* Daniel P. Berrangé (berrange@redhat.com) wrote:
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 <dgilbert@redhat.com> 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.
Ah finally! Reviewed-by: Dr. David Alan Gilbert <dave@treblig.org>
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=yes 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.
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com> --- 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 d50645a071..bd6f865558 100644 --- a/docs/about/deprecated.rst +++ b/docs/about/deprecated.rst @@ -81,6 +81,13 @@ kernel since 2001. None of the board types QEMU supports need ``param_struct`` support, so this option has been deprecated and will be removed in a future QEMU version.
+``debug-threads`` option for ``-name`` +'''''''''''''''''''''''''''''''''''''' + +Thread ``debug-threads`` option for the ``-name`` argument is now +ignored. Thread naming is unconditionally enabled for all platforms +where it is supported. + User-mode emulator command line arguments -----------------------------------------
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);
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 = { }, { .name = "debug-threads", .type = QEMU_OPT_BOOL, - .help = "When enabled, name the individual threads; defaults off.\n" - "NOTE: The thread names are for debugging and not a\n" - "stable API.", + .help = "DEPRECATED: thread names are always set where supported", }, { /* End of list */ } }, @@ -554,9 +552,12 @@ static int parse_name(void *opaque, QemuOpts *opts, Error **errp) { const char *proc_name;
- if (qemu_opt_get(opts, "debug-threads")) { - qemu_thread_naming(qemu_opt_get_bool(opts, "debug-threads", false)); + if (qemu_opt_get(opts, "debug-threads") && + !qemu_opt_get_bool(opts, "debug-threads", false)) { + fprintf(stderr, "Ignoring deprecated 'debug-threads=no' option, " \ + "thread naming is unconditionally enabled\n"); } + qemu_name = qemu_opt_get(opts, "guest");
proc_name = 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 <pthread_np.h> #endif
-static bool name_threads; - -void qemu_thread_naming(bool enable) -{ - name_threads = 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 <process.h>
-static bool name_threads; - typedef HRESULT (WINAPI *pSetThreadDescription) (HANDLE hThread, PCWSTR lpThreadDescription); static pSetThreadDescription SetThreadDescriptionFunc; @@ -44,16 +42,6 @@ static bool load_set_thread_description(void) return !!SetThreadDescriptionFunc; }
-void qemu_thread_naming(bool enable) -{ - name_threads = enable; - - if (enable && !load_set_thread_description()) { - fprintf(stderr, "qemu: thread naming not supported on this host\n"); - name_threads = false; - } -} - static void error_exit(int err, const char *msg) { char *pstr; @@ -328,23 +316,20 @@ void *qemu_thread_join(QemuThread *thread) return ret; }
-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 = NULL;
if (!load_set_thread_description()) { - return false; + return; }
namew = g_utf8_to_utf16(name, -1, NULL, NULL, NULL); if (!namew) { - return false; + return; }
- hr = SetThreadDescriptionFunc(h, namew); - - return SUCCEEDED(hr); + SetThreadDescriptionFunc(h, namew); }
void qemu_thread_create(QemuThread *thread, const char *name, @@ -370,8 +355,8 @@ void qemu_thread_create(QemuThread *thread, const char *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);
-- 2.50.1
-- -----Open up your eyes, open up your mind, open up your code ------- / Dr. David Alan Gilbert | Running GNU/Linux | Happy \ \ dave @ treblig.org | | In Hex / \ _________________________|_____ http://www.treblig.org |_______/