1 // Copyright 2019 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 // +build debuglog 6 7 package runtime 8 9 const dlogEnabled = true 10 11 // dlogPerM is the per-M debug log data. This is embedded in the m 12 // struct. 13 type dlogPerM struct { 14 dlogCache *dlogger 15 } 16 17 // getCachedDlogger returns a cached dlogger if it can do so 18 // efficiently, or nil otherwise. The returned dlogger will be owned. 19 func getCachedDlogger() *dlogger { 20 mp := acquirem() 21 // We don't return a cached dlogger if we're running on the 22 // signal stack in case the signal arrived while in 23 // get/putCachedDlogger. (Too bad we don't have non-atomic 24 // exchange!) 25 var l *dlogger 26 if getg() != mp.gsignal { 27 l = mp.dlogCache 28 mp.dlogCache = nil 29 } 30 releasem(mp) 31 return l 32 } 33 34 // putCachedDlogger attempts to return l to the local cache. It 35 // returns false if this fails. 36 func putCachedDlogger(l *dlogger) bool { 37 mp := acquirem() 38 if getg() != mp.gsignal && mp.dlogCache == nil { 39 mp.dlogCache = l 40 releasem(mp) 41 return true 42 } 43 releasem(mp) 44 return false 45 } 46