log: m unset ticking flag on timer end

with defer, the flag is unset only when periodicFlush fn returns,
which may be too late, as the timer has already stopped and so,
the flag must be unset right away and not after any more delays.

Author: ignoramous

intra/log/memconsole.go

@@ -49,9 +49,9 @@ const waitPeriodOnFull = 3 * time.Millisecond
 // memBufSize is the total region passed to Ftruncate/Mmap.
 var (
 	nofpages    = 16
-	memSlotSize = charsPerLine                                          // 800 bytes per slot
-	memNumSlots = nofpages * unix.Getpagesize()/memSlotSize // slots that fit in one page
-	memBufSize  = memHdrSize + memNumSlots*memSlotSize                  // ~1 page
+	memSlotSize = charsPerLine                                // 800 bytes per slot
+	memNumSlots = nofpages * unix.Getpagesize() / memSlotSize // slots that fit in one page
+	memBufSize  = memHdrSize + memNumSlots*memSlotSize        // ~1 page
 )
 
 // mcbuf is a fixed-slot shared-memory region backed by a memfd.
@@ -288,10 +288,10 @@ rollover:
 // ticker is a one-shot timer goroutine started by the first-write after each
 // buffer reset. It fires once after memFlushInterval and calls periodicFlush.
 func (mc *Memconsole) ticker() {
-	defer mc.ticking.Store(false)
 	t := time.NewTimer(memFlushInterval)
 	defer t.Stop()
 	<-t.C
+	mc.ticking.Store(false) // TODO: may be racy; mutex it?
 	mc.periodicFlush()
 }