[PATCH] Kprobes: preempt_disable/enable() simplification
Reorganize the preempt_disable/enable calls to eliminate the extra preempt
depth. Changes based on Paul McKenney's review suggestions for the kprobes
RCU changeset.
Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/ia64/kernel/kprobes.c b/arch/ia64/kernel/kprobes.c
index fddbac3..96736a1 100644
--- a/arch/ia64/kernel/kprobes.c
+++ b/arch/ia64/kernel/kprobes.c
@@ -389,11 +389,11 @@
spin_unlock_irqrestore(&kretprobe_lock, flags);
preempt_enable_no_resched();
- /*
- * By returning a non-zero value, we are telling
- * kprobe_handler() that we have handled unlocking
- * and re-enabling preemption
- */
+ /*
+ * By returning a non-zero value, we are telling
+ * kprobe_handler() that we don't want the post_handler
+ * to run (and have re-enabled preemption)
+ */
return 1;
}
@@ -604,7 +604,14 @@
int ret = 0;
struct pt_regs *regs = args->regs;
kprobe_opcode_t *addr = (kprobe_opcode_t *)instruction_pointer(regs);
- struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+ struct kprobe_ctlblk *kcb;
+
+ /*
+ * We don't want to be preempted for the entire
+ * duration of kprobe processing
+ */
+ preempt_disable();
+ kcb = get_kprobe_ctlblk();
/* Handle recursion cases */
if (kprobe_running()) {
@@ -659,11 +666,6 @@
goto no_kprobe;
}
- /*
- * This preempt_disable() matches the preempt_enable_no_resched()
- * in post_kprobes_handler()
- */
- preempt_disable();
set_current_kprobe(p, kcb);
kcb->kprobe_status = KPROBE_HIT_ACTIVE;
@@ -681,6 +683,7 @@
return 1;
no_kprobe:
+ preempt_enable_no_resched();
return ret;
}
@@ -716,9 +719,6 @@
struct kprobe *cur = kprobe_running();
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
- if (!cur)
- return 0;
-
if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
return 1;
@@ -737,7 +737,6 @@
struct die_args *args = (struct die_args *)data;
int ret = NOTIFY_DONE;
- rcu_read_lock();
switch(val) {
case DIE_BREAK:
if (pre_kprobes_handler(args))
@@ -748,12 +747,15 @@
ret = NOTIFY_STOP;
break;
case DIE_PAGE_FAULT:
- if (kprobes_fault_handler(args->regs, args->trapnr))
+ /* kprobe_running() needs smp_processor_id() */
+ preempt_disable();
+ if (kprobe_running() &&
+ kprobes_fault_handler(args->regs, args->trapnr))
ret = NOTIFY_STOP;
+ preempt_enable();
default:
break;
}
- rcu_read_unlock();
return ret;
}
@@ -785,6 +787,7 @@
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
*regs = kcb->jprobe_saved_regs;
+ preempt_enable_no_resched();
return 1;
}