From: bluhm <bluhm@openbsd.org>
Date: Wed, 22 Nov 2023 18:50:10 +0000 (+0000)
Subject: Fix race when initializing TSC.
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=9fa027f16fcb815ac6d45f93c5c75deb8f911231;p=openbsd

Fix race when initializing TSC.

During boot TSC initialization could fail with panic: tsc_test_sync_ap:
cpu2: tsc_ap_name is not NULL: cpu1.
The root cause is a race between the moment the application processor
sets CPUF_IDENTIFIED in cpu_hatch() and the moment the boot processor
checks CPUF_IDENTIFIED in cpu_start_secondary() before the TSC sync
test.
The fix is to set CPUF_IDENTIFIED before clearing CPUF_IDENTIFY in
cpu_hatch().

from hshoexer@ cheloha@; OK deraadt@ mlarkin@
---

diff --git a/sys/arch/amd64/amd64/cpu.c b/sys/arch/amd64/amd64/cpu.c
index bee2ff12b6d..db06cd7d527 100644
--- a/sys/arch/amd64/amd64/cpu.c
+++ b/sys/arch/amd64/amd64/cpu.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: cpu.c,v 1.176 2023/10/24 13:20:09 claudio Exp $	*/
+/*	$OpenBSD: cpu.c,v 1.177 2023/11/22 18:50:10 bluhm Exp $	*/
 /* $NetBSD: cpu.c,v 1.1 2003/04/26 18:39:26 fvdl Exp $ */
 
 /*-
@@ -1023,10 +1023,11 @@ cpu_hatch(void *v)
 
 		identifycpu(ci);
 
-		/* Signal we're done */
-		atomic_clearbits_int(&ci->ci_flags, CPUF_IDENTIFY);
 		/* Prevent identifycpu() from running again */
 		atomic_setbits_int(&ci->ci_flags, CPUF_IDENTIFIED);
+
+		/* Signal we're done */
+		atomic_clearbits_int(&ci->ci_flags, CPUF_IDENTIFY);
 	}
 
 	/* These have to run after identifycpu() */