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c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1757527508; 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=CdBgoYxIvUWgwyeZLw6CowPy0PcFEK/INVG0xv0t5KE=; b=FV8LdrWQk8iyRulrFNhqmsWRuE4lHYTZeRMJg4+kmdbKisFZrck5v+uVkPeVUuxDJ7E9Gd q5Zpnxvo2boQTcaWWVtlwQO6PCRFTzzaRGEBxT+fxUq9DwwYKkGxdnQudvqzyydo9Yx2Rg zEu/NJwOkVYfLBV4GM0djxDXcXQzR5g= X-MC-Unique: MZPVpweVMH20HsRhSFIDOg-1 X-Mimecast-MFC-AGG-ID: MZPVpweVMH20HsRhSFIDOg_1757527503 From: =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= To: qemu-devel@nongnu.org Cc: qemu-block@nongnu.org, Hanna Reitz , Kevin Wolf , =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= , Christian Schoenebeck , Richard Henderson , Manos Pitsidianakis , Stefan Weil , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= , Gerd Hoffmann , Paolo Bonzini , Markus Armbruster , "Dr. David Alan Gilbert" , =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= Subject: [PATCH v3 14/20] util: fix interleaving of error & trace output Date: Wed, 10 Sep 2025 19:03:51 +0100 Message-ID: <20250910180357.320297-15-berrange@redhat.com> In-Reply-To: <20250910180357.320297-1-berrange@redhat.com> References: <20250910180357.320297-1-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 10.30.177.93 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_H5=0.001, RCVD_IN_MSPIKE_WL=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=unavailable 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+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1757527621944116600 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_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 a decision about whether output will go to monitor_[v]printf() or fprintf() must be made upfront, and then those functions called directly. $ 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 This change requires adding a stub for monitor_printf() since that is now called directly by vreport(), where monitor_vprintf() was only needed previously. Signed-off-by: Daniel P. Berrang=C3=A9 Reviewed-by: Richard Henderson --- stubs/monitor-core.c | 5 +++ tests/unit/test-util-sockets.c | 1 + util/error-report.c | 60 ++++++++++++++++++++++++---------- 3 files changed, 48 insertions(+), 18 deletions(-) diff --git a/stubs/monitor-core.c b/stubs/monitor-core.c index 1e0b11ec29..70b1f7a994 100644 --- a/stubs/monitor-core.c +++ b/stubs/monitor-core.c @@ -30,3 +30,8 @@ int monitor_vprintf(Monitor *mon, const char *fmt, va_lis= t ap) { abort(); } + +int monitor_printf(Monitor *mon, const char *fmt, ...) +{ + abort(); +} diff --git a/tests/unit/test-util-sockets.c b/tests/unit/test-util-sockets.c index d40813c682..53733163dd 100644 --- a/tests/unit/test-util-sockets.c +++ b/tests/unit/test-util-sockets.c @@ -76,6 +76,7 @@ Monitor *monitor_cur_hmp(void) { return cur_mon; } bool monitor_cur_is_qmp(void) { return false; } Monitor *monitor_set_cur(Coroutine *co, Monitor *mon) { abort(); } int monitor_vprintf(Monitor *mon, const char *fmt, va_list ap) { abort(); } +int monitor_printf(Monitor *mon, const char *fmt, ...) { abort(); } =20 #ifndef _WIN32 static void test_socket_fd_pass_name_good(void) diff --git a/util/error-report.c b/util/error-report.c index c0fcf388de..6c887047e3 100644 --- a/util/error-report.c +++ b/util/error-report.c @@ -29,6 +29,9 @@ bool message_with_timestamp; bool error_with_guestname; const char *error_guest_name; =20 +typedef void (*error_print_func)(void *opaque, const char *fmt, ...); +typedef void (*error_print_vfunc)(void *opaque, const char *fmt, va_list a= p); + /* * Print to current monitor if we have one, else to stderr. */ @@ -151,34 +154,34 @@ 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(bool cur, error_print_func print_func, void *print_o= paque) { const char *sep =3D ""; int i; const char *const *argp; =20 - if (!monitor_cur_hmp() && g_get_prgname()) { - error_printf("%s:", g_get_prgname()); + if (!cur && g_get_prgname()) { + print_func(print_opaque, "%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]); + print_func(print_opaque, "%s%s", sep, argp[i]); sep =3D " "; } - error_printf(": "); + print_func(print_opaque, ": "); break; case LOC_FILE: - error_printf("%s:", (const char *)cur_loc->ptr); + print_func(print_opaque, "%s:", (const char *)cur_loc->ptr); if (cur_loc->num) { - error_printf("%d:", cur_loc->num); + print_func(print_opaque, "%d:", cur_loc->num); } - error_printf(" "); + print_func(print_opaque, " "); break; default: - error_printf("%s", sep); + print_func(print_opaque, "%s", sep); } } =20 @@ -199,34 +202,55 @@ real_time_iso8601(void) G_GNUC_PRINTF(2, 0) static void vreport(report_type type, const char *fmt, va_list ap) { + /* + * Calling monitor_cur_hmp() will acquire/release mutexes, + * which triggers trace probes, which can trigger + * qemu_log calls, which would interleave with output + * from this. Hence cache the monitor handle upfront + * so any tracing appears before we start outputting. + */ + Monitor *cur =3D monitor_cur_hmp(); + error_print_func print_func; + error_print_vfunc print_vfunc; + void *print_opaque; gchar *timestr; =20 - if (message_with_timestamp && !monitor_cur_hmp()) { + if (cur) { + print_func =3D (error_print_func)monitor_printf; + print_vfunc =3D (error_print_vfunc)monitor_vprintf; + print_opaque =3D cur; + } else { + print_func =3D (error_print_func)fprintf; + print_vfunc =3D (error_print_vfunc)vfprintf; + print_opaque =3D stderr; + } + + if (message_with_timestamp && !cur) { timestr =3D real_time_iso8601(); - error_printf("%s ", timestr); + print_func(print_opaque, "%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_hmp()) { - error_printf("%s ", error_guest_name); + if (error_with_guestname && error_guest_name && !cur) { + print_func(print_opaque, "%s ", error_guest_name); } =20 - print_loc(); + print_loc(!!cur, print_func, print_opaque); =20 switch (type) { case REPORT_TYPE_ERROR: break; case REPORT_TYPE_WARNING: - error_printf("warning: "); + print_func(print_opaque, "warning: "); break; case REPORT_TYPE_INFO: - error_printf("info: "); + print_func(print_opaque, "info: "); break; } =20 - error_vprintf(fmt, ap); - error_printf("\n"); + print_vfunc(print_opaque, fmt, ap); + print_func(print_opaque, "\n"); } =20 /* --=20 2.50.1