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Fri, 19 Sep 2025 08:23:12 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.45.242.33]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id A7EBB30002C5; Fri, 19 Sep 2025 08:23:11 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id E536921E6A27; Fri, 19 Sep 2025 10:23:08 +0200 (CEST) Resent-To: qemu_oss@crudebyte.com, manos.pitsidianakis@linaro.org, philmd@linaro.org, richard.henderson@linaro.org, qemu-block@nongnu.org, qemu-devel@nongnu.org, dave@treblig.org, sw@weilnetz.de Resent-From: Markus Armbruster Resent-Date: Fri, 19 Sep 2025 10:23:08 +0200 Resent-Message-ID: <87ms6q6ec3.fsf@pond.sub.org> From: Markus Armbruster To: Daniel P. =?utf-8?Q?Berrang=C3=A9?= Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org, Hanna Reitz , Kevin Wolf , =?utf-8?Q?Marc-Andr?= =?utf-8?Q?=C3=A9?= Lureau , Christian Schoenebeck , Richard Henderson , Manos Pitsidianakis , Stefan Weil , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Gerd Hoffmann , Paolo Bonzini , "Dr. David Alan Gilbert" Subject: Re: [PATCH v3 03/20] system: unconditionally enable thread naming In-Reply-To: <20250910180357.320297-4-berrange@redhat.com> ("Daniel P. =?utf-8?Q?Berrang=C3=A9=22's?= message of "Wed, 10 Sep 2025 19:03:40 +0100") References: <20250910180357.320297-1-berrange@redhat.com> <20250910180357.320297-4-berrange@redhat.com> Date: Fri, 19 Sep 2025 10:20:51 +0200 Message-ID: <87zfaq6efw.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.005, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Daniel P. Berrang=C3=A9 writes: > When thread naming was introduced years ago, it was disabled by > default and put behind a command line flag: > > commit 8f480de0c91a18d550721f8d9af969ebfbda0793 > Author: Dr. David Alan Gilbert > Date: Thu Jan 30 10:20:31 2014 +0000 > > Add 'debug-threads' suboption to --name > > This was done based on a concern that something might depend > on the historical thread naming. Thread names, however, were > never promised to be part of QEMU's public API. The defaults > will vary across platforms, so no assumptions should ever be > made about naming. > > An opt-in behaviour is also unfortunately incompatible with > RCU which creates its thread from an constructor function > which is run before command line args are parsed. Thus the > RCU thread lacks any name. > > libvirt has unconditionally enabled debug-threads=3Dyes on all > VMs it creates for 10 years. Interestingly this DID expose a > bug in libvirt, as it parsed /proc/$PID/stat and could not > cope with a space in the thread name. This was a latent > pre-existing bug in libvirt though, and not a part of QEMU's > API. > > Having thread names always available, will allow thread names > to be included in error reports and log messags QEMU prints > by default, which will improve ability to triage QEMU bugs. > > Reviewed-by: Dr. David Alan Gilbert > Reviewed-by: Richard Henderson > Signed-off-by: Daniel P. Berrang=C3=A9 > --- > docs/about/deprecated.rst | 7 +++++++ > include/qemu/thread.h | 1 - > system/vl.c | 11 ++++++----- > util/qemu-thread-posix.c | 18 +----------------- > util/qemu-thread-win32.c | 27 ++++++--------------------- > 5 files changed, 20 insertions(+), 44 deletions(-) > > diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst > index b2420732e1..7187ea15fa 100644 > --- a/docs/about/deprecated.rst > +++ b/docs/about/deprecated.rst > @@ -81,6 +81,13 @@ kernel since 2001. None of the board types QEMU suppor= ts need > ``param_struct`` support, so this option has been deprecated and will > be removed in a future QEMU version. >=20=20 > +``debug-threads`` option for ``-name`` > +'''''''''''''''''''''''''''''''''''''' > + > +Thread ``debug-threads`` option for the ``-name`` argument is now Do you mean "The ``debug-threads`` option"? "option for" or "option of"? Not a native speaker... > +ignored. Thread naming is unconditionally enabled for all platforms > +where it is supported. > + > QEMU Machine Protocol (QMP) commands > ------------------------------------ >=20=20 > diff --git a/include/qemu/thread.h b/include/qemu/thread.h > index f0302ed01f..3a286bb3ef 100644 > --- a/include/qemu/thread.h > +++ b/include/qemu/thread.h > @@ -215,7 +215,6 @@ void *qemu_thread_join(QemuThread *thread); > void qemu_thread_get_self(QemuThread *thread); > bool qemu_thread_is_self(QemuThread *thread); > G_NORETURN void qemu_thread_exit(void *retval); > -void qemu_thread_naming(bool enable); >=20=20 > struct Notifier; > /** > diff --git a/system/vl.c b/system/vl.c > index 3b7057e6c6..a64fd90d4a 100644 > --- a/system/vl.c > +++ b/system/vl.c > @@ -403,9 +403,7 @@ static QemuOptsList qemu_name_opts =3D { > }, { > .name =3D "debug-threads", > .type =3D QEMU_OPT_BOOL, > - .help =3D "When enabled, name the individual threads; defaul= ts off.\n" > - "NOTE: The thread names are for debugging and not a\= n" > - "stable API.", > + .help =3D "DEPRECATED: thread names are always set where sup= ported", Please don't shout :) We rarely note deprecation notes in command line help texts. I found two. block/qcow.c: { .name =3D BLOCK_OPT_ENCRYPT, .type =3D QEMU_OPT_BOOL, .help =3D "Encrypt the image with format 'aes'. (Deprecated " "in favor of " BLOCK_OPT_ENCRYPT_FORMAT "=3Daes)", }, block/qcow2.c: { \ .name =3D BLOCK_OPT_ENCRYPT, \ .type =3D QEMU_OPT_BOOL, \ .help =3D "Encrypt the image with format 'aes'. (Deprecated " \ "in favor of " BLOCK_OPT_ENCRYPT_FORMAT "=3Daes)", \ }, \ { \ Suggest something like .help =3D "Enable thread names" " (deprecated, always enabled where supported)", > }, > { /* End of list */ } > }, > @@ -554,9 +552,12 @@ static int parse_name(void *opaque, QemuOpts *opts, = Error **errp) > { > const char *proc_name; >=20=20 > - if (qemu_opt_get(opts, "debug-threads")) { > - qemu_thread_naming(qemu_opt_get_bool(opts, "debug-threads", fals= e)); > + if (qemu_opt_get(opts, "debug-threads") && > + !qemu_opt_get_bool(opts, "debug-threads", false)) { > + fprintf(stderr, "Ignoring deprecated 'debug-threads=3Dno' option= , " \ > + "thread naming is unconditionally enabled\n"); Not sure this is worth the trouble, but since you wrote and tested it already... > } > + > qemu_name =3D qemu_opt_get(opts, "guest"); >=20=20 > proc_name =3D qemu_opt_get(opts, "process"); > diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c > index ba725444ba..7c985b5d38 100644 > --- a/util/qemu-thread-posix.c > +++ b/util/qemu-thread-posix.c > @@ -22,22 +22,6 @@ > #include > #endif >=20=20 > -static bool name_threads; > - > -void qemu_thread_naming(bool enable) > -{ > - name_threads =3D enable; > - > -#if !defined CONFIG_PTHREAD_SETNAME_NP_W_TID && \ > - !defined CONFIG_PTHREAD_SETNAME_NP_WO_TID && \ > - !defined CONFIG_PTHREAD_SET_NAME_NP > - /* This is a debugging option, not fatal */ > - if (enable) { > - fprintf(stderr, "qemu: thread naming not supported on this host\= n"); > - } > -#endif > -} > - > static void error_exit(int err, const char *msg) > { > fprintf(stderr, "qemu: %s: %s\n", msg, strerror(err)); > @@ -361,7 +345,7 @@ static void *qemu_thread_start(void *args) > /* Attempt to set the threads name; note that this is for debug, so > * we're not going to fail if we can't set it. > */ > - if (name_threads && qemu_thread_args->name) { > + if (qemu_thread_args->name) { > # if defined(CONFIG_PTHREAD_SETNAME_NP_W_TID) > pthread_setname_np(pthread_self(), qemu_thread_args->name); > # elif defined(CONFIG_PTHREAD_SETNAME_NP_WO_TID) > diff --git a/util/qemu-thread-win32.c b/util/qemu-thread-win32.c > index ca2e0b512e..9595a5b090 100644 > --- a/util/qemu-thread-win32.c > +++ b/util/qemu-thread-win32.c > @@ -17,8 +17,6 @@ > #include "qemu-thread-common.h" > #include >=20=20 > -static bool name_threads; > - > typedef HRESULT (WINAPI *pSetThreadDescription) (HANDLE hThread, > PCWSTR lpThreadDescript= ion); > static pSetThreadDescription SetThreadDescriptionFunc; > @@ -44,16 +42,6 @@ static bool load_set_thread_description(void) > return !!SetThreadDescriptionFunc; > } >=20=20 > -void qemu_thread_naming(bool enable) > -{ > - name_threads =3D enable; > - > - if (enable && !load_set_thread_description()) { > - fprintf(stderr, "qemu: thread naming not supported on this host\= n"); > - name_threads =3D false; > - } > -} > - > static void error_exit(int err, const char *msg) > { > char *pstr; > @@ -328,23 +316,20 @@ void *qemu_thread_join(QemuThread *thread) > return ret; > } >=20=20 > -static bool set_thread_description(HANDLE h, const char *name) > +static void set_thread_description(HANDLE h, const char *name) > { > - HRESULT hr; > g_autofree wchar_t *namew =3D NULL; >=20=20 > if (!load_set_thread_description()) { > - return false; > + return; > } >=20=20 > namew =3D g_utf8_to_utf16(name, -1, NULL, NULL, NULL); > if (!namew) { > - return false; > + return; > } >=20=20 > - hr =3D SetThreadDescriptionFunc(h, namew); > - > - return SUCCEEDED(hr); > + SetThreadDescriptionFunc(h, namew); > } >=20=20 > void qemu_thread_create(QemuThread *thread, const char *name, > @@ -370,8 +355,8 @@ void qemu_thread_create(QemuThread *thread, const cha= r *name, > if (!hThread) { > error_exit(GetLastError(), __func__); > } > - if (name_threads && name && !set_thread_description(hThread, name)) { > - fprintf(stderr, "qemu: failed to set thread description: %s\n", = name); > + if (name) { > + set_thread_description(hThread, name); > } > CloseHandle(hThread); Modulo nits: Reviewed-by: Markus Armbruster