Re: [PATCH 02/31] linux-nat: introduce pending_status_str

Andrew Burgess via Gdb-patches
2023-03-16T16:20:08Z

Pedro Alves <pedro@palves.net> writes:

> On 2023-02-03 12:00 p.m., Andrew Burgess wrote:
>> Pedro Alves <pedro@palves.net> writes:
>>
>>> I noticed that some debug log output printing an lwp's pending status
>>> wasn't considering lp->waitstatus. This fixes it, by introducing a
>>> new pending_status_str function.
>>
>> This patch looks fine. I had one slightly related question: I took a
>> look at the comment on lwp_info::waitstatus in linux-nat.h, which says:
>>
>> /* If WAITSTATUS->KIND != TARGET_WAITKIND_SPURIOUS, the waitstatus
>> for this LWP's last event. This may correspond to STATUS above,
>> or to a local variable in lin_lwp_wait. */
>> struct target_waitstatus waitstatus;
>>
>> Am I right in thinking that this comment is wrong; it should say
>> TARGET_WAITKIND_IGNORE, not TARGET_WAITKIND_SPURIOUS, right?
>
> You're right.
>
> I tweaked the comments in linux-nat.h in this new version. Let me know what
> you think.
>
> From 10f88baff2e25fb87f37d1665bf283206171dd42 Mon Sep 17 00:00:00 2001
> From: Pedro Alves <pedro@palves.net>
> Date: Fri, 12 Nov 2021 20:50:29 +0000
> Subject: [PATCH] linux-nat: introduce pending_status_str
>
> I noticed that some debug log output printing an lwp's pending status
> wasn't considering lp->waitstatus. This fixes it, by introducing a
> new pending_status_str function.
>
> Also fix the comment in gdb/linux-nat.h describing
> lwp_info::waitstatus and details the description of lwp_info::status
> while at it.
>
> Change-Id: I66e5c7a363d30a925b093b195d72925ce5b6b980
> ---
> gdb/linux-nat.c | 19 ++++++++++++++++---
> gdb/linux-nat.h | 11 +++++++----
> 2 files changed, 23 insertions(+), 7 deletions(-)

LGTM.

Reviewed-By: Andrew Burgess <aburgess@redhat.com>

Thanks,
Andrew

>
> diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
> index e5391b9ce35..9d811bbf3ff 100644
> --- a/gdb/linux-nat.c
> +++ b/gdb/linux-nat.c
> @@ -255,6 +255,19 @@ is_leader (lwp_info *lp)
> return lp->ptid.pid () == lp->ptid.lwp ();
> }
>
> +/* Convert an LWP's pending status to a std::string. */
> +
> +static std::string
> +pending_status_str (lwp_info *lp)
> +{
> + gdb_assert (lwp_status_pending_p (lp));
> +
> + if (lp->waitstatus.kind () != TARGET_WAITKIND_IGNORE)
> + return lp->waitstatus.to_string ();
> + else
> + return status_to_str (lp->status);
> +}
> +
> \f
> /* LWP accessors. */
>
> @@ -1647,8 +1660,8 @@ linux_nat_target::resume (ptid_t scope_ptid, int step, enum gdb_signal signo)
> this thread with a signal? */
> gdb_assert (signo == GDB_SIGNAL_0);
>
> - linux_nat_debug_printf ("Short circuiting for status 0x%x",
> - lp->status);
> + linux_nat_debug_printf ("Short circuiting for status %s",
> + pending_status_str (lp).c_str ());
>
> if (target_can_async_p ())
> {
> @@ -3137,7 +3150,7 @@ linux_nat_wait_1 (ptid_t ptid, struct target_waitstatus *ourstatus,
> if (lp != NULL)
> {
> linux_nat_debug_printf ("Using pending wait status %s for %s.",
> - status_to_str (lp->status).c_str (),
> + pending_status_str (lp).c_str (),
> lp->ptid.to_string ().c_str ());
> }
>
> diff --git a/gdb/linux-nat.h b/gdb/linux-nat.h
> index 45534c92386..770fe924427 100644
> --- a/gdb/linux-nat.h
> +++ b/gdb/linux-nat.h
> @@ -232,7 +232,9 @@ struct lwp_info : intrusive_list_node<lwp_info>
> /* The last resume GDB requested on this thread. */
> resume_kind last_resume_kind = resume_continue;
>
> - /* If non-zero, a pending wait status. */
> + /* If non-zero, a pending wait status. A pending process exit is
> + recorded in WAITSTATUS, because W_EXITCODE(0,0) happens to be
> + 0. */
> int status = 0;
>
> /* When 'stopped' is set, this is where the lwp last stopped, with
> @@ -260,9 +262,10 @@ struct lwp_info : intrusive_list_node<lwp_info>
> /* Non-zero if we expect a duplicated SIGINT. */
> int ignore_sigint = 0;
>
> - /* If WAITSTATUS->KIND != TARGET_WAITKIND_SPURIOUS, the waitstatus
> - for this LWP's last event. This may correspond to STATUS above,
> - or to a local variable in lin_lwp_wait. */
> + /* If WAITSTATUS->KIND != TARGET_WAITKIND_IGNORE, the waitstatus for
> + this LWP's last event. This usually corresponds to STATUS above,
> + however because W_EXITCODE(0,0) happens to be 0, a process exit
> + will be recorded here, while 'status == 0' is ambiguous. */
> struct target_waitstatus waitstatus;
>
> /* Signal whether we are in a SYSCALL_ENTRY or
>
> base-commit: 2562954ede66f32bff7d985e752b8052c2ae5775
> prerequisite-patch-id: bbc9918ac5f79de07a29f34ec072794d270f942d
> --
> 2.36.0