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| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2008-01-25 21:08:24 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2008-01-25 21:08:24 +0100 |
| commit | e0ecfa7917cafe72f4a75f87e8bb5d8d51dc534f (patch) | |
| tree | 92106dbd88530d3884bc6c4d1c088cba1ad8630e | |
| parent | 01c1c660f4b8086cad7a62345fd04290f3d82c8f (diff) | |
| download | lwn-e0ecfa7917cafe72f4a75f87e8bb5d8d51dc534f.tar.gz lwn-e0ecfa7917cafe72f4a75f87e8bb5d8d51dc534f.zip | |
Preempt-RCU: fix rcu_barrier for preemptive environment.
Fix rcu_barrier() to work properly in preemptive kernel environment.
Also, the ordering of callback must be preserved while moving
callbacks to another CPU during CPU hotplug.
Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
| -rw-r--r-- | kernel/rcuclassic.c | 2 | ||||
| -rw-r--r-- | kernel/rcupdate.c | 10 |
2 files changed, 11 insertions, 1 deletions
diff --git a/kernel/rcuclassic.c b/kernel/rcuclassic.c index 18369e3386e2..ce0cf16cab67 100644 --- a/kernel/rcuclassic.c +++ b/kernel/rcuclassic.c @@ -371,9 +371,9 @@ static void __rcu_offline_cpu(struct rcu_data *this_rdp, if (rcp->cur != rcp->completed) cpu_quiet(rdp->cpu, rcp); spin_unlock_bh(&rcp->lock); + rcu_move_batch(this_rdp, rdp->donelist, rdp->donetail); rcu_move_batch(this_rdp, rdp->curlist, rdp->curtail); rcu_move_batch(this_rdp, rdp->nxtlist, rdp->nxttail); - rcu_move_batch(this_rdp, rdp->donelist, rdp->donetail); } static void rcu_offline_cpu(int cpu) diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c index 0ccd0095ebdc..760dfc233a00 100644 --- a/kernel/rcupdate.c +++ b/kernel/rcupdate.c @@ -115,7 +115,17 @@ void rcu_barrier(void) mutex_lock(&rcu_barrier_mutex); init_completion(&rcu_barrier_completion); atomic_set(&rcu_barrier_cpu_count, 0); + /* + * The queueing of callbacks in all CPUs must be atomic with + * respect to RCU, otherwise one CPU may queue a callback, + * wait for a grace period, decrement barrier count and call + * complete(), while other CPUs have not yet queued anything. + * So, we need to make sure that grace periods cannot complete + * until all the callbacks are queued. + */ + rcu_read_lock(); on_each_cpu(rcu_barrier_func, NULL, 0, 1); + rcu_read_unlock(); wait_for_completion(&rcu_barrier_completion); mutex_unlock(&rcu_barrier_mutex); } |