ring-buffer: Move disabled check into preempt disable section

[safe/jmp/linux-2.6] / kernel / hw_breakpoint.c

diff --git a/kernel/hw_breakpoint.c b/kernel/hw_breakpoint.c
index 03a0773..967e661 100644 (file)
--- a/kernel/hw_breakpoint.c
+++ b/kernel/hw_breakpoint.c
@@ -40,6 +40,7 @@
 #include <linux/percpu.h>
 #include <linux/sched.h>
 #include <linux/init.h>
+#include <linux/cpu.h>
 #include <linux/smp.h>
 
 #include <linux/hw_breakpoint.h>
@@ -96,7 +97,7 @@ static int task_bp_pinned(struct task_struct *tsk)
 
        list = &ctx->event_list;
 
-       spin_lock_irqsave(&ctx->lock, flags);
+       raw_spin_lock_irqsave(&ctx->lock, flags);
 
        /*
         * The current breakpoint counter is not included in the list
@@ -107,7 +108,7 @@ static int task_bp_pinned(struct task_struct *tsk)
                        count++;
        }
 
-       spin_unlock_irqrestore(&ctx->lock, flags);
+       raw_spin_unlock_irqrestore(&ctx->lock, flags);
 
        return count;
 }
@@ -242,38 +243,70 @@ static void toggle_bp_slot(struct perf_event *bp, bool enable)
  *       ((per_cpu(nr_bp_flexible, *) > 1) + max(per_cpu(nr_cpu_bp_pinned, *))
  *            + max(per_cpu(nr_task_bp_pinned, *))) < HBP_NUM
  */
-int reserve_bp_slot(struct perf_event *bp)
+static int __reserve_bp_slot(struct perf_event *bp)
 {
        struct bp_busy_slots slots = {0};
-       int ret = 0;
-
-       mutex_lock(&nr_bp_mutex);
 
        fetch_bp_busy_slots(&slots, bp);
 
        /* Flexible counters need to keep at least one slot */
-       if (slots.pinned + (!!slots.flexible) == HBP_NUM) {
-               ret = -ENOSPC;
-               goto end;
-       }
+       if (slots.pinned + (!!slots.flexible) == HBP_NUM)
+               return -ENOSPC;
 
        toggle_bp_slot(bp, true);
 
-end:
+       return 0;
+}
+
+int reserve_bp_slot(struct perf_event *bp)
+{
+       int ret;
+
+       mutex_lock(&nr_bp_mutex);
+
+       ret = __reserve_bp_slot(bp);
+
        mutex_unlock(&nr_bp_mutex);
 
        return ret;
 }
 
+static void __release_bp_slot(struct perf_event *bp)
+{
+       toggle_bp_slot(bp, false);
+}
+
 void release_bp_slot(struct perf_event *bp)
 {
        mutex_lock(&nr_bp_mutex);
 
-       toggle_bp_slot(bp, false);
+       __release_bp_slot(bp);
 
        mutex_unlock(&nr_bp_mutex);
 }
 
+/*
+ * Allow the kernel debugger to reserve breakpoint slots without
+ * taking a lock using the dbg_* variant of for the reserve and
+ * release breakpoint slots.
+ */
+int dbg_reserve_bp_slot(struct perf_event *bp)
+{
+       if (mutex_is_locked(&nr_bp_mutex))
+               return -1;
+
+       return __reserve_bp_slot(bp);
+}
+
+int dbg_release_bp_slot(struct perf_event *bp)
+{
+       if (mutex_is_locked(&nr_bp_mutex))
+               return -1;
+
+       __release_bp_slot(bp);
+
+       return 0;
+}
 
 int register_perf_hw_breakpoint(struct perf_event *bp)
 {
@@ -295,6 +328,10 @@ int register_perf_hw_breakpoint(struct perf_event *bp)
        if (!bp->attr.disabled || !bp->overflow_handler)
                ret = arch_validate_hwbkpt_settings(bp, bp->ctx->task);
 
+       /* if arch_validate_hwbkpt_settings() fails then release bp slot */
+       if (ret)
+               release_bp_slot(bp);
+
        return ret;
 }
 
@@ -320,18 +357,40 @@ EXPORT_SYMBOL_GPL(register_user_hw_breakpoint);
  * @triggered: callback to trigger when we hit the breakpoint
  * @tsk: pointer to 'task_struct' of the process to which the address belongs
  */
-struct perf_event *
-modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr)
+int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr)
 {
-       /*
-        * FIXME: do it without unregistering
-        * - We don't want to lose our slot
-        * - If the new bp is incorrect, don't lose the older one
-        */
-       unregister_hw_breakpoint(bp);
+       u64 old_addr = bp->attr.bp_addr;
+       u64 old_len = bp->attr.bp_len;
+       int old_type = bp->attr.bp_type;
+       int err = 0;
+
+       perf_event_disable(bp);
+
+       bp->attr.bp_addr = attr->bp_addr;
+       bp->attr.bp_type = attr->bp_type;
+       bp->attr.bp_len = attr->bp_len;
+
+       if (attr->disabled)
+               goto end;
+
+       err = arch_validate_hwbkpt_settings(bp, bp->ctx->task);
+       if (!err)
+               perf_event_enable(bp);
+
+       if (err) {
+               bp->attr.bp_addr = old_addr;
+               bp->attr.bp_type = old_type;
+               bp->attr.bp_len = old_len;
+               if (!bp->attr.disabled)
+                       perf_event_enable(bp);
+
+               return err;
+       }
+
+end:
+       bp->attr.disabled = attr->disabled;
 
-       return perf_event_create_kernel_counter(attr, -1, bp->ctx->task->pid,
-                                               bp->overflow_handler);
+       return 0;
 }
 EXPORT_SYMBOL_GPL(modify_user_hw_breakpoint);
 
@@ -366,7 +425,8 @@ register_wide_hw_breakpoint(struct perf_event_attr *attr,
        if (!cpu_events)
                return ERR_PTR(-ENOMEM);
 
-       for_each_possible_cpu(cpu) {
+       get_online_cpus();
+       for_each_online_cpu(cpu) {
                pevent = per_cpu_ptr(cpu_events, cpu);
                bp = perf_event_create_kernel_counter(attr, cpu, -1, triggered);
 
@@ -377,18 +437,20 @@ register_wide_hw_breakpoint(struct perf_event_attr *attr,
                        goto fail;
                }
        }
+       put_online_cpus();
 
        return cpu_events;
 
 fail:
-       for_each_possible_cpu(cpu) {
+       for_each_online_cpu(cpu) {
                pevent = per_cpu_ptr(cpu_events, cpu);
                if (IS_ERR(*pevent))
                        break;
                unregister_hw_breakpoint(*pevent);
        }
+       put_online_cpus();
+
        free_percpu(cpu_events);
-       /* return the error if any */
        return ERR_PTR(err);
 }
 EXPORT_SYMBOL_GPL(register_wide_hw_breakpoint);