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c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1770823632; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=RAw0M5DQrWvr04qhs1mJQ/D6Qx2tWsXmBnfqMP/fRAg=; b=VclvwwfBDjvsU4OXByDEnODhG4UJgiaaynlsj/jWEZlUTpJjIP7GbYj/vaZM6JkrDx5b2O RXexJ2PSCus7S1P4IsVDxh7U7OxdNf8JGgFGjb9aRGMM+AmozSf5w7H0/aL8TC2D+MfWuc ARVbgCR7fmbEJfeY1nF05t/nkRNzcWc= X-MC-Unique: s9KGedNhOS2bf2mYapvZ5A-1 X-Mimecast-MFC-AGG-ID: s9KGedNhOS2bf2mYapvZ5A_1770823624 From: =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= To: qemu-devel@nongnu.org Cc: Manos Pitsidianakis , Stefan Weil , "Dr. David Alan Gilbert" , Pierrick Bouvier , devel@lists.libvirt.org, =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= , =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= , Hanna Reitz , Kevin Wolf , qemu-block@nongnu.org, qemu-rust@nongnu.org, Paolo Bonzini , Markus Armbruster , Gerd Hoffmann , =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= , Christian Schoenebeck , Richard Henderson Subject: [PATCH v6 19/27] util: fix interleaving of error & trace output Date: Wed, 11 Feb 2026 15:25:00 +0000 Message-ID: <20260211152508.732487-20-berrange@redhat.com> In-Reply-To: <20260211152508.732487-1-berrange@redhat.com> References: <20260211152508.732487-1-berrange@redhat.com> 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 (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@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=-0.001, 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_H2=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_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: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1770823913344158500 The monitor_cur_hmp() function will acquire/release mutex locks, which will trigger trace probes, which can in turn trigger qemu_log() calls. vreport() calls monitor_cur() multiple times through its execution both directly and indirectly via error_vprintf(). The result is that the prefix information printed by vreport() gets interleaved with qemu_log() output, when run outside the context of an HMP command dispatcher. This can be seen with: $ qemu-system-x86_64 \ -msg timestamp=3Don,guest-name=3Don \ -display none \ -object tls-creds-x509,id=3Df,dir=3Dfish \ -name fish \ -d trace:qemu_mutex* 2025-09-10T16:30:42.514374Z qemu_mutex_unlock released mutex 0x560b0339b= 4c0 (/var/home/berrange/src/virt/qemu/include/qemu/lockable.h:56) 2025-09-10T16:30:42.514400Z qemu_mutex_lock waiting on mutex 0x560b03398= 3e0 (/var/home/berrange/src/virt/qemu/include/qemu/lockable.h:56) 2025-09-10T16:30:42.514402Z qemu_mutex_locked taken mutex 0x560b033983e0= (/var/home/berrange/src/virt/qemu/include/qemu/lockable.h:56) 2025-09-10T16:30:42.514404Z qemu_mutex_unlock released mutex 0x560b03398= 3e0 (/var/home/berrange/src/virt/qemu/include/qemu/lockable.h:56) 2025-09-10T16:30:42.516716Z qemu_mutex_lock waiting on mutex 0x560b03398= 560 (../monitor/monitor.c:91) 2025-09-10T16:30:42.516723Z qemu_mutex_locked taken mutex 0x560b03398560= (../monitor/monitor.c:91) 2025-09-10T16:30:42.516726Z qemu_mutex_unlock released mutex 0x560b03398= 560 (../monitor/monitor.c:96) 2025-09-10T16:30:42.516728Z qemu_mutex_lock waiting on mutex 0x560b03398= 560 (../monitor/monitor.c:91) 2025-09-10T16:31:04.842057Z qemu_mutex_locked taken mutex 0x564f5e401560= (../monitor/monitor.c:91) 2025-09-10T16:31:04.842058Z qemu_mutex_unlock released mutex 0x564f5e401= 560 (../monitor/monitor.c:96) 2025-09-10T16:31:04.842055Z 2025-09-10T16:31:04.842060Z qemu_mutex_lock = waiting on mutex 0x564f5e401560 (../monitor/monitor.c:91) 2025-09-10T16:31:04.842061Z qemu_mutex_locked taken mutex 0x564f5e401560= (../monitor/monitor.c:91) 2025-09-10T16:31:04.842062Z qemu_mutex_unlock released mutex 0x564f5e401= 560 (../monitor/monitor.c:96) 2025-09-10T16:31:04.842064Z qemu_mutex_lock waiting on mutex 0x564f5e401= 560 (../monitor/monitor.c:91) 2025-09-10T16:31:04.842065Z qemu_mutex_locked taken mutex 0x564f5e401560= (../monitor/monitor.c:91) 2025-09-10T16:31:04.842066Z qemu_mutex_unlock released mutex 0x564f5e401= 560 (../monitor/monitor.c:96) fish 2025-09-10T16:31:04.842068Z qemu_mutex_lock waiting on mutex 0x564f= 5e401560 (../monitor/monitor.c:91) 2025-09-10T16:31:04.842069Z qemu_mutex_locked taken mutex 0x564f5e401560= (../monitor/monitor.c:91) 2025-09-10T16:31:04.842070Z qemu_mutex_unlock released mutex 0x564f5e401= 560 (../monitor/monitor.c:96) 2025-09-10T16:31:04.842072Z qemu_mutex_lock waiting on mutex 0x564f5e401= 560 (../monitor/monitor.c:91) 2025-09-10T16:31:04.842097Z qemu_mutex_locked taken mutex 0x564f5e401560= (../monitor/monitor.c:91) 2025-09-10T16:31:04.842099Z qemu_mutex_unlock released mutex 0x564f5e401= 560 (../monitor/monitor.c:96) qemu-system-x86_64:2025-09-10T16:31:04.842100Z qemu_mutex_lock waiting o= n mutex 0x564f5e401560 (../monitor/monitor.c:91) 2025-09-10T16:31:04.842102Z qemu_mutex_locked taken mutex 0x564f5e401560= (../monitor/monitor.c:91) 2025-09-10T16:31:04.842103Z qemu_mutex_unlock released mutex 0x564f5e401= 560 (../monitor/monitor.c:96) 2025-09-10T16:31:04.842105Z qemu_mutex_lock waiting on mutex 0x564f5e40= 1560 (../monitor/monitor.c:91) 2025-09-10T16:31:04.842106Z qemu_mutex_locked taken mutex 0x564f5e401560= (../monitor/monitor.c:91) 2025-09-10T16:31:04.842107Z qemu_mutex_unlock released mutex 0x564f5e401= 560 (../monitor/monitor.c:96) Unable to access credentials fish/ca-cert.pem: No such file or directory= 2025-09-10T16:31:04.842109Z qemu_mutex_lock waiting on mutex 0x564f5e401560= (../monitor/monitor.c:91) 2025-09-10T16:31:04.842110Z qemu_mutex_locked taken mutex 0x564f5e401560= (../monitor/monitor.c:91) 2025-09-10T16:31:04.842111Z qemu_mutex_unlock released mutex 0x564f5e401= 560 (../monitor/monitor.c:96) To avoid this interleaving (as well as reduce the huge number of mutex lock/unlock calls) we need to ensure that monitor_cur_is_hmp() is only called once at the start of vreport(), and if no HMP is present, no further monitor APIs can be called. This implies error_[v]printf() cannot be called from vreport(). Instead we must introduce error_[v]printf_mon() which accept a pre-acquired Monitor object. In some cases, however, fprintf can be called directly as output will never be directed to the monitor. $ qemu-system-x86_64 \ -msg timestamp=3Don,guest-name=3Don \ -display none \ -object tls-creds-x509,id=3Df,dir=3Dfish \ -name fish \ -d trace:qemu_mutex* 2025-09-10T16:31:22.701691Z qemu_mutex_unlock released mutex 0x5626fd3b8= 4c0 (/var/home/berrange/src/virt/qemu/include/qemu/lockable.h:56) 2025-09-10T16:31:22.701728Z qemu_mutex_lock waiting on mutex 0x5626fd3b5= 3e0 (/var/home/berrange/src/virt/qemu/include/qemu/lockable.h:56) 2025-09-10T16:31:22.701730Z qemu_mutex_locked taken mutex 0x5626fd3b53e0= (/var/home/berrange/src/virt/qemu/include/qemu/lockable.h:56) 2025-09-10T16:31:22.701732Z qemu_mutex_unlock released mutex 0x5626fd3b5= 3e0 (/var/home/berrange/src/virt/qemu/include/qemu/lockable.h:56) 2025-09-10T16:31:22.703989Z qemu_mutex_lock waiting on mutex 0x5626fd3b5= 560 (../monitor/monitor.c:91) 2025-09-10T16:31:22.703996Z qemu_mutex_locked taken mutex 0x5626fd3b5560= (../monitor/monitor.c:91) 2025-09-10T16:31:22.703999Z qemu_mutex_unlock released mutex 0x5626fd3b5= 560 (../monitor/monitor.c:96) 2025-09-10T16:31:22.704000Z fish qemu-system-x86_64: Unable to access cr= edentials fish/ca-cert.pem: No such file or directory Reviewed-by: Richard Henderson Signed-off-by: Daniel P. Berrang=C3=A9 --- util/error-report.c | 63 ++++++++++++++++++++++++++++++--------------- 1 file changed, 42 insertions(+), 21 deletions(-) diff --git a/util/error-report.c b/util/error-report.c index f3aa24ec22..b34a2bc7bc 100644 --- a/util/error-report.c +++ b/util/error-report.c @@ -32,9 +32,9 @@ const char *error_guest_name; /* * Print to the current human monitor if we have one, else to stderr. */ -int error_vprintf(const char *fmt, va_list ap) +static int G_GNUC_PRINTF(2, 0) +error_vprintf_mon(Monitor *cur_mon, const char *fmt, va_list ap) { - Monitor *cur_mon =3D monitor_cur(); /* * This will return -1 if 'cur_mon' is NULL, or is QMP. * IOW this will only print if in HMP, otherwise we @@ -47,13 +47,33 @@ int error_vprintf(const char *fmt, va_list ap) return ret; } =20 +/* + * Print to the current human monitor if we have one, else to stderr. + */ +static int G_GNUC_PRINTF(2, 3) +error_printf_mon(Monitor *cur_mon, const char *fmt, ...) +{ + va_list ap; + int ret; + + va_start(ap, fmt); + ret =3D error_vprintf_mon(cur_mon, fmt, ap); + va_end(ap); + return ret; +} + +int error_vprintf(const char *fmt, va_list ap) +{ + return error_vprintf_mon(monitor_cur(), fmt, ap); +} + int error_printf(const char *fmt, ...) { va_list ap; int ret; =20 va_start(ap, fmt); - ret =3D error_vprintf(fmt, ap); + ret =3D error_vprintf_mon(monitor_cur(), fmt, ap); va_end(ap); return ret; } @@ -156,34 +176,34 @@ void loc_set_file(const char *fname, int lno) /* * Print current location to current monitor if we have one, else to stder= r. */ -static void print_loc(void) +static void print_loc(Monitor *cur) { const char *sep =3D ""; int i; const char *const *argp; =20 - if (!monitor_cur() && g_get_prgname()) { - error_printf("%s:", g_get_prgname()); + if (!cur && g_get_prgname()) { + fprintf(stderr, "%s:", g_get_prgname()); sep =3D " "; } switch (cur_loc->kind) { case LOC_CMDLINE: argp =3D cur_loc->ptr; for (i =3D 0; i < cur_loc->num; i++) { - error_printf("%s%s", sep, argp[i]); + error_printf_mon(cur, "%s%s", sep, argp[i]); sep =3D " "; } - error_printf(": "); + error_printf_mon(cur, ": "); break; case LOC_FILE: - error_printf("%s:", (const char *)cur_loc->ptr); + error_printf_mon(cur, "%s:", (const char *)cur_loc->ptr); if (cur_loc->num) { - error_printf("%d:", cur_loc->num); + error_printf_mon(cur, "%d:", cur_loc->num); } - error_printf(" "); + error_printf_mon(cur, " "); break; default: - error_printf("%s", sep); + error_printf_mon(cur, "%s", sep); } } =20 @@ -204,34 +224,35 @@ real_time_iso8601(void) G_GNUC_PRINTF(2, 0) static void vreport(report_type type, const char *fmt, va_list ap) { + Monitor *cur =3D monitor_cur(); gchar *timestr; =20 - if (message_with_timestamp && !monitor_cur()) { + if (message_with_timestamp && !cur) { timestr =3D real_time_iso8601(); - error_printf("%s ", timestr); + fprintf(stderr, "%s ", timestr); g_free(timestr); } =20 /* Only prepend guest name if -msg guest-name and -name guest=3D... ar= e set */ - if (error_with_guestname && error_guest_name && !monitor_cur()) { - error_printf("%s ", error_guest_name); + if (error_with_guestname && error_guest_name && !cur) { + fprintf(stderr, "%s ", error_guest_name); } =20 - print_loc(); + print_loc(cur); =20 switch (type) { case REPORT_TYPE_ERROR: break; case REPORT_TYPE_WARNING: - error_printf("warning: "); + error_printf_mon(cur, "warning: "); break; case REPORT_TYPE_INFO: - error_printf("info: "); + error_printf_mon(cur, "info: "); break; } =20 - error_vprintf(fmt, ap); - error_printf("\n"); + error_vprintf_mon(cur, fmt, ap); + error_printf_mon(cur, "\n"); } =20 /* --=20 2.53.0