runtime: don't crash on mlock failure

Instead, note that mlock has failed, start trying the mitigation of
touching the signal stack before sending a preemption signal, and,
if the program crashes, mention the possible problem and a wiki page
describing the issue (https://golang.org/wiki/LinuxKernelSignalVectorBug).

Tested on a kernel in the buggy version range, but with the patch,
by using `ulimit -l 0`.

Fixes #37436

Change-Id: I072aadb2101496dffd655e442fa5c367dad46ce8
Reviewed-on: https://go-review.googlesource.com/c/go/+/223121
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Keith Randall <khr@golang.org>

1 files changed, 10 insertions, 0 deletions

diff --git a/src/runtime/panic.go b/src/runtime/panic.go
index c6ab1bac3f..28b5cbefcc 100644
--- a/src/runtime/panic.go
+++ b/src/runtime/panic.go
@@ -1281,6 +1281,12 @@ func startpanic_m() bool {
 	}
 }
 
+// throwReportQuirk, if non-nil, is called by throw after dumping the stacks.
+//
+// TODO(austin): Remove this after Go 1.15 when we remove the
+// mlockGsignal workaround.
+var throwReportQuirk func()
+
 var didothers bool
 var deadlock mutex
 
@@ -1327,6 +1333,10 @@ func dopanic_m(gp *g, pc, sp uintptr) bool {
 
 	printDebugLog()
 
+	if throwReportQuirk != nil {
+		throwReportQuirk()
+	}
+
 	return docrash
 }