[PATCH v2 15/45] rcu: Use get/put_online_cpus_atomic() to prevent CPU offline
From: Srivatsa S. Bhat <hidden>
Date: 2013-06-25 20:31:32
Also in:
linux-pm, linuxppc-dev, lkml, netdev
Subsystem:
the rest · Maintainer:
Linus Torvalds
Once stop_machine() is gone from the CPU offline path, we won't be able to depend on disabling preemption to prevent CPUs from going offline from under us. In RCU code, rcu_implicit_dynticks_qs() checks if a CPU is offline, while being protected by a spinlock. Use the get/put_online_cpus_atomic() APIs to prevent CPUs from going offline, while invoking from atomic context. Cc: Dipankar Sarma <redacted> Cc: "Paul E. McKenney" <redacted> Signed-off-by: Srivatsa S. Bhat <redacted> --- kernel/rcutree.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index cf3adc6..caeed1a 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c@@ -2107,6 +2107,8 @@ static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *)) rcu_initiate_boost(rnp, flags); /* releases rnp->lock */ continue; } + + get_online_cpus_atomic(); cpu = rnp->grplo; bit = 1; for (; cpu <= rnp->grphi; cpu++, bit <<= 1) {
@@ -2114,6 +2116,8 @@ static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *)) f(per_cpu_ptr(rsp->rda, cpu))) mask |= bit; } + put_online_cpus_atomic(); + if (mask != 0) { /* rcu_report_qs_rnp() releases rnp->lock. */