From e19d6e4463a9cc3b738fd32a46e0ce9282a70fd5 Mon Sep 17 00:00:00 2001 From: Rickard Green Date: Fri, 22 Jan 2010 13:47:23 +0000 Subject: OTP-8386 Immediately repeated multi-scheduling block/unblock cycles using erlang:system_flag(multi_scheduling, block | unblock) could deadlock the runtime system. --- erts/emulator/beam/erl_process.c | 22 +++++++++++++--------- 1 file changed, 13 insertions(+), 9 deletions(-) (limited to 'erts/emulator/beam') diff --git a/erts/emulator/beam/erl_process.c b/erts/emulator/beam/erl_process.c index 476e29d96f..b519b39d63 100644 --- a/erts/emulator/beam/erl_process.c +++ b/erts/emulator/beam/erl_process.c @@ -2522,8 +2522,11 @@ suspend_scheduler(ErtsSchedulerData *esdp) NULL); } - erts_smp_atomic_inc(&schdlr_sspnd.active); - + active_schedulers = erts_smp_atomic_inctest(&schdlr_sspnd.active); + if (schdlr_sspnd.changing == ERTS_SCHED_CHANGING_MULTI_SCHED + && schdlr_sspnd.online == active_schedulers) { + schdlr_sspnd.changing = 0; + } erts_smp_mtx_unlock(&schdlr_sspnd.mtx); if (erts_system_profile_flags.scheduler) @@ -2750,11 +2753,12 @@ erts_block_multi_scheduling(Process *p, ErtsProcLocks plocks, int on, int all) ErtsProcList *plp; erts_smp_mtx_lock(&schdlr_sspnd.mtx); - if (on) { - if (schdlr_sspnd.changing) { - res = ERTS_SCHDLR_SSPND_YIELD_RESTART; /* Yield */ - } - else if (erts_is_multi_scheduling_blocked()) { + + if (schdlr_sspnd.changing) { + res = ERTS_SCHDLR_SSPND_YIELD_RESTART; /* Yield */ + } + else if (on) { /* ------ BLOCK ------ */ + if (erts_is_multi_scheduling_blocked()) { plp = proclist_create(p); plp->next = schdlr_sspnd.msb.procs; schdlr_sspnd.msb.procs = plp; @@ -2842,10 +2846,11 @@ erts_block_multi_scheduling(Process *p, ErtsProcLocks plocks, int on, int all) } } else if (!ongoing_multi_scheduling_block()) { + /* unblock not ongoing */ ASSERT(!schdlr_sspnd.msb.procs); res = ERTS_SCHDLR_SSPND_DONE; } - else { + else { /* ------ UNBLOCK ------ */ if (p->flags & F_HAVE_BLCKD_MSCHED) { ErtsProcList **plpp = &schdlr_sspnd.msb.procs; plp = schdlr_sspnd.msb.procs; @@ -2930,7 +2935,6 @@ erts_block_multi_scheduling(Process *p, ErtsProcLocks plocks, int on, int all) erts_smp_mtx_lock(&schdlr_sspnd.mtx); } erts_smp_cnd_broadcast(&schdlr_sspnd.cnd); - schdlr_sspnd.changing = 0; res = ERTS_SCHDLR_SSPND_DONE; } } -- cgit v1.2.3