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threading: fix race condition in pop_signal

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The pending interrupts list may be modified after we have checked
    whether it is nil, but before we aquire the spinlock, leading to
    segmentation faults.
This commit is contained in:
Marius Gerbershagen 2018-02-18 21:03:07 +01:00
parent 24e4c13d58
commit 7d6112d0e8
1 changed files with 11 additions and 10 deletions
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21
src/c/unixint.d
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@ -422,17 +422,18 @@ static cl_object
pop_signal(cl_env_ptr env)
{
cl_object record, value;
if (env->interrupt_struct->pending_interrupt == ECL_NIL) {
return ECL_NIL;
}
ECL_WITH_SPINLOCK_BEGIN(env, &env->interrupt_struct->signal_queue_spinlock) {
record = env->interrupt_struct->pending_interrupt;
value = ECL_CONS_CAR(record);
env->interrupt_struct->pending_interrupt = ECL_CONS_CDR(record);
/* Save some conses for future use, to avoid allocating */
if (ECL_SYMBOLP(value) || ECL_FIXNUMP(value)) {
ECL_RPLACD(record, env->interrupt_struct->signal_queue);
env->interrupt_struct->signal_queue = record;
if (env->interrupt_struct->pending_interrupt == ECL_NIL) {
value = ECL_NIL;
} else {
record = env->interrupt_struct->pending_interrupt;
value = ECL_CONS_CAR(record);
env->interrupt_struct->pending_interrupt = ECL_CONS_CDR(record);
/* Save some conses for future use, to avoid allocating */
if (ECL_SYMBOLP(value) || ECL_FIXNUMP(value)) {
ECL_RPLACD(record, env->interrupt_struct->signal_queue);
env->interrupt_struct->signal_queue = record;
}
}
} ECL_WITH_SPINLOCK_END;
return value;