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Source file src/runtime/proflabel.go

Documentation: runtime

  // Copyright 2017 The Go Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style
  // license that can be found in the LICENSE file.
  
  package runtime
  
  import "unsafe"
  
  var labelSync uintptr
  
  //go:linkname runtime_setProfLabel runtime/pprof.runtime_setProfLabel
  func runtime_setProfLabel(labels unsafe.Pointer) {
  	// Introduce race edge for read-back via profile.
  	// This would more properly use &getg().labels as the sync address,
  	// but we do the read in a signal handler and can't call the race runtime then.
  	//
  	// This uses racereleasemerge rather than just racerelease so
  	// the acquire in profBuf.read synchronizes with *all* prior
  	// setProfLabel operations, not just the most recent one. This
  	// is important because profBuf.read will observe different
  	// labels set by different setProfLabel operations on
  	// different goroutines, so it needs to synchronize with all
  	// of them (this wouldn't be an issue if we could synchronize
  	// on &getg().labels since we would synchronize with each
  	// most-recent labels write separately.)
  	//
  	// racereleasemerge is like a full read-modify-write on
  	// labelSync, rather than just a store-release, so it carries
  	// a dependency on the previous racereleasemerge, which
  	// ultimately carries forward to the acquire in profBuf.read.
  	if raceenabled {
  		racereleasemerge(unsafe.Pointer(&labelSync))
  	}
  	getg().labels = labels
  }
  
  //go:linkname runtime_getProfLabel runtime/pprof.runtime_getProfLabel
  func runtime_getProfLabel() unsafe.Pointer {
  	return getg().labels
  }
  

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