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Message-ID: <20131015094035.GA12416@quack.suse.cz>
Date: Tue, 15 Oct 2013 11:40:35 +0200
From: Jan Kara <jack@...e.cz>
To: Jens Axboe <axboe@...nel.dk>
Cc: LKML <linux-kernel@...r.kernel.org>, Jan Kara <jack@...e.cz>
Subject: Re: [PATCH] blktrace: Send BLK_TN_PROCESS events to all running
traces
On Mon 23-09-13 13:37:23, Jan Kara wrote:
> On Tue 17-09-13 22:30:31, Jan Kara wrote:
> > Currently each task sends BLK_TN_PROCESS event to the first traced
> > device it interacts with after a new trace is started. When there are
> > several traced devices and the task accesses more devices, this logic
> > can result in BLK_TN_PROCESS being sent several times to some devices
> > while it is never sent to other devices. Thus blkparse doesn't display
> > command name when parsing some blktrace files.
> >
> > Fix the problem by sending BLK_TN_PROCESS event to all traced devices
> > when a task interacts with any of them.
> Jens, any opinion about this?
Jens, ping? I guess this patch fell through cracks...
Honza
> > Signed-off-by: Jan Kara <jack@...e.cz>
> > ---
> > include/linux/blktrace_api.h | 2 ++
> > kernel/trace/blktrace.c | 33 +++++++++++++++++++++++++++------
> > 2 files changed, 29 insertions(+), 6 deletions(-)
> >
> > diff --git a/include/linux/blktrace_api.h b/include/linux/blktrace_api.h
> > index 7c2e030..a12f6ed 100644
> > --- a/include/linux/blktrace_api.h
> > +++ b/include/linux/blktrace_api.h
> > @@ -5,6 +5,7 @@
> > #include <linux/relay.h>
> > #include <linux/compat.h>
> > #include <uapi/linux/blktrace_api.h>
> > +#include <linux/list.h>
> >
> > #if defined(CONFIG_BLK_DEV_IO_TRACE)
> >
> > @@ -23,6 +24,7 @@ struct blk_trace {
> > struct dentry *dir;
> > struct dentry *dropped_file;
> > struct dentry *msg_file;
> > + struct list_head running_list;
> > atomic_t dropped;
> > };
> >
> > diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
> > index b8b8560..7f727b3 100644
> > --- 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;
> > }
> > --
> > 1.8.1.4
> >
> --
> Jan Kara <jack@...e.cz>
> SUSE Labs, CR
--
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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