linux-kernel - [git pull] rcu fix

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 for Android: free password hash cracker in your pocket

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

Message-ID: <20080701195858.GA2740@elte.hu>
Date:	Tue, 1 Jul 2008 21:59:05 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [git pull] rcu fix

Linus,

Please pull the latest RCU fixes git tree from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip.git core-fixes-for-linus

Thanks,

	Ingo

------------------>
Gautham R Shenoy (1):
      rcu: fix hotplug vs rcu race

 kernel/rcuclassic.c |   16 +++++++++++++++-
 1 files changed, 15 insertions(+), 1 deletions(-)

diff --git a/kernel/rcuclassic.c b/kernel/rcuclassic.c
index f4ffbd0..a38895a 100644
--- a/kernel/rcuclassic.c
+++ b/kernel/rcuclassic.c
@@ -89,8 +89,22 @@ static void force_quiescent_state(struct rcu_data *rdp,
 		/*
 		 * Don't send IPI to itself. With irqs disabled,
 		 * rdp->cpu is the current cpu.
+		 *
+		 * cpu_online_map is updated by the _cpu_down()
+		 * using stop_machine_run(). Since we're in irqs disabled
+		 * section, stop_machine_run() is not exectuting, hence
+		 * the cpu_online_map is stable.
+		 *
+		 * However,  a cpu might have been offlined _just_ before
+		 * we disabled irqs while entering here.
+		 * And rcu subsystem might not yet have handled the CPU_DEAD
+		 * notification, leading to the offlined cpu's bit
+		 * being set in the rcp->cpumask.
+		 *
+		 * Hence cpumask = (rcp->cpumask & cpu_online_map) to prevent
+		 * sending smp_reschedule() to an offlined CPU.
 		 */
-		cpumask = rcp->cpumask;
+		cpus_and(cpumask, rcp->cpumask, cpu_online_map);
 		cpu_clear(rdp->cpu, cpumask);
 		for_each_cpu_mask(cpu, cpumask)
 			smp_send_reschedule(cpu);
--
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/