kprobes: Disable booster when CONFIG_PREEMPT=y

Disable kprobe booster when CONFIG_PREEMPT=y at this time,
because it can't ensure that all kernel threads preempted on
kprobe's boosted slot run out from the slot even using
freeze_processes().

The booster on preemptive kernel will be resumed if
synchronize_tasks() or something like that is introduced.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: systemtap <systemtap@sources.redhat.com>
Cc: DLE <dle-develop@lists.sourceforge.net>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jim Keniston <jkenisto@us.ibm.com>
Cc: Mathieu Desnoyers <compudj@krystal.dyndns.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <20100202214904.4694.24330.stgit@dhcp-100-2-132.bos.redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

3 files changed, 4 insertions, 29 deletions

diff --git a/arch/ia64/kernel/kprobes.c b/arch/ia64/kernel/kprobes.c
index 9adac441ac9b..7026b29e277a 100644
--- a/arch/ia64/kernel/kprobes.c
+++ b/arch/ia64/kernel/kprobes.c
@@ -870,7 +870,7 @@ static int __kprobes pre_kprobes_handler(struct die_args *args)
                 return 1;
 
 ss_probe:
-#if !defined(CONFIG_PREEMPT) || defined(CONFIG_FREEZER)
+#if !defined(CONFIG_PREEMPT)
         if (p->ainsn.inst_flag == INST_FLAG_BOOSTABLE && !p->post_handler) {
                 /* Boost up -- we can execute copied instructions directly */
                 ia64_psr(regs)->ri = p->ainsn.slot;
diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c
index 5b8c7505b3bc..9453815138fa 100644
--- a/arch/x86/kernel/kprobes.c
+++ b/arch/x86/kernel/kprobes.c
@@ -429,7 +429,7 @@ void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 static void __kprobes setup_singlestep(struct kprobe *p, struct pt_regs *regs,
                                        struct kprobe_ctlblk *kcb)
 {
-#if !defined(CONFIG_PREEMPT) || defined(CONFIG_FREEZER)
+#if !defined(CONFIG_PREEMPT)
         if (p->ainsn.boostable == 1 && !p->post_handler) {
                 /* Boost up -- we can execute copied instructions directly */
                 reset_current_kprobe();
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index b7df302a0204..9907a03c29f6 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -124,30 +124,6 @@ static LIST_HEAD(kprobe_insn_pages);
 static int kprobe_garbage_slots;
 static int collect_garbage_slots(void);
 
-static int __kprobes check_safety(void)
-{
-        int ret = 0;
-#if defined(CONFIG_PREEMPT) && defined(CONFIG_FREEZER)
-        ret = freeze_processes();
-        if (ret == 0) {
-                struct task_struct *p, *q;
-                do_each_thread(p, q) {
-                        if (p != current && p->state == TASK_RUNNING &&
-                            p->pid != 0) {
-                                printk("Check failed: %s is running\n",p->comm);
-                                ret = -1;
-                                goto loop_end;
-                        }
-                } while_each_thread(p, q);
-        }
-loop_end:
-        thaw_processes();
-#else
-        synchronize_sched();
-#endif
-        return ret;
-}
-
 /**
  * __get_insn_slot() - Find a slot on an executable page for an instruction.
  * We allocate an executable page if there's no room on existing ones.
@@ -235,9 +211,8 @@ static int __kprobes collect_garbage_slots(void)
 {
         struct kprobe_insn_page *kip, *next;
 
-        /* Ensure no-one is preepmted on the garbages */
-        if (check_safety())
-                return -EAGAIN;
+        /* Ensure no-one is interrupted on the garbages */
+        synchronize_sched();
 
         list_for_each_entry_safe(kip, next, &kprobe_insn_pages, list) {
                 int i;