From c9321f3fb13aec7af5c72d3d11a6e3b4d88dced3 Mon Sep 17 00:00:00 2001 From: Dmitry Vyukov Date: Thu, 29 Jan 2015 12:47:30 +0300 Subject: [PATCH] runtime: fix nosplit stack overflow The overflow happens only with -gcflags="-N -l" and can be reproduced with: $ go test -gcflags="-N -l" -a -run=none net runtime.cgocall: nosplit stack overflow 504 assumed on entry to runtime.cgocall 480 after runtime.cgocall uses 24 472 on entry to runtime.cgocall_errno 408 after runtime.cgocall_errno uses 64 400 on entry to runtime.exitsyscall 288 after runtime.exitsyscall uses 112 280 on entry to runtime.exitsyscallfast 152 after runtime.exitsyscallfast uses 128 144 on entry to runtime.writebarrierptr 88 after runtime.writebarrierptr uses 56 80 on entry to runtime.writebarrierptr_nostore1 24 after runtime.writebarrierptr_nostore1 uses 56 16 on entry to runtime.acquirem -24 after runtime.acquirem uses 40 Move closure creation into separate function so that frames of writebarrierptr_shadow and writebarrierptr_nostore1 are overlapped. Fixes #9721 Change-Id: I40851f0786763ee964af34814edbc3e3d73cf4e7 Reviewed-on: https://go-review.googlesource.com/3418 Reviewed-by: Russ Cox --- src/runtime/mbarrier.go | 37 +++++++++++++++++++++---------------- 1 file changed, 21 insertions(+), 16 deletions(-) diff --git a/src/runtime/mbarrier.go b/src/runtime/mbarrier.go index c9ed035dab..33d67c4976 100644 --- a/src/runtime/mbarrier.go +++ b/src/runtime/mbarrier.go @@ -110,28 +110,33 @@ func writebarrierptr(dst *uintptr, src uintptr) { } if mheap_.shadow_enabled { - systemstack(func() { - addr := uintptr(unsafe.Pointer(dst)) - shadow := shadowptr(addr) - if shadow == nil { - return - } - // There is a race here but only if the program is using - // racy writes instead of sync/atomic. In that case we - // don't mind crashing. - if *shadow != *dst && *shadow != noShadow && istrackedptr(*dst) { - mheap_.shadow_enabled = false - print("runtime: write barrier dst=", dst, " old=", hex(*dst), " shadow=", shadow, " old=", hex(*shadow), " new=", hex(src), "\n") - throw("missed write barrier") - } - *shadow = src - }) + writebarrierptr_shadow(dst, src) } *dst = src writebarrierptr_nostore1(dst, src) } +//go:nosplit +func writebarrierptr_shadow(dst *uintptr, src uintptr) { + systemstack(func() { + addr := uintptr(unsafe.Pointer(dst)) + shadow := shadowptr(addr) + if shadow == nil { + return + } + // There is a race here but only if the program is using + // racy writes instead of sync/atomic. In that case we + // don't mind crashing. + if *shadow != *dst && *shadow != noShadow && istrackedptr(*dst) { + mheap_.shadow_enabled = false + print("runtime: write barrier dst=", dst, " old=", hex(*dst), " shadow=", shadow, " old=", hex(*shadow), " new=", hex(src), "\n") + throw("missed write barrier") + } + *shadow = src + }) +} + // Like writebarrierptr, but the store has already been applied. // Do not reapply. //go:nosplit -- 2.50.0