From 0b31e6d4cc804ab76ae8ced151ee2f50657aec14 Mon Sep 17 00:00:00 2001 From: Michael Pratt Date: Thu, 3 Apr 2025 03:26:25 +0000 Subject: runtime: cleanup M vgetrandom state before dropping P When an M is destroyed, we put its vgetrandom state back on the shared list for another M to reuse. This list is simply a slice, so appending to the slice may allocate. Currently this operation is performed in mdestroy, after the P is released, meaning allocation is not allowed. More the cleanup earlier in mdestroy when allocation is still OK. Also add //go:nowritebarrierrec to mdestroy since it runs without a P, which would have caught this bug. Fixes #73141. Change-Id: I6a6a636c3fbf5c6eec09d07a260e39dbb4d2db12 Reviewed-on: https://go-review.googlesource.com/c/go/+/662455 Reviewed-by: Jason Donenfeld LUCI-TryBot-Result: Go LUCI Reviewed-by: Keith Randall Reviewed-by: Keith Randall --- src/runtime/vgetrandom_linux.go | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) (limited to 'src/runtime/vgetrandom_linux.go') diff --git a/src/runtime/vgetrandom_linux.go b/src/runtime/vgetrandom_linux.go index 00ef2c2d4e..6ab12e3c67 100644 --- a/src/runtime/vgetrandom_linux.go +++ b/src/runtime/vgetrandom_linux.go @@ -74,9 +74,16 @@ func vgetrandomGetState() uintptr { return state } -func vgetrandomPutState(state uintptr) { +// Free vgetrandom state from the M (if any) prior to destroying the M. +// +// This may allocate, so it must have a P. +func vgetrandomDestroy(mp *m) { + if mp.vgetrandomState == 0 { + return + } + lock(&vgetrandomAlloc.statesLock) - vgetrandomAlloc.states = append(vgetrandomAlloc.states, state) + vgetrandomAlloc.states = append(vgetrandomAlloc.states, mp.vgetrandomState) unlock(&vgetrandomAlloc.statesLock) } -- cgit v1.3