When I'm using below ktap script to tracing all event tracepoints, without
this patch, the system will hang in few seconds, the patch indeed fix the
problem as the changelog pointed.
function eventfun (e) {
printf("%d %d\t%s\t%s", cpu(), pid(), execname(), e.annotate)
}
kdebug.probe("tp:", eventfun)
kdebug.probe_end(function () {
printf("probe end\n")
})
This patch is old, I can found the original patch discussion in 2007.
http://marc.info/?l=linux-kernel&m=
118544794717162&w=2 (In that mail
thread, the patch didn't fix that problem, but it fix the problem I
encountered now)
Ingo's original changelog:
Remove timer calls (!!!) from deep within the tracing infrastructure.
This was totally bogus code that can cause lockups and worse.
Poll the buffer every 2 jiffies for now.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: "zhangwei(Jovi)" <jovi.zhangwei@huawei.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric Dumazet <edumazet@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
{
struct rchan_buf *buf = (struct rchan_buf *)data;
wake_up_interruptible(&buf->read_wait);
+ /*
+ * Stupid polling for now:
+ */
+ mod_timer(&buf->timer, jiffies + 1);
}
/**
init_waitqueue_head(&buf->read_wait);
kref_init(&buf->kref);
setup_timer(&buf->timer, wakeup_readers, (unsigned long)buf);
+ mod_timer(&buf->timer, jiffies + 1);
} else
del_timer_sync(&buf->timer);
else
buf->early_bytes += buf->chan->subbuf_size -
buf->padding[old_subbuf];
- smp_mb();
- if (waitqueue_active(&buf->read_wait))
- /*
- * Calling wake_up_interruptible() from here
- * will deadlock if we happen to be logging
- * from the scheduler (trying to re-grab
- * rq->lock), so defer it.
- */
- mod_timer(&buf->timer, jiffies + 1);
}
old = buf->data;