[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/i386/kernel/kprobes.c b/arch/i386/kernel/kprobes.c
index ad46929..32b0c24 100644
--- a/arch/i386/kernel/kprobes.c
+++ b/arch/i386/kernel/kprobes.c
@@ -153,7 +153,14 @@
int ret = 0;
kprobe_opcode_t *addr = NULL;
unsigned long *lp;
- 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();
/* Check if the application is using LDT entry for its code segment and
* calculate the address by reading the base address from the LDT entry.
@@ -221,11 +228,6 @@
goto no_kprobe;
}
- /*
- * This preempt_disable() matches the preempt_enable_no_resched()
- * in post_kprobe_handler()
- */
- preempt_disable();
set_current_kprobe(p, regs, kcb);
kcb->kprobe_status = KPROBE_HIT_ACTIVE;
@@ -239,6 +241,7 @@
return 1;
no_kprobe:
+ preempt_enable_no_resched();
return ret;
}
@@ -310,8 +313,8 @@
/*
* By returning a non-zero value, we are telling
- * kprobe_handler() that we have handled unlocking
- * and re-enabling preemption
+ * kprobe_handler() that we don't want the post_handler
+ * to run (and have re-enabled preemption)
*/
return 1;
}
@@ -455,7 +458,6 @@
struct die_args *args = (struct die_args *)data;
int ret = NOTIFY_DONE;
- rcu_read_lock();
switch (val) {
case DIE_INT3:
if (kprobe_handler(args->regs))
@@ -467,14 +469,16 @@
break;
case DIE_GPF:
case DIE_PAGE_FAULT:
+ /* kprobe_running() needs smp_processor_id() */
+ preempt_disable();
if (kprobe_running() &&
kprobe_fault_handler(args->regs, args->trapnr))
ret = NOTIFY_STOP;
+ preempt_enable();
break;
default:
break;
}
- rcu_read_unlock();
return ret;
}
@@ -537,6 +541,7 @@
*regs = kcb->jprobe_saved_regs;
memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack,
MIN_STACK_SIZE(stack_addr));
+ preempt_enable_no_resched();
return 1;
}
return 0;