Re: [PATCH] GDB checkpoint can't/shouldn't be possible with multiple threads on Linux

Kevin Pouget
2011-04-12T11:55:31Z

[-- Attachment #1: Type: text/plain, Size: 1403 bytes --]

> Next time please post ChangeLog entries as plaintext,
> separate from the patch.

2011-04-12 Kevin Pouget <kevin.pouget@st.com>

PR threads/12628

* linux-fork.c (checkpoint_command): Disallow checkpointing of
processes with multiple threads.
(inf_has_multiple_thread_cb): New function.

> > diff --git a/gdb/linux-fork.c b/gdb/linux-fork.c
> > index 7f654af..c137604 100644
> > --- a/gdb/linux-fork.c
> > +++ b/gdb/linux-fork.c
> > @@ -628,6 +628,11 @@ checkpoint_command (char *args, int from_tty)
> >    pid_t retpid;
> >    struct cleanup *old_chain;
> >
> > +  /* Ensure that the inferior is not multithreaded. */
>
> Double space after periods.

fixed

> > +  update_thread_list () ;
> > +  if (thread_count () > 1)
> > +    error (_("checkpoint: can't checkpoint multiple threads.")) ;
>
> You have spurious spaces before `;'.

fixed

> thread_count() returns the sum total number of threads of all
> inferiors/process.  You want the number of threads of the
> current process only.  AFAIR, there's no function handy that
> returns you that.  (Since you're interested in checking for multiple
> threads, you could use iterate_over_threads with a
> callback that returns true if it sees a second thread for a
> given process, so you don't really need to count all
> the threads.)

you're right, I updated the patch as suggested

thanks,

Kevin

[-- Attachment #2: checkpoint.diff --]
[-- Type: application/octet-stream, Size: 1304 bytes --]

diff --git a/gdb/linux-fork.c b/gdb/linux-fork.c
index 7f654af..8a18d42 100644
--- a/gdb/linux-fork.c
+++ b/gdb/linux-fork.c
@@ -616,6 +616,20 @@ linux_fork_checkpointing_p (int pid)
return (checkpointing_pid == pid);
}

+static int
+inf_has_multiple_thread_cb (struct thread_info *tp, void *data)
+{
+ int *has_multiple_threads = (int *) data;
+
+ gdb_assert(current_inferior() != NULL);
+
+ if (current_inferior()->pid == GET_PID(tp->ptid))
+ (*has_multiple_threads)++;
+
+ /* Stop the iteration if multiple threads have been detected. */
+ return *has_multiple_threads > 1;
+}
+
static void
checkpoint_command (char *args, int from_tty)
{
@@ -627,7 +641,16 @@ checkpoint_command (char *args, int from_tty)
struct fork_info *fp;
pid_t retpid;
struct cleanup *old_chain;
+ int has_multiple_threads = 0 ;
+
+ if (!target_has_execution) error (_("The program is not being run."));

+ /* Ensure that the inferior is not multithreaded. */
+ update_thread_list () ;
+ iterate_over_threads(inf_has_multiple_thread_cb, &has_multiple_threads);
+ if (has_multiple_threads > 1)
+ error (_("checkpoint: can't checkpoint multiple threads."));
+
/* Make the inferior fork, record its (and gdb's) state. */

if (lookup_minimal_symbol ("fork", NULL, NULL) != NULL)