add_tgid_to_list(tgid, tgid_list);

Hi Olivier,

As far as the command output, for the sake of consistency,
the only thing I'd like to see added would be the task header
of the group leader as the first line of the output, and
it seems to me that all the pre-thread output should be
indented.

So, taking your example, it would look like:

crash> sig -g 27491
PID: 27489  TASK: f606b560  CPU: 0   COMMAND:
"sig_procthread"
SIGNAL_STRUCT: f78f8380  COUNT: 3
SIG SIGACTION  HANDLER      
MASK       FLAGS
[1]  c1f3f104  SIG_DFL 0000000000000000 0
...
  PID: 27489  TASK: f606b560  CPU: 0  
COMMAND: "sig_procthread"
  SIGPENDING: no
  ...
  PID: 27490  TASK: f7d09020  CPU: 0  
COMMAND: "sig_procthread"
  SIGPENDING: no
  ...
  PID: 27491  TASK: f544f020  CPU: 1  
COMMAND: "sig_procthread"
  SIGPENDING: no
  ...
crash>

However, as far as your implementation goes, I'd prefer not
to mix the "ps" and "sig" functionality in the singular
show_tgid_list() function.  There are a few reasons:

(1) it makes the function hard to understand and maintain.
(2) the "ps" command is not context-sensitive, while the
    "sig" command is.
(3) the "sig" command is accessible from "foreach sig", but
    the foreach() command currently doesn't pass
any flags
    into the "sig" handling functions.

And speaking of "foreach", "foreach sig -g" would be an ideal
way to display signal handling in a per-thread-group manner.
However, support for "foreach sig -g" would be a little tricky,
because as it is now, foreach() would pass *all* tasks to the
signal handling function -- which would redundantly show the same
information for each task in a multi-threaded process, and
we don't want that...

So there would have to be a mechanism where a list of tgids
from among the larger list of tasks would have to gathered first,
and then only that tgid list would be passed on to the signal
displaying code.

Currently the foreach() function does this in a loop for
each task that is selected:

case FOREACH_SIG:

pc->curcmd = "sig";

do_sig(tc->task, FOREACH_SIG,

fd->reference ? ref : NULL);

break;

If the -g flag is supported, it could do something like
this instead, and post-process the subset of tgid's taken
from the full task list:

case FOREACH_SIG:

if (fd->flags & FOREACH_g_FLAG) {

tgid = task_tgid(tc->task);

/*

*  Add tgid some list of tgid's,

*  ignoring tgid if it's already

*  on the list...

*/

add_tgid_to_list(tgid, tgid_list);

} else {

pc->curcmd = "sig";

do_sig(tc->task, FOREACH_SIG,

fd->reference ? ref : NULL);

}

break;

The memory buffer for the list of tgid's could be pre-allocated
in the pre-processing part of foreach(), perhaps by GETBUF()'ing
enough space for one-tgid-per-the-total-number-of-tasks running
on the system.  RUNNING_TASKS() will give you that number,
and
that would guarantee that the buffer would be large enough.

Then, in the post-processing part of foreach(), it could call
your new signal-handling function for each tgid in the list.

In any case, regardless whether you want to implement the -g
support from "foreach sig", please update your patch to not modify
show_tgid_list(), but instead create a new, similar, signal-specific
function that you can call from cmd_sig().  I can write the
"foreach"
part if you don't want to bother with that...

And go ahead and tinker with the "sig" help pages as well...

Thanks,
  Dave