Re: [PATCH] RCU - rcu-cpu-offline-fix [2/3]
From: Dipankar Sarma (dipankar_at_in.ibm.com)
Date: 07/31/04
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Date: Sat, 31 Jul 2004 14:31:08 +0530 To: Andrew Morton <akpm@osdl.org>
Andrew,
This patch replaces fixes-for-rcu_offline_cpu-rcu_move_batch-268-rc2.patch
in -mm tree. Same thing, but I needed to add the tail pointers anyway
for the RCU lists. That allows callbacks lists to be added to the
tail without iterating, so an optimized version of Nathan's patch.
I have sanity tested cpu hotplug on a ppc64 box with this patch.
Thanks
Dipankar
This fixes the RCU cpu offline code which was broken by singly-linked
RCU changes. Nathan pointed out the problems and submitted a patch
for this. This is an optimal fix - no need to iterate through
the list of callbacks, just use the tail pointers and attach the
list from the dead cpu.
Signed-off-by: Nathan Lynch <nathanl@austin.ibm.com>
Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
include/linux/rcupdate.h | 2 ++
kernel/rcupdate.c | 22 +++++++++++-----------
2 files changed, 13 insertions(+), 11 deletions(-)
diff -puN kernel/rcupdate.c~rcu-cpu-offline-fix kernel/rcupdate.c
--- linux-2.6.8-rc2-rcu/kernel/rcupdate.c~rcu-cpu-offline-fix 2004-07-29 16:06:03.000000000 +0530
+++ linux-2.6.8-rc2-rcu-dipankar/kernel/rcupdate.c 2004-07-31 12:25:57.000000000 +0530
@@ -210,17 +210,15 @@ static void rcu_check_quiescent_state(vo
* locking requirements, the list it's pulling from has to belong to a cpu
* which is dead and hence not processing interrupts.
*/
-static void rcu_move_batch(struct list_head *list)
+static void rcu_move_batch(struct rcu_head *list, struct rcu_head **tail)
{
- struct list_head *entry;
- int cpu = smp_processor_id();
+ int cpu;
local_irq_disable();
- while (!list_empty(list)) {
- entry = list->next;
- list_del(entry);
- list_add_tail(entry, &RCU_nxtlist(cpu));
- }
+ cpu = smp_processor_id();
+ *RCU_nxttail(cpu) = list;
+ if (list)
+ RCU_nxttail(cpu) = tail;
local_irq_enable();
}
@@ -233,11 +231,10 @@ static void rcu_offline_cpu(int cpu)
spin_lock_bh(&rcu_state.mutex);
if (rcu_ctrlblk.cur != rcu_ctrlblk.completed)
cpu_quiet(cpu);
-unlock:
spin_unlock_bh(&rcu_state.mutex);
- rcu_move_batch(&RCU_curlist(cpu));
- rcu_move_batch(&RCU_nxtlist(cpu));
+ rcu_move_batch(RCU_curlist(cpu), RCU_curtail(cpu));
+ rcu_move_batch(RCU_nxtlist(cpu), RCU_nxttail(cpu));
tasklet_kill_immediate(&RCU_tasklet(cpu), cpu);
}
@@ -270,6 +267,7 @@ static void rcu_process_callbacks(unsign
!rcu_batch_before(rcu_ctrlblk.completed, RCU_batch(cpu))) {
rcu_list = RCU_curlist(cpu);
RCU_curlist(cpu) = NULL;
+ RCU_curtail(cpu) = &RCU_curlist(cpu);
}
local_irq_disable();
@@ -277,6 +275,7 @@ static void rcu_process_callbacks(unsign
int next_pending, seq;
RCU_curlist(cpu) = RCU_nxtlist(cpu);
+ RCU_curtail(cpu) = RCU_nxttail(cpu);
RCU_nxtlist(cpu) = NULL;
RCU_nxttail(cpu) = &RCU_nxtlist(cpu);
local_irq_enable();
@@ -318,6 +317,7 @@ static void __devinit rcu_online_cpu(int
{
memset(&per_cpu(rcu_data, cpu), 0, sizeof(struct rcu_data));
tasklet_init(&RCU_tasklet(cpu), rcu_process_callbacks, 0UL);
+ RCU_curtail(cpu) = &RCU_curlist(cpu);
RCU_nxttail(cpu) = &RCU_nxtlist(cpu);
RCU_quiescbatch(cpu) = rcu_ctrlblk.completed;
RCU_qs_pending(cpu) = 0;
diff -puN include/linux/rcupdate.h~rcu-cpu-offline-fix include/linux/rcupdate.h
--- linux-2.6.8-rc2-rcu/include/linux/rcupdate.h~rcu-cpu-offline-fix 2004-07-29 16:12:51.000000000 +0530
+++ linux-2.6.8-rc2-rcu-dipankar/include/linux/rcupdate.h 2004-07-31 12:25:44.000000000 +0530
@@ -98,6 +98,7 @@ struct rcu_data {
struct rcu_head *nxtlist;
struct rcu_head **nxttail;
struct rcu_head *curlist;
+ struct rcu_head **curtail;
};
DECLARE_PER_CPU(struct rcu_data, rcu_data);
@@ -111,6 +112,7 @@ extern struct rcu_ctrlblk rcu_ctrlblk;
#define RCU_nxtlist(cpu) (per_cpu(rcu_data, (cpu)).nxtlist)
#define RCU_curlist(cpu) (per_cpu(rcu_data, (cpu)).curlist)
#define RCU_nxttail(cpu) (per_cpu(rcu_data, (cpu)).nxttail)
+#define RCU_curtail(cpu) (per_cpu(rcu_data, (cpu)).curtail)
static inline int rcu_pending(int cpu)
{
_
-
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- Previous message: Dipankar Sarma: "[PATCH] RCU - cpu-offline-cleanup [1/3]"
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