debuglog_on.go

     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  //go:build debuglog
     6  
     7  package runtime
     8  
     9  const dlogEnabled = true
    10  
    11  // dlogger is the underlying implementation of the dlogger interface, selected
    12  // at build time.
    13  //
    14  // We use a type alias instead of struct embedding so that the dlogger type is
    15  // identical to the type returned by method chaining on the methods of this type.
    16  type dlogger = *dloggerImpl
    17  
    18  func dlog1() *dloggerImpl {
    19  	return dlogImpl()
    20  }
    21  
    22  // dlogPerM is the per-M debug log data. This is embedded in the m
    23  // struct.
    24  type dlogPerM struct {
    25  	dlogCache *dloggerImpl
    26  }
    27  
    28  // getCachedDlogger returns a cached dlogger if it can do so
    29  // efficiently, or nil otherwise. The returned dlogger will be owned.
    30  func getCachedDlogger() *dloggerImpl {
    31  	mp := acquirem()
    32  	// We don't return a cached dlogger if we're running on the
    33  	// signal stack in case the signal arrived while in
    34  	// get/putCachedDlogger. (Too bad we don't have non-atomic
    35  	// exchange!)
    36  	var l *dloggerImpl
    37  	if getg() != mp.gsignal {
    38  		l = mp.dlogCache
    39  		mp.dlogCache = nil
    40  	}
    41  	releasem(mp)
    42  	return l
    43  }
    44  
    45  // putCachedDlogger attempts to return l to the local cache. It
    46  // returns false if this fails.
    47  func putCachedDlogger(l *dloggerImpl) bool {
    48  	mp := acquirem()
    49  	if getg() != mp.gsignal && mp.dlogCache == nil {
    50  		mp.dlogCache = l
    51  		releasem(mp)
    52  		return true
    53  	}
    54  	releasem(mp)
    55  	return false
    56  }
    57
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