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runtime: fix map iterator concurrent map check

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We should check whether there is a concurrent writer at the
start of every mapiternext, not just in mapaccessK (which is
only called during certain map growth situations).

Tests turned off by default because they are inherently flaky.

Fixes #16278

Change-Id: I8b72cab1b8c59d1923bec6fa3eabc932e4e91542
Reviewed-on: https://go-review.googlesource.com/24749
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
This commit is contained in:
Keith Randall 2016-07-06 15:02:49 -07:00
parent a16a189fb9
commit e492d9f018
3 changed files with 117 additions and 3 deletions
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6
src/runtime/hashmap.go
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@ -382,9 +382,6 @@ func mapaccessK(t *maptype, h *hmap, key unsafe.Pointer) (unsafe.Pointer, unsafe
if h == nil || h.count == 0 {
return nil, nil
}
if h.flags&hashWriting != 0 {
throw("concurrent map read and map write")
}
alg := t.key.alg
hash := alg.hash(key, uintptr(h.hash0))
m := uintptr(1)<<h.B - 1
@ -685,6 +682,9 @@ func mapiternext(it *hiter) {
callerpc := getcallerpc(unsafe.Pointer(&it))
racereadpc(unsafe.Pointer(h), callerpc, funcPC(mapiternext))
}
if h.flags&hashWriting != 0 {
throw("concurrent map iteration and map write")
}
t := it.t
bucket := it.bucket
b := it.bptr