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author | Josh Boyer <jwboyer@redhat.com> | 2011-08-15 10:06:52 -0400 |
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committer | Josh Boyer <jwboyer@redhat.com> | 2011-08-15 10:06:52 -0400 |
commit | 6920e17ebc39b209f18c9fcf8cccf19b3b984560 (patch) | |
tree | 0b8caccd4041abb4c068dfe14b6eb9de711e852d /rcu-avoid-just-onlined-cpu-resched.patch | |
parent | f1b16b1fca682d767ea2cc2f91837fd34a4bf577 (diff) | |
download | kernel-6920e17ebc39b209f18c9fcf8cccf19b3b984560.tar.gz kernel-6920e17ebc39b209f18c9fcf8cccf19b3b984560.tar.xz kernel-6920e17ebc39b209f18c9fcf8cccf19b3b984560.zip |
Linux-3.1-rc2
Add better fix from Paul McKenney for rcu scheduling issue (rhbz 726877)
Diffstat (limited to 'rcu-avoid-just-onlined-cpu-resched.patch')
-rw-r--r-- | rcu-avoid-just-onlined-cpu-resched.patch | 47 |
1 files changed, 47 insertions, 0 deletions
diff --git a/rcu-avoid-just-onlined-cpu-resched.patch b/rcu-avoid-just-onlined-cpu-resched.patch new file mode 100644 index 000000000..517f37591 --- /dev/null +++ b/rcu-avoid-just-onlined-cpu-resched.patch @@ -0,0 +1,47 @@ +rcu: Avoid having just-onlined CPU resched itself when RCU is idle + +CPUs set rdp->qs_pending when coming online to resolve races with +grace-period start. However, this means that if RCU is idle, the +just-onlined CPU might needlessly send itself resched IPIs. Adjust +the online-CPU initialization to avoid this, and also to correctly +cause the CPU to respond to the current grace period if needed. + +Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> +--- + kernel/rcutree.c | 13 +++++++++---- + 1 files changed, 9 insertions(+), 4 deletions(-) + +diff --git a/kernel/rcutree.c b/kernel/rcutree.c +index ba06207..472d6b2 100644 +--- a/kernel/rcutree.c ++++ b/kernel/rcutree.c +@@ -1865,8 +1865,6 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible) + + /* Set up local state, ensuring consistent view of global state. */ + raw_spin_lock_irqsave(&rnp->lock, flags); +- rdp->passed_quiesc = 0; /* We could be racing with new GP, */ +- rdp->qs_pending = 1; /* so set up to respond to current GP. */ + rdp->beenonline = 1; /* We have now been online. */ + rdp->preemptible = preemptible; + rdp->qlen_last_fqs_check = 0; +@@ -1891,8 +1889,15 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible) + rnp->qsmaskinit |= mask; + mask = rnp->grpmask; + if (rnp == rdp->mynode) { +- rdp->gpnum = rnp->completed; /* if GP in progress... */ +- rdp->completed = rnp->completed; ++ /* ++ * If there is a grace period in progress, we will ++ * set up to wait for it next time we run the ++ * RCU core code. ++ */ ++ rdp->gpnum = rnp->completed; ++ rdp->completed = rnp->completed; ++ rdp->passed_quiesc = 0; ++ rdp->qs_pending = 0; + rdp->passed_quiesc_completed = rnp->completed - 1; + } + raw_spin_unlock(&rnp->lock); /* irqs already disabled. */ +-- +1.7.6 + |