From a4a57bb4f9a7d4d2d7f4cbe373ab446d73c25966 Mon Sep 17 00:00:00 2001 From: Austin Clements Date: Thu, 17 Dec 2015 15:35:49 -0800 Subject: [PATCH] runtime: prevent race between setNextBarrierPC and sigprof Currently, setNextBarrierPC manipulates the stack barriers without acquiring the stack barrier lock. This is mostly okay because setNextBarrierPC also runs synchronously on the G and prevents safe points, but this doesn't prevent a sigprof from occurring during a setNextBarrierPC and performing a traceback. Given that setNextBarrierPC simply sets one entry in the stack barrier array, this is almost certainly safe in reality. However, given that this depends on a subtle argument, which may not hold in the future, and that setNextBarrierPC almost never happens, making it nowhere near performance-critical, we can simply acquire the stack barrier lock and be sure that the synchronization will work. Updates #12528. For 1.5.3. Change-Id: Ife696e10d969f190157eb1cbe762a2de2ebce079 Reviewed-on: https://go-review.googlesource.com/18022 Run-TryBot: Austin Clements Reviewed-by: Russ Cox --- src/runtime/mstkbar.go | 2 ++ 1 file changed, 2 insertions(+) diff --git a/src/runtime/mstkbar.go b/src/runtime/mstkbar.go index 6b4fc8d4a6a08..7d7235d259347 100644 --- a/src/runtime/mstkbar.go +++ b/src/runtime/mstkbar.go @@ -305,7 +305,9 @@ func nextBarrierPC() uintptr { //go:nosplit func setNextBarrierPC(pc uintptr) { gp := getg() + gcLockStackBarriers(gp) gp.stkbar[gp.stkbarPos].savedLRVal = pc + gcUnlockStackBarriers(gp) } // gcLockStackBarriers synchronizes with tracebacks of gp's stack