Fix sff panic deadlock, share the evdev probe, assorted review cleanups

system.go

@@ -100,7 +100,7 @@ func allRuleLocations(fd int, ifname string) ([]uint32, uint32, error) {
 	// rule_locs follows rule_cnt directly, before the struct's tail padding,
 	// and that is where the kernel copies it to.
 	locOff := unsafe.Offsetof(ethtoolRxnfc{}.ruleCnt) + 4
-	buf := make([]byte, int(unsafe.Sizeof(ethtoolRxnfc{}))+4*int(cnt.ruleCnt))
+	buf := statsBuf((int(unsafe.Sizeof(ethtoolRxnfc{})) + 4*int(cnt.ruleCnt) + 7) / 8)
 	all := (*ethtoolRxnfc)(unsafe.Pointer(&buf[0]))
 	all.cmd = ethtoolGRXCLSRLALL
 	all.ruleCnt = cnt.ruleCnt
@@ -113,7 +113,7 @@ func allRuleLocations(fd int, ifname string) ([]uint32, uint32, error) {
 			ifname, all.ruleCnt, cnt.ruleCnt)
 	}
 
-	raw := buf[locOff:]
+	raw := unsafe.Slice((*byte)(unsafe.Pointer(&buf[0])), len(buf)*8)[locOff:]
 	locs := make([]uint32, 0, all.ruleCnt)
 	for i := 0; i < int(all.ruleCnt); i++ {
 		locs = append(locs, binary.LittleEndian.Uint32(raw[i*4:]))
@@ -311,7 +311,10 @@ type ethtoolCoalesce struct {
 }
 
 const (
-	wantGovernor      = "performance"
+	wantGovernor = "performance"
+	// Under the performance governor a max-frequency bound is a fixed clock, not a
+	// ceiling the cores rove beneath, so the line-rate margin it was qualified with
+	// is the margin every run gets.
 	wantMaxFreqKHz    = "2000000"
 	wantCoalesceUsecs = 25
 	wantRxRing        = 8160
@@ -522,11 +525,11 @@ func (r *statReader) sum() uint64 {
 	return total
 }
 
-func checkGovernor(want string) checkResult {
-	res := checkResult{item: "cpu governor"}
-	paths, err := filepath.Glob("/sys/devices/system/cpu/cpu*/cpufreq/scaling_governor")
+func checkCPUAttr(item, attr, want, unit string) checkResult {
+	res := checkResult{item: item}
+	paths, err := filepath.Glob("/sys/devices/system/cpu/cpu*/cpufreq/" + attr)
 	if err != nil || len(paths) == 0 {
-		res.err = fmt.Errorf("no cpufreq governors found")
+		res.err = fmt.Errorf("no cpufreq %s found", attr)
 		return res
 	}
 	var wrong []string
@@ -544,7 +547,7 @@ func checkGovernor(want string) checkResult {
 		}
 	}
 	if len(wrong) == 0 {
-		res.state = fmt.Sprintf("%s on all %d cpus", want, len(paths))
+		res.state = fmt.Sprintf("%s%s on all %d cpus", want, unit, len(paths))
 		return res
 	}
 	var found []string
@@ -559,51 +562,7 @@ func checkGovernor(want string) checkResult {
 		}
 	}
 	res.fixed = true
-	res.state = fmt.Sprintf("was %s, now %s on all %d cpus", strings.Join(found, " "), want, len(paths))
-	return res
-}
-
-// Under the performance governor a max-frequency bound is a fixed clock, not a
-// ceiling the cores rove beneath, so the line-rate margin it was qualified with
-// is the margin every run gets.
-func checkMaxFreq(wantKHz string) checkResult {
-	res := checkResult{item: "cpu max frequency"}
-	paths, err := filepath.Glob("/sys/devices/system/cpu/cpu*/cpufreq/scaling_max_freq")
-	if err != nil || len(paths) == 0 {
-		res.err = fmt.Errorf("no cpufreq max frequencies found")
-		return res
-	}
-	var wrong []string
-	counts := map[string]int{}
-	for _, p := range paths {
-		b, err := os.ReadFile(p)
-		if err != nil {
-			res.err = err
-			return res
-		}
-		got := strings.TrimSpace(string(b))
-		counts[got]++
-		if got != wantKHz {
-			wrong = append(wrong, p)
-		}
-	}
-	if len(wrong) == 0 {
-		res.state = fmt.Sprintf("%s kHz on all %d cpus", wantKHz, len(paths))
-		return res
-	}
-	var found []string
-	for k, v := range counts {
-		found = append(found, fmt.Sprintf("%s:%d", k, v))
-	}
-	for _, p := range wrong {
-		if err := os.WriteFile(p, []byte(wantKHz), 0o644); err != nil {
-			res.err = err
-			res.state = fmt.Sprintf("could not set %s", p)
-			return res
-		}
-	}
-	res.fixed = true
-	res.state = fmt.Sprintf("was %s, now %s kHz on all %d cpus", strings.Join(found, " "), wantKHz, len(paths))
+	res.state = fmt.Sprintf("was %s, now %s%s on all %d cpus", strings.Join(found, " "), want, unit, len(paths))
 	return res
 }
 
@@ -774,7 +733,9 @@ func withIoctlSocket(fn func(fd int) []checkResult) []checkResult {
 // under test, so with no cable there is never going to be one.
 func configureSystem(ifnames []string, ethertypes []uint16) []checkResult {
 	return withIoctlSocket(func(fd int) []checkResult {
-		out := []checkResult{checkGovernor(wantGovernor), checkMaxFreq(wantMaxFreqKHz),
+		out := []checkResult{
+			checkCPUAttr("cpu governor", "scaling_governor", wantGovernor, ""),
+			checkCPUAttr("cpu max frequency", "scaling_max_freq", wantMaxFreqKHz, " kHz"),
 			checkIdleLatency(wantIdleLatency)}
 		for i, ifname := range ifnames {
 			out = append(out, checkLinkUp(fd, ifname))