unlock(&trace.lock)
			trace.cpuBuf[gen%2] = nil
		})
	}
}

// traceCPUSample writes a CPU profile sample stack to the execution tracer's
// profiling buffer. It is called from a signal handler, so is limited in what
// it can do. mp must be the thread that is currently stopped in a signal.
func traceCPUSample(gp *g, mp *m, pp *p, stk []uintptr) {
	if !traceEnabled() {

	// until all Ms are observed to be outside of their seqlock critical section.
	//
	// Note: The seqlock is mutated here and also in traceCPUSample. If you update
	// usage of the seqlock here, make sure to also look at what traceCPUSample is
	// doing.
	seq := mp.trace.seqlock.Add(1)
	if debugTraceReentrancy && seq%2 != 1 {
		throw("bad use of trace.seqlock or tracer is reentrant")
	}

		gprof := gp
		var mp *m
		var pp *p
		if gp != nil && gp.m != nil {
			if gp.m.curg != nil {
				gprof = gp.m.curg
			}
			mp = gp.m
			pp = gp.m.p.ptr()
		}
		traceCPUSample(gprof, mp, pp, stk[:n])
	}
	getg().m.mallocing--
}

// setcpuprofilerate sets the CPU profiling rate to hz times per second.
// If hz <= 0, setcpuprofilerate turns off CPU profiling.