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Re: [PATCH v7 03/11] hw/core: create Resettable QOM interface

From: Philippe Mathieu-Daudé
Subject: Re: [PATCH v7 03/11] hw/core: create Resettable QOM interface
Date: Thu, 16 Jan 2020 09:57:45 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2

On 1/16/20 9:53 AM, Damien Hedde wrote:
On 1/16/20 2:59 AM, Philippe Mathieu-Daudé wrote:
On 1/15/20 1:36 PM, Damien Hedde wrote:
This commit defines an interface allowing multi-phase reset. This aims
to solve a problem of the actual single-phase reset (built in
DeviceClass and BusClass): reset behavior is dependent on the order
in which reset handlers are called. In particular doing external
side-effect (like setting an qemu_irq) is problematic because receiving
object may not be reset yet.

The Resettable interface divides the reset in 3 well defined phases.
To reset an object tree, all 1st phases are executed then all 2nd then
all 3rd. See the comments in include/hw/resettable.h for a more complete
description. The interface defines 3 phases to let the future
possibility of holding an object into reset for some time.

The qdev/qbus reset in DeviceClass and BusClass will be modified in
following commits to use this interface. A mechanism is provided
to allow executing a transitional reset handler in place of the 2nd
phase which is executed in children-then-parent order inside a tree.
This will allow to transition devices and buses smoothly while
keeping the exact current qdev/qbus reset behavior for now.

Documentation will be added in a following commit.

Signed-off-by: Damien Hedde <address@hidden>
Reviewed-by: Richard Henderson <address@hidden>

v7 update: un-nest struct ResettablePhases
   Makefile.objs           |   1 +
   include/hw/resettable.h | 211 +++++++++++++++++++++++++++++++++++
   hw/core/resettable.c    | 238 ++++++++++++++++++++++++++++++++++++++++
   hw/core/Makefile.objs   |   1 +
   hw/core/trace-events    |  17 +++
   5 files changed, 468 insertions(+)
   create mode 100644 include/hw/resettable.h
   create mode 100644 hw/core/resettable.c

Something here breaks ./configure --enable-trace-backends=ust:

   CC      trace-ust-all.o
In file included from trace-ust-all.h:13,
                  from trace-ust-all.c:13:
trace-ust-all.h:35151:1: error: redefinition of
       | ^~~~~~~~~~~~~~~~
trace-ust-all.h:31791:1: note: previous definition of
‘__tracepoint_cb_qemu___loader_write_rom’ was here
       | ^~~~~~~~~~~~~~~~
./trace-ust-all.h:35388:1: error: redefinition of
       | ^~~~~~~~~~~~~~~~
./trace-ust-all.h:32028:1: note: previous definition of
‘__tp_event_signature___qemu___resettable_transitional_function’ was here
       | ^~~~~~~~~~~~~~~~
In file included from /usr/include/lttng/tracepoint-event.h:58,
                  from trace-ust-all.h:35401,
                  from trace-ust-all.c:13:


32029    qemu,
32030    resettable_transitional_function,
32031    TP_ARGS(void *, obj, const char *, objtype),
32032    TP_FIELDS(
32033        ctf_integer_hex(void *, obj, obj)
32034        ctf_string(objtype, objtype)
32035    )
32036 )
35389    qemu,
35390    resettable_transitional_function,
35391    TP_ARGS(void *, obj, const char *, objtype),
35392    TP_FIELDS(
35393        ctf_integer_hex(void *, obj, obj)
35394        ctf_string(objtype, objtype)
35395    )
35396 )
35398 #endif /* TRACE_ALL_GENERATED_UST_H */

Ah! I was going to say "no clue what could be wrong, so Cc'ing Stefan"
but got it:

$ git grep hw/core Makefile.objs
Makefile.objs:194:trace-events-subdirs += hw/core
Makefile.objs:207:trace-events-subdirs += hw/core

We might already have a 'uniq' makefile function to do:

trace-events-subdirs = $(call uniq $(trace-events-subdirs))

or maybe was it with $filter? I can't find it/remember, too tired.

You can use $sort to remove duplicates in make.

Ah $(sort ...) thanks, I was too tired to remember it =)

So the fix is:

-- >8 --
--- a/Makefile.objs
+++ b/Makefile.objs
@@ -191,7 +191,6 @@ trace-events-subdirs += migration
  trace-events-subdirs += net
  trace-events-subdirs += ui
-trace-events-subdirs += hw/core
  trace-events-subdirs += hw/display
  trace-events-subdirs += qapi
  trace-events-subdirs += qom

I'll remove the duplicate entry.

I prepared a patch to move hw/core, if qemu-trivial merges it first, you shouldn't need to respin your series.

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