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Subject[PATCH] fixes for rcu_offline_cpu, rcu_move_batch (2.6.8-rc2)
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Hi,

rcu_offline_cpu and rcu_move_batch have been broken since the
list_head's in struct rcu_head and struct rcu_data were replaced with
singly-linked lists:

CC kernel/rcupdate.o
kernel/rcupdate.c: In function `rcu_move_batch':
kernel/rcupdate.c:222: warning: passing arg 2 of `list_add_tail' from
incompatible pointer type
kernel/rcupdate.c: In function `rcu_offline_cpu':
kernel/rcupdate.c:239: warning: passing arg 1 of `rcu_move_batch' from
incompatible pointer type
kernel/rcupdate.c:240: warning: passing arg 1 of `rcu_move_batch' from
incompatible pointer type
kernel/rcupdate.c:236: warning: label `unlock' defined but not used

Kernel crashes when you try to offline a cpu, not surprisingly.

It also looks like rcu_move_batch isn't preempt-safe so I touched that
up, and got rid of an unused label in rcu_offline_cpu.

This fixes the crash for me; does it look ok?


Signed-off-by: Nathan Lynch <nathanl@austin.ibm.com>

diff -prauNX /home/nathanl/working/dontdiff 2.6.8-rc2/kernel/rcupdate.c 2.6.8-rc2-ntl/kernel/rcupdate.c
--- 2.6.8-rc2/kernel/rcupdate.c 2004-07-23 19:58:35.000000000 -0500
+++ 2.6.8-rc2-ntl/kernel/rcupdate.c 2004-07-26 13:41:15.000000000 -0500
@@ -210,16 +210,18 @@ 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 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();
+
+ while (list != NULL) {
+ *RCU_nxttail(cpu) = list;
+ RCU_nxttail(cpu) = &list->next;
+ list = list->next;
}
local_irq_enable();
}
@@ -233,11 +235,10 @@ 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_move_batch(RCU_nxtlist(cpu));

tasklet_kill_immediate(&RCU_tasklet(cpu), cpu);
}

-
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