From: Austin Clements <austin@google.com>
Date: Thu, 13 Aug 2015 03:39:10 +0000 (-0400)
Subject: runtime: fix hashing of trace stacks
X-Git-Tag: go1.6beta1~1090
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=739f13383791847fd4b0a1eab7e333b5780be039;p=gostls13.git

runtime: fix hashing of trace stacks

The call to hash the trace stack reversed the "seed" and "size"
arguments to memhash and, hence, always called memhash with a 0 size,
which dutifully returned a hash value that depended only on the number
of PCs in the stack and not their values. As a result, all stacks were
put in to a very subset of the 8,192 buckets.

Fix this by passing these arguments in the correct order.

Change-Id: I67cd29312f5615c7ffa23e205008dd72c6b8af62
Reviewed-on: https://go-review.googlesource.com/13613
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
---

diff --git a/src/runtime/trace.go b/src/runtime/trace.go
index c81846221a..29600b5c4d 100644
--- a/src/runtime/trace.go
+++ b/src/runtime/trace.go
@@ -624,7 +624,7 @@ func (tab *traceStackTable) put(pcs []uintptr) uint32 {
 	if len(pcs) == 0 {
 		return 0
 	}
-	hash := memhash(unsafe.Pointer(&pcs[0]), uintptr(len(pcs))*unsafe.Sizeof(pcs[0]), 0)
+	hash := memhash(unsafe.Pointer(&pcs[0]), 0, uintptr(len(pcs))*unsafe.Sizeof(pcs[0]))
 	// First, search the hashtable w/o the mutex.
 	if id := tab.find(pcs, hash); id != 0 {
 		return id