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Source file src/runtime/proflabel.go

Documentation: runtime

     1  // Copyright 2017 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  package runtime
     6  
     7  import "unsafe"
     8  
     9  var labelSync uintptr
    10  
    11  //go:linkname runtime_setProfLabel runtime/pprof.runtime_setProfLabel
    12  func runtime_setProfLabel(labels unsafe.Pointer) {
    13  	// Introduce race edge for read-back via profile.
    14  	// This would more properly use &getg().labels as the sync address,
    15  	// but we do the read in a signal handler and can't call the race runtime then.
    16  	//
    17  	// This uses racereleasemerge rather than just racerelease so
    18  	// the acquire in profBuf.read synchronizes with *all* prior
    19  	// setProfLabel operations, not just the most recent one. This
    20  	// is important because profBuf.read will observe different
    21  	// labels set by different setProfLabel operations on
    22  	// different goroutines, so it needs to synchronize with all
    23  	// of them (this wouldn't be an issue if we could synchronize
    24  	// on &getg().labels since we would synchronize with each
    25  	// most-recent labels write separately.)
    26  	//
    27  	// racereleasemerge is like a full read-modify-write on
    28  	// labelSync, rather than just a store-release, so it carries
    29  	// a dependency on the previous racereleasemerge, which
    30  	// ultimately carries forward to the acquire in profBuf.read.
    31  	if raceenabled {
    32  		racereleasemerge(unsafe.Pointer(&labelSync))
    33  	}
    34  	getg().labels = labels
    35  }
    36  
    37  //go:linkname runtime_getProfLabel runtime/pprof.runtime_getProfLabel
    38  func runtime_getProfLabel() unsafe.Pointer {
    39  	return getg().labels
    40  }
    41  

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