From c048886458ce68280ba32647a93a04902c929988 Mon Sep 17 00:00:00 2001 From: Sverker Eriksson Date: Fri, 1 Apr 2016 20:11:34 +0200 Subject: erts: Fix race for process_flag(trap_exit,true) and a concurrent exit signal. We now actually guarantee that the process will not die from exit signal *after* the call to process_flag(trap_exit,true) has returned. The race is narrow and probably quite hard to observe even if you manage to provoke it. Has only been confirmed with the help of return trace and a sleep in send_exit_signal(). Solution: Seize status lock to prevent send_exit_signal() from reading an old status (without TRAP_EXIT) and then writing PENDING_EXIT after TRAP_EXIT has been set by process_flag_2(). --- erts/emulator/beam/bif.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'erts/emulator/beam') diff --git a/erts/emulator/beam/bif.c b/erts/emulator/beam/bif.c index b43137597e..11c694233f 100644 --- a/erts/emulator/beam/bif.c +++ b/erts/emulator/beam/bif.c @@ -1566,14 +1566,17 @@ BIF_RETTYPE process_flag_2(BIF_ALIST_2) * true. For more info, see implementation of * erts_send_exit_signal(). */ + erts_smp_proc_lock(BIF_P, ERTS_PROC_LOCKS_XSIG_SEND); if (trap_exit) state = erts_smp_atomic32_read_bor_mb(&BIF_P->state, ERTS_PSFLG_TRAP_EXIT); else state = erts_smp_atomic32_read_band_mb(&BIF_P->state, ~ERTS_PSFLG_TRAP_EXIT); + erts_smp_proc_unlock(BIF_P, ERTS_PROC_LOCKS_XSIG_SEND); + #ifdef ERTS_SMP - if (ERTS_PROC_PENDING_EXIT(BIF_P)) { + if (state & ERTS_PSFLG_PENDING_EXIT) { erts_handle_pending_exit(BIF_P, ERTS_PROC_LOCK_MAIN); ERTS_BIF_EXITED(BIF_P); } -- cgit v1.2.3