jonathan-albrecht-ibm
commented
2 years ago I ran this test over the weekend with:
$ pwd
/home/jalbrecht/src/goroot/src/runtime
$ go test -timeout=0 -count=100000 -failfast -run "TestGdbPython$"and it didn't fail until the second run with count=100000 so not easily reproducible. I think its worth mentioning https://github.com/golang/go/issues/39204 for visibility.
The test output is below and contains the same traceback with the PC not saved error. Both times it looks like it happened when trying to print the backtrace for the running runtime.runfinq method.
Googling "PC not saved" turns up mostly s390x bugs reports although not a lot and no real resolution to any of the reports from what I can make of it.
I'm going to try and add some more gdb commands to see if there is any more info I can get about where in runtime.runfinq it is when this happens.
--- FAIL: TestGdbPython (0.62s) runtime-gdb_test.go:76: gdb version 8.2 runtime-gdb_test.go:265: gdb output:
Loading Go Runtime support.
Loaded Script
Yes /home/jalbrecht/src/goroot/src/runtime/runtime-gdb.py
Breakpoint 1 at 0xa65c0: file /tmp/TestGdbPython44043474/001/main.go, line 26. hi
Thread 1 "a.exe" hit Breakpoint 1, main.main () at /tmp/TestGdbPython44043474/001/main.go:26
26 gslice = slicevar
BEGIN info goroutines
* 1 running syscall.Syscall
2 waiting runtime.gopark
17 waiting runtime.gopark
18 waiting runtime.gopark
* 3 running runtime.runfinq
END
BEGIN print mapvar
$1 = map[string]string = {["abc"] = "def", ["ghi"] = "jkl"}
END
BEGIN print slicemap
$2 = map[string][]string = {["a"] = []string = {"b", "c", "d"}, ["e"] = []string = {"f", "g", "h"}}
END
BEGIN print strvar
$3 = "abc"
END
BEGIN print chanint
$4 = chan int = {99, 11} END
BEGIN print chanstr
$5 = chan string = {"spongepants", "squarebob"}
END
BEGIN info locals mapvar = map[string]string = {["abc"] = "def", ["ghi"] = "jkl"}
slicemap = map[string][]string = {["a"] = []string = {"b", "c", "d"}, ["e"] = []string = {"f", "g", "h"}} chanint = chan int = {99, 11}
chanstr = chan string = {"spongepants", "squarebob"}
ptrvar = <optimized out>
slicevar = []string
strvar = "abc"
END
BEGIN goroutine 1 bt
#0 main.main () at /tmp/TestGdbPython44043474/001/main.go:26
END
BEGIN goroutine all bt
#0 main.main () at /tmp/TestGdbPython44043474/001/main.go:26
#0 runtime.gopark (unlockf={void (runtime.g *, void *, bool *)} 0xc000038fb8, lock=0x1584a0 <runtime.forcegc>, reason=17 '\021', traceEv=20 '\024', traceskip=1) at /home/jalbrecht/src/goroot/src/runtime/proc.go:364
#1 0x000000000004ce4c in runtime.goparkunlock (lock=<optimized out>, reason=<optimized out>, traceEv=<optimized out>, traceskip=<optimized out>) at /home/jalbrecht/src/goroot/src/runtime/proc.go:369
#2 runtime.forcegchelper () at /home/jalbrecht/src/goroot/src/runtime/proc.go:302
#3 0x000000000007bec2 in runtime.goexit () at /home/jalbrecht/src/goroot/src/runtime/asm_s390x.s:742
#0 runtime.gopark (unlockf={void (runtime.g *, void *, bool *)} 0xc0000347a8, lock=0x158620 <runtime.sweep>, reason=12 '\f', traceEv=20 '\024', traceskip=1) at /home/jalbrecht/src/goroot/src/runtime/proc.go:364
#1 0x00000000000366fa in runtime.goparkunlock (lock=<optimized out>, reason=<optimized out>, traceEv=<optimized out>, traceskip=<optimized out>) at /home/jalbrecht/src/goroot/src/runtime/proc.go:369
#2 runtime.bgsweep (c=chan int) at /home/jalbrecht/src/goroot/src/runtime/mgcsweep.go:278
#3 0x0000000000029448 in runtime.gcenable.func1 () at /home/jalbrecht/src/goroot/src/runtime/mgc.go:178
#4 0x000000000007bec2 in runtime.goexit () at /home/jalbrecht/src/goroot/src/runtime/asm_s390x.s:742
#0 runtime.gopark (unlockf={void (runtime.g *, void *, bool *)} 0xc000034f88, lock=0x158660 <runtime.scavenger>, reason=13 '\r', traceEv=20 '\024', traceskip=2) at /home/jalbrecht/src/goroot/src/runtime/proc.go:364
#1 0x00000000000341fc in runtime.goparkunlock (lock=<optimized out>, reason=<optimized out>, traceEv=<optimized out>, traceskip=<optimized out>) at /home/jalbrecht/src/goroot/src/runtime/proc.go:369
#2 runtime.(*scavengerState).park (s=0x158660 <runtime.scavenger>) at /home/jalbrecht/src/goroot/src/runtime/mgcscavenge.go:389
#3 0x0000000000034884 in runtime.bgscavenge (c=chan int) at /home/jalbrecht/src/goroot/src/runtime/mgcscavenge.go:617
#4 0x00000000000293c8 in runtime.gcenable.func2 () at /home/jalbrecht/src/goroot/src/runtime/mgc.go:179
#5 0x000000000007bec2 in runtime.goexit () at /home/jalbrecht/src/goroot/src/runtime/asm_s390x.s:742
Traceback (most recent call last):
File "/home/jalbrecht/src/goroot/src/runtime/runtime-gdb.py", line 543, in invoke
self.invoke_per_goid(goid, cmd)
File "/home/jalbrecht/src/goroot/src/runtime/runtime-gdb.py", line 558, in invoke_per_goid
gdb.parse_and_eval('$pc = {0}'.format(str(pc)))
gdb.error: PC not saved
Error occurred in Python command: PC not saved
END
No breakpoint at main.go:15.
Breakpoint 2 at 0xa66f4: file /tmp/TestGdbPython44043474/001/main.go, line 29.
Thread 1 "a.exe" received signal SIGSEGV, Segmentation fault.
0x0000000000000000 in ?? ()
BEGIN goroutine 1 bt at the end
No such goroutine: 1
END
runtime-gdb_test.go:105: malformed backtrace at line 0: No such goroutine: 1
FAIL
exit status 1
FAIL runtime 1802.724s
greplogs -l -e 'gdb\.error: PC not saved'2022-06-15T17:37:53-c2c76c6/linux-s390x-ibm(attn @golang/s390x; CC @golang/runtime)