On Fri, 30 Jun 2017 11:17:50 -0600 Michael Sartain <mikes...@fastmail.com> wrote:
> Export the cached pid / tgid mappings to userspace. This allows user > apps to translate the pids from a trace to their respective thread > group. > > Example saved_tgids file with pid / tgid values separated by ' ': > > # cat saved_tgids > 1048 1048 > 1047 1047 > 7 7 > 1049 1047 > 1054 1047 > 1053 1047 > > [ Impact: let userspace apps reading binary buffer know tgid's ] Impact line? Linus put a kibosh on this a while ago... https://lkml.org/lkml/2009/4/15/296 Although, I will admit that this line is actually useful. Just remove the brackets. > > Signed-off-by: Michael Sartain <mikes...@fastmail.com> > --- > kernel/trace/trace.c | 60 > +++++++++++++++++++++++++++++++++++++++++++++++++++- > 1 file changed, 59 insertions(+), 1 deletion(-) > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index 68c214b..ca84c97 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -4692,6 +4692,7 @@ static const struct file_operations tracing_readme_fops > = { > static void *saved_cmdlines_next(struct seq_file *m, void *v, loff_t *pos) > { > unsigned int *ptr = v; > + long tgid_check = (long) m->private; I really don't like the subtle use of having m->private != NULL mean this is for tgid listing. In fact, I don't see the purpose of reusing the seq code. The cmdlines and tgid map are quite different. Just create its own functions. I don't see the benefit of trying to reuse this except for making the code more complex. -- Steve > > if (*pos || m->count) > ptr++; > @@ -4702,6 +4703,8 @@ static void *saved_cmdlines_next(struct seq_file *m, > void *v, loff_t *pos) > ptr++) { > if (*ptr == -1 || *ptr == NO_CMDLINE_MAP) > continue; > + if (tgid_check && !trace_find_tgid(*ptr)) > + continue; > > return ptr; > } > @@ -4713,6 +4716,10 @@ static void *saved_cmdlines_start(struct seq_file *m, > loff_t *pos) > { > void *v; > loff_t l = 0; > + long tgid_check = (long) m->private; > + > + if (tgid_check && !tgid_map) > + return NULL; > > preempt_disable(); > arch_spin_lock(&trace_cmdline_lock); > @@ -4743,6 +4750,14 @@ static int saved_cmdlines_show(struct seq_file *m, > void *v) > return 0; > } >
