linux-kernel - [S390] etr: Add barrier() to etr_sync_cpu

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Date:	Wed, 21 Feb 2007 11:01:42 +0100
From:	Martin Schwidefsky <schwidefsky@...ibm.com>
To:	linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org
Cc:	heiko.carstens@...ibm.com
Subject: [S390] etr: Add barrier() to etr_sync_cpu_start().

From: Heiko Carstens <heiko.carstens@...ibm.com>

[S390] etr: Add barrier() to etr_sync_cpu_start().

Force reading of *in_sync in while loop. Loops where the content that
is checked for is changed by a different cpu always should have some
sort of barrier() semantics.
Otherwise this might lead to very subtle bugs.

Signed-off-by: Heiko Carstens <heiko.carstens@...ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@...ibm.com>
---

 arch/s390/kernel/time.c |   10 +++++++++-
 1 files changed, 9 insertions(+), 1 deletion(-)

diff -urpN linux-2.6/arch/s390/kernel/time.c linux-2.6-patched/arch/s390/kernel/time.c
--- linux-2.6/arch/s390/kernel/time.c	2007-02-21 10:47:06.000000000 +0100
+++ linux-2.6-patched/arch/s390/kernel/time.c	2007-02-21 10:47:28.000000000 +0100
@@ -747,6 +747,7 @@ static void etr_adjust_time(unsigned lon
 	}
 }
 
+#ifdef CONFIG_SMP
 static void etr_sync_cpu_start(void *dummy)
 {
 	int *in_sync = dummy;
@@ -758,8 +759,14 @@ static void etr_sync_cpu_start(void *dum
 	 * __udelay will stop the cpu on an enabled wait psw until the
 	 * TOD is running again.
 	 */
-	while (*in_sync == 0)
+	while (*in_sync == 0) {
 		__udelay(1);
+		/*
+		 * A different cpu changes *in_sync. Therefore use
+		 * barrier() to force memory access.
+		 */
+		barrier();
+	}
 	if (*in_sync != 1)
 		/* Didn't work. Clear per-cpu in sync bit again. */
 		etr_disable_sync_clock(NULL);
@@ -773,6 +780,7 @@ static void etr_sync_cpu_start(void *dum
 static void etr_sync_cpu_end(void *dummy)
 {
 }
+#endif /* CONFIG_SMP */
 
 /*
  * Sync the TOD clock using the port refered to by aibp. This port
-- 
blue skies,              IBM Deutschland Entwicklung GmbH
   Martin                Vorsitzender des Aufsichtsrats: Johann Weihen
                         Geschäftsführung: Herbert Kircher 
Martin Schwidefsky       Sitz der Gesellschaft: Böblingen
Linux on zSeries         Registergericht: Amtsgericht Stuttgart,
   Development           HRB 243294
   
"Reality continues to ruin my life." - Calvin.

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/