blktrace: Send BLK_TN_PROCESS events to all running traces

[~andy/linux] / kernel / trace / blktrace.c

diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index b8b8560bfb95af43d36817d743f6218f01ed0edb..7f727b34280d7315ba09f6ff9f2b54457e4c1ed7 100644 (file)
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -26,6 +26,7 @@
 #include <linux/export.h>
 #include <linux/time.h>
 #include <linux/uaccess.h>
+#include <linux/list.h>
 
 #include <trace/events/block.h>
 
@@ -38,6 +39,9 @@ static unsigned int blktrace_seq __read_mostly = 1;
 static struct trace_array *blk_tr;
 static bool blk_tracer_enabled __read_mostly;
 
+static LIST_HEAD(running_trace_list);
+static __cacheline_aligned_in_smp DEFINE_SPINLOCK(running_trace_lock);
+
 /* Select an alternative, minimalistic output than the original one */
 #define TRACE_BLK_OPT_CLASSIC  0x1
 
@@ -107,10 +111,18 @@ record_it:
  * Send out a notify for this process, if we haven't done so since a trace
  * started
  */
-static void trace_note_tsk(struct blk_trace *bt, struct task_struct *tsk)
+static void trace_note_tsk(struct task_struct *tsk)
 {
+       unsigned long flags;
+       struct blk_trace *bt;
+
        tsk->btrace_seq = blktrace_seq;
-       trace_note(bt, tsk->pid, BLK_TN_PROCESS, tsk->comm, sizeof(tsk->comm));
+       spin_lock_irqsave(&running_trace_lock, flags);
+       list_for_each_entry(bt, &running_trace_list, running_list) {
+               trace_note(bt, tsk->pid, BLK_TN_PROCESS, tsk->comm,
+                          sizeof(tsk->comm));
+       }
+       spin_unlock_irqrestore(&running_trace_lock, flags);
 }
 
 static void trace_note_time(struct blk_trace *bt)
@@ -229,16 +241,15 @@ static void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
                goto record_it;
        }
 
+       if (unlikely(tsk->btrace_seq != blktrace_seq))
+               trace_note_tsk(tsk);
+
        /*
         * A word about the locking here - we disable interrupts to reserve
         * some space in the relay per-cpu buffer, to prevent an irq
         * from coming in and stepping on our toes.
         */
        local_irq_save(flags);
-
-       if (unlikely(tsk->btrace_seq != blktrace_seq))
-               trace_note_tsk(bt, tsk);
-
        t = relay_reserve(bt->rchan, sizeof(*t) + pdu_len);
        if (t) {
                sequence = per_cpu_ptr(bt->sequence, cpu);
@@ -477,6 +488,7 @@ int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
        bt->dir = dir;
        bt->dev = dev;
        atomic_set(&bt->dropped, 0);
+       INIT_LIST_HEAD(&bt->running_list);
 
        ret = -EIO;
        bt->dropped_file = debugfs_create_file("dropped", 0444, dir, bt,
@@ -601,6 +613,9 @@ int blk_trace_startstop(struct request_queue *q, int start)
                        blktrace_seq++;
                        smp_mb();
                        bt->trace_state = Blktrace_running;
+                       spin_lock_irq(&running_trace_lock);
+                       list_add(&bt->running_list, &running_trace_list);
+                       spin_unlock_irq(&running_trace_lock);
 
                        trace_note_time(bt);
                        ret = 0;
@@ -608,6 +623,9 @@ int blk_trace_startstop(struct request_queue *q, int start)
        } else {
                if (bt->trace_state == Blktrace_running) {
                        bt->trace_state = Blktrace_stopped;
+                       spin_lock_irq(&running_trace_lock);
+                       list_del_init(&bt->running_list);
+                       spin_unlock_irq(&running_trace_lock);
                        relay_flush(bt->rchan);
                        ret = 0;
                }
@@ -1472,6 +1490,9 @@ static int blk_trace_remove_queue(struct request_queue *q)
        if (atomic_dec_and_test(&blk_probes_ref))
                blk_unregister_tracepoints();
 
+       spin_lock_irq(&running_trace_lock);
+       list_del(&bt->running_list);
+       spin_unlock_irq(&running_trace_lock);
        blk_trace_free(bt);
        return 0;
 }