lkml.org 
[lkml]   [2011]   [Aug]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    SubjectRe: [PATCH v6 2/2] Output stall data in debugfs
    From
    On Thu, Aug 11, 2011 at 12:43 PM, Peter Zijlstra <peterz@infradead.org> wrote:
    > zakmagnus seems to bounce, so who am I talking to anyway..
    >
    > On Thu, 2011-08-11 at 21:35 +0200, Peter Zijlstra wrote:
    >>
    >> static void show_stall_trace(struct seq_file *f, void *v)
    >> {
    >>         struct stall *s = f->private;
    >>         int i, idx = ACCESS_ONCE(s->idx);
    >>
    >>         mutex_lock(&stall_mutex);
    >>
    >>         raw_spin_lock(&s->lock[idx]);
    >>         seq_printf(f, "stall: %d\n", s->worst);
    >>         for (i = 0; i < s->trace[idx].nr_entries; i++) {
    >>                 seq_printf(f, "[<%pK>] %pS\n",
    >>                         (void *)s->trace->entries[i],
    >>                         (void *)s->trace->entries[i]);
    >>         }
    >>         raw_spin_unlock(&s->lock[idx]);
    >>
    >>         mutex_unlock(&stall_mutex);
    >> }
    >>
    >>
    >> Yes its racy on s->worst, but who cares (if you do care you can keep a
    >> copy in s->delay[idx] or so). Also, it might be better to not do the
    >> spinlock but simply use an atomic bitop to set an in-use flag, there is
    >> no reason to disable preemption over the seq_printf() loop.
    >
    > That also cures another problem you have, a seq_file buffer is only 1
    > page large, you should be using the seqfile iterator interface and print
    > one line at a time.. now clearly that won't work with preemption
    > disabled either.
    I didn't want to hold on to a lock while the lines were iterated over,
    and instead just dump it in one go. I guess it's not a big deal to do
    that, though. Nonetheless, is one page not enough?
    --
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2011-08-11 21:53    [W:0.025 / U:1.136 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site