From 8dd7d2111b8622dac4b0127fa1d26da3c1c4c274 Mon Sep 17 00:00:00 2001 From: Michael Pratt Date: Tue, 27 May 2025 10:37:50 -0400 Subject: [PATCH] runtime: skip nil Ps in allp during cleanup flush cleanupQueue.Flush is reachable from mallocgc via sweepAssist. Normally allp will continue all valid Ps, but procresize itself increases the size of allp and then allocates new Ps to place in allp. If we get perfectly unlucky, the new(p) allocations will complete sweeping and cleanupQueue.Flush will dereference a nil pointer from allp. Avoid this by skipping nil Ps. I've looked through every other use of allp and none of them appear to be reachable from procresize. Change-Id: I6a6a636cab49ef268eb8fcd9ff9a96790d9c5685 Reviewed-on: https://go-review.googlesource.com/c/go/+/676515 Auto-Submit: Michael Pratt Reviewed-by: Carlos Amedee LUCI-TryBot-Result: Go LUCI Reviewed-by: Michael Knyszek --- src/runtime/mcleanup.go | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/src/runtime/mcleanup.go b/src/runtime/mcleanup.go index 5cbae156ba..c368730c57 100644 --- a/src/runtime/mcleanup.go +++ b/src/runtime/mcleanup.go @@ -457,6 +457,13 @@ func (q *cleanupQueue) flush() { // new cleanup goroutines. var cb *cleanupBlock for _, pp := range allp { + if pp == nil { + // This function is reachable via mallocgc in the + // middle of procresize, when allp has been resized, + // but the new Ps not allocated yet. + missing++ + continue + } b := pp.cleanups if b == nil { missing++ -- 2.51.0