BT
/F42 8.9664 Tf 65.9552 712.0299 Td[(When)-356(a)-355(trace)-356(call)-356(returns,)-356(the)-355(monitor)-356(restores)-356(the)-355(interpreter)]TJ -11.9552 -9.9627 Td[(state.)-391(First,)-390(the)-391(monitor)-391(checks)-390(the)-391(reason)-391(for)-391(the)-390(trace)-391(e)15(xit)-391(and)]TJ 0 -9.9626 Td[(applies)-354(blacklisting)-355(if)-354(needed.)-355(Then,)-354(it)-354(pops)-355(or)-354(synthesizes)-355(inter)20(-)]TJ 0 -9.9626 Td[(preter)-273(Ja)20(v)25(aScript)-272(call)-273(stack)-273(frames)-272(as)-273(needed.)-273(Finally)65(,)-272(it)-273(copies)-273(the)]TJ 0 -9.9627 Td[(imported)-291(v)25(ariables)-292(back)-291(from)-292(the)-291(trace)-292(acti)25(v)25(ation)-291(record)-292(to)-291(the)-292(in-)]TJ 0 -9.9626 Td[(terpreter)-250(state.)]TJ 11.9552 -9.9627 Td[(At)-296(least)-295(in)-296(the)-295(current)-296(implementation,)-295(these)-296(steps)-295(ha)20(v)15(e)-296(a)-295(non-)]TJ -11.9552 -9.9626 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Td[(6.4)-1000(Pr)18(eemption)]TJ/F42 8.9664 Tf 0 -13.9477 Td[(SpiderMonk)10(e)15(y)65(,)-223(lik)10(e)-223(man)15(y)-223(VMs,)-223(needs)-223(to)-223(preempt)-224(the)-223(user)-223(program)]TJ 0 -9.9626 Td[(periodically)65(.)-441(The)-440(main)-441(reasons)-440(are)-441(to)-441(pre)25(v)15(ent)-440(in\002nitely)-441(looping)]TJ 0 -9.9626 Td[(scripts)-250(from)-250(locking)-250(up)-250(the)-250(host)-250(system)-250(and)-250(to)-250(schedule)-250(GC.)]TJ 11.9552 -9.9627 Td[(In)-274(the)-274(interpreter)40(,)-274(this)-274(had)-274(been)-274(implemented)-274(by)-273(setting)-274(a)-274(\223pre-)]TJ -11.9552 -9.9626 Td[(empt)-357(no)25(w\224)-358(\003ag)-357(that)-357(w)10(as)-357(check)10(ed)-358(on)-357(e)25(v)15(ery)-357(backw)10(ard)-357(jump.)-358(This)]TJ 0 -9.9627 Td[(strate)15(gy)-244(carried)-245(o)15(v)15(er)-244(into)-245(T)35(raceMonk)10(e)15(y:)-244(the)-245(VM)-244(inserts)-245(a)-244(guard)-245(on)]TJ 0 -9.9626 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ET