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      1 // +build !nacl,disabled_see_issue_18589
      2 // buildrun -t 10  -gcflags=-d=ssa/insert_resched_checks/on,ssa/check/on
      3 
      4 // Copyright 2016 The Go Authors. All rights reserved.
      5 // Use of this source code is governed by a BSD-style
      6 // license that can be found in the LICENSE file.
      7 
      8 // Test is disabled because it flakes when run in all.bash
      9 // on some platforms, but is useful standalone to verify
     10 // that rescheduling checks are working (and we may wish
     11 // to investigate the flake, since it suggests that the
     12 // loop rescheduling check may not work right on those
     13 // platforms).
     14 
     15 // This checks to see that call-free infinite loops do not
     16 // block garbage collection.  IF YOU RUN IT STANDALONE without
     17 // -gcflags=-d=ssa/insert_resched_checks/on in a not-experimental
     18 // build, it should hang.
     19 
     20 package main
     21 
     22 import (
     23 	"runtime"
     24 )
     25 
     26 var someglobal1 int
     27 var someglobal2 int
     28 var someglobal3 int
     29 
     30 //go:noinline
     31 func f() {}
     32 
     33 func standinacorner1() {
     34 	for someglobal1&1 == 0 {
     35 		someglobal1++
     36 		someglobal1++
     37 	}
     38 }
     39 
     40 func standinacorner2(i int) {
     41 	// contains an irreducible loop containing changes to memory
     42 	if i != 0 {
     43 		goto midloop
     44 	}
     45 
     46 loop:
     47 	if someglobal2&1 != 0 {
     48 		goto done
     49 	}
     50 	someglobal2++
     51 midloop:
     52 	someglobal2++
     53 	goto loop
     54 
     55 done:
     56 	return
     57 }
     58 
     59 func standinacorner3() {
     60 	for someglobal3&1 == 0 {
     61 		if someglobal3&2 != 0 {
     62 			for someglobal3&3 == 2 {
     63 				someglobal3++
     64 				someglobal3++
     65 				someglobal3++
     66 				someglobal3++
     67 			}
     68 		}
     69 		someglobal3++
     70 		someglobal3++
     71 		someglobal3++
     72 		someglobal3++
     73 	}
     74 }
     75 
     76 func main() {
     77 	go standinacorner1()
     78 	go standinacorner2(0)
     79 	go standinacorner3()
     80 	// println("About to stand in a corner1")
     81 	for someglobal1 == 0 {
     82 		runtime.Gosched()
     83 	}
     84 	// println("About to stand in a corner2")
     85 	for someglobal2 == 0 {
     86 		runtime.Gosched()
     87 	}
     88 	// println("About to stand in a corner3")
     89 	for someglobal3 == 0 {
     90 		runtime.Gosched()
     91 	}
     92 	// println("About to GC")
     93 	runtime.GC()
     94 	// println("Success")
     95 }
     96