/* Restore FP first so that a concurrent 'scm_i_vm_mark_stack' does
not overwrite the 'abort' arguments assigned below (see
<https://bugs.gnu.org/28211>). */
vp->fp = fp;
/* Shuffle abort arguments down to the prompt continuation. We have /* Shuffle abort arguments down to the prompt continuation. We have
to be jumping to an older part of the stack. */ to be jumping to an older part of the stack. */
if (sp < vp->sp) if (sp < vp->sp)
@ -1465,7 +1474,6 @@ abort_to_prompt (scm_thread *thread, uint8_t *saved_mra)
sp[nargs] = vp->sp[nargs]; sp[nargs] = vp->sp[nargs];
/* Restore VM regs */ /* Restore VM regs */
vp->fp = fp;
vp->sp = sp; vp->sp = sp;
vp->ip = vra; vp->ip = vra;