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fix bug: "bthread switch" result in "sched_to itself!" #1313

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fix bug: "bthread switch" result in "sched_to itself!" #1313

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13 changes: 12 additions & 1 deletion src/bthread/task_group.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -318,8 +318,16 @@ void TaskGroup::task_runner(intptr_t skip_remained) {
KeyTable* kt = tls_bls.keytable;
if (kt != NULL) {
return_keytable(m->attr.keytable_pool, kt);
// return_keytable(m->attr.keytable_pool, kt); ---> delete kt; ---> delete _subs[i]; --> ~KeyTable()
// --> _subs[i]->clear(i * KEY_2NDLEVEL_SIZE); ---> info.dtor(p, info.dtor_args);
// inside info.dtor function, group is probably changed (bthread change)
g = tls_task_group; // must need

// After deletion: tls may be set during deletion.
tls_bls.keytable = NULL;
// tls_bls.keytable = NULL;
// if set tls_bls.keytable null before return_keytable, bthread change may continue use tls_bls.keytable in return_keytable;
// if set tls_bls.keytable null after return_keytable, tls_bls may change after return_keytable, and modifying data across threads is dangerous;
// since get next_meta will reset tls_bls(cur_meta/_main_meta --> next_meta), just not set.
m->local_storage.keytable = NULL; // optional
}

Expand Down Expand Up @@ -586,6 +594,9 @@ void TaskGroup::sched_to(TaskGroup** pg, TaskMeta* next_meta) {
++ g->_nswitch;
// Switch to the task
if (__builtin_expect(next_meta != cur_meta, 1)) {
if(g != tls_task_group) // check
{ abort(); }

g->_cur_meta = next_meta;
// Switch tls_bls
cur_meta->local_storage = tls_bls;
Expand Down