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Tue, 30 Jun 2020 13:28:48 +0000 (UTC) References: <20200626162706.3304357-1-dinechin@redhat.com> <20200626162706.3304357-3-dinechin@redhat.com> <20200630090556.GA2673@work-vm> User-agent: mu4e 1.5.2; emacs 26.3 From: Christophe de Dinechin To: "Dr. David Alan Gilbert" Subject: Re: [PATCH v2 2/3] trace: Add support for recorder back-end In-reply-to: <20200630090556.GA2673@work-vm> Date: Tue, 30 Jun 2020 15:28:46 +0200 Message-ID: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dinechin@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Received-SPF: pass client-ip=207.211.31.81; envelope-from=dinechin@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/30 02:00:02 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, 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_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Markus Armbruster , Michael Tokarev , qemu-devel@nongnu.org, Stefan Hajnoczi , Laurent Vivier Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 2020-06-30 at 11:05 CEST, Dr. David Alan Gilbert wrote... > * Christophe de Dinechin (dinechin@redhat.com) wrote: >> The recorder library provides support for low-cost continuous >> recording of events, which can then be replayed. This makes it >> possible to collect data "after the fact",for example to show the >> events that led to a crash. >> >> Recorder support in qemu is implemented using the existing tracing >> interface. In addition, it is possible to individually enable >> recorders that are not traces, although this is probably not >> recommended. >> >> HMP COMMAND: >> The 'recorder' hmp command has been added, which supports two >> sub-commands: >> - recorder dump: Dump the current state of the recorder. You can > ^^^^^^^^ > is that intended? No. I think the intent was to indicate that you could pass the name of a recorder to dump as an arg. I'll fix. > >> - recorder trace: Set traces using the recorder_trace_set() syntax. >> You can use "recorder trace help" to list all available recorders. >> >> Signed-off-by: Christophe de Dinechin >> --- >> configure | 5 +++ >> hmp-commands.hx | 19 ++++++++-- >> monitor/misc.c | 27 ++++++++++++++ >> scripts/tracetool/backend/recorder.py | 51 +++++++++++++++++++++++++++ >> trace/Makefile.objs | 2 ++ >> trace/control.c | 7 ++++ >> trace/recorder.c | 22 ++++++++++++ >> trace/recorder.h | 34 ++++++++++++++++++ >> util/module.c | 8 +++++ >> 9 files changed, 173 insertions(+), 2 deletions(-) >> create mode 100644 scripts/tracetool/backend/recorder.py >> create mode 100644 trace/recorder.c >> create mode 100644 trace/recorder.h >> >> diff --git a/configure b/configure >> index ae8737d5a2..130630b98f 100755 >> --- a/configure >> +++ b/configure >> @@ -7702,6 +7702,11 @@ fi >> if have_backend "log"; then >> echo "CONFIG_TRACE_LOG=y" >> $config_host_mak >> fi >> +if have_backend "recorder"; then >> + echo "CONFIG_TRACE_RECORDER=y" >> $config_host_mak >> + # This is a bit brutal, but there is currently a bug in the makefiles >> + LIBS="$LIBS -lrecorder" >> +fi >> if have_backend "ust"; then >> echo "CONFIG_TRACE_UST=y" >> $config_host_mak >> fi >> diff --git a/hmp-commands.hx b/hmp-commands.hx >> index 60f395c276..565f518d4b 100644 >> --- a/hmp-commands.hx >> +++ b/hmp-commands.hx >> @@ -297,6 +297,22 @@ ERST >> .cmd = hmp_trace_file, >> }, >> >> +SRST >> +``trace-file on|off|flush`` >> + Open, close, or flush the trace file. If no argument is given, the >> + status of the trace file is displayed. >> +ERST >> +#endif >> + >> +#if defined(CONFIG_TRACE_RECORDER) >> + { >> + .name = "recorder", >> + .args_type = "op:s?,arg:F?", > > Having 'arg' as a filename is a bit odd; using op/arg is very generic > for adding extra commands; but it suddenly becomes less generic if > arg is always a filename. > >> + .params = "trace|dump [arg]", >> + .help = "trace selected recorders or print recorder dump", >> + .cmd = hmp_recorder, >> + }, >> + >> SRST >> ``trace-file on|off|flush`` >> Open, close, or flush the trace file. If no argument is given, the > > I think this SRST chunk is the one that needs updating for recorder. > (The diff has made a bit of a mess, but I think you've copy pasted the > trace-file chunk, but forgotten to update the SRST section). Indeed. I had forgotten to get back to the .hx file and add the documentation. > >> @@ -1120,7 +1136,7 @@ ERST >> >> SRST >> ``dump-guest-memory [-p]`` *filename* *begin* *length* >> - \ >> + \ >> ``dump-guest-memory [-z|-l|-s|-w]`` *filename* >> Dump guest memory to *protocol*. The file can be processed with crash or >> gdb. Without ``-z|-l|-s|-w``, the dump format is ELF. >> @@ -1828,4 +1844,3 @@ ERST >> .sub_table = hmp_info_cmds, >> .flags = "p", >> }, >> - >> diff --git a/monitor/misc.c b/monitor/misc.c >> index 89bb970b00..0094b1860f 100644 >> --- a/monitor/misc.c >> +++ b/monitor/misc.c >> @@ -61,6 +61,9 @@ >> #ifdef CONFIG_TRACE_SIMPLE >> #include "trace/simple.h" >> #endif >> +#ifdef CONFIG_TRACE_RECORDER >> +#include "trace/recorder.h" >> +#endif >> #include "exec/memory.h" >> #include "exec/exec-all.h" >> #include "qemu/option.h" >> @@ -227,6 +230,30 @@ static void hmp_trace_file(Monitor *mon, const QDict *qdict) >> } >> #endif >> >> +#ifdef CONFIG_TRACE_RECORDER >> +static void hmp_recorder(Monitor *mon, const QDict *qdict) >> +{ >> + const char *op = qdict_get_try_str(qdict, "op"); >> + const char *arg = qdict_get_try_str(qdict, "arg"); >> + >> + if (!op) { >> + monitor_printf(mon, "missing recorder command\"%s\"\n", op); >> + help_cmd(mon, "recorder"); >> + } else if (!strcmp(op, "trace")) { >> + recorder_trace_set(arg); >> + } else if (!strcmp(op, "dump")) { >> + if (!arg || !*arg) { >> + recorder_dump(); >> + } else { >> + recorder_dump_for(arg); >> + } >> + } else { >> + monitor_printf(mon, "unexpected recorder command \"%s\"\n", op); >> + help_cmd(mon, "recorder"); >> + } >> +} > > Consider whether just doing two separate commands would be easier; > a recorder-trace and recorder-dump for example; that's fine from a HMP > point of view and I think you'll find it's less code. Hmmm. Looking back at the code, I see that I should also probably name the commands something beginning with trace. Maybe trace-record and trace-dump? > > Dave > >> +#endif >> + >> static void hmp_info_help(Monitor *mon, const QDict *qdict) >> { >> help_cmd(mon, "info"); >> diff --git a/scripts/tracetool/backend/recorder.py b/scripts/tracetool/backend/recorder.py >> new file mode 100644 >> index 0000000000..79cc6f5b03 >> --- /dev/null >> +++ b/scripts/tracetool/backend/recorder.py >> @@ -0,0 +1,51 @@ >> +# -*- coding: utf-8 -*- >> + >> +""" >> +Trace back-end for recorder library >> +""" >> + >> +__author__ = "Christophe de Dinechin " >> +__copyright__ = "Copyright 2020, Christophe de Dinechin and Red Hat" >> +__license__ = "GPL version 2 or (at your option) any later version" >> + >> +__maintainer__ = "Christophe de Dinechin" >> +__email__ = "christophe@dinechin.org" >> + >> + >> +from tracetool import out >> + >> +PUBLIC = True >> + >> +def generate_h_begin(events, group): >> + out('#include ', '') >> + >> + for event in events: >> + out('RECORDER_DECLARE(%(name)s);', name=event.name) >> + >> + >> +def generate_h(event, group): >> + argnames = ", ".join(event.args.names()) >> + if len(event.args) > 0: >> + argnames = ", " + argnames >> + >> + out(' record(%(event)s, %(fmt)s %(argnames)s);', >> + event=event.name, >> + fmt=event.fmt.rstrip("\n"), >> + argnames=argnames) >> + >> + >> +def generate_h_backend_dstate(event, group): >> + out(' RECORDER_TWEAK(%(event_id)s) || \\', event_id=event.name) >> + >> +def generate_c_begin(events, group): >> + out('#include "qemu/osdep.h"', >> + '#include "trace/control.h"', >> + '#include "trace/simple.h"', >> + '#include ', >> + '') >> + >> + for event in events: >> + out('RECORDER_DEFINE(%(name)s, 8, "Tracetool recorder for %(api)s(%(args)s)");', >> + name=event.name, >> + api=event.api(), >> + args=event.args) >> diff --git a/trace/Makefile.objs b/trace/Makefile.objs >> index c544509adf..9e347640c2 100644 >> --- a/trace/Makefile.objs >> +++ b/trace/Makefile.objs >> @@ -54,6 +54,8 @@ $(obj)/generated-tcg-tracers.h-timestamp: $(SRC_PATH)/trace-events $(BUILD_DIR)/ >> >> util-obj-$(CONFIG_TRACE_SIMPLE) += simple.o >> util-obj-$(CONFIG_TRACE_FTRACE) += ftrace.o >> +util-obj-$(CONFIG_TRACE_RECORDER) += recorder.o >> +recorder.o-libs = -lrecorder >> util-obj-y += control.o >> obj-y += control-target.o >> util-obj-y += qmp.o >> diff --git a/trace/control.c b/trace/control.c >> index 2ffe000818..15e5293eec 100644 >> --- a/trace/control.c >> +++ b/trace/control.c >> @@ -23,6 +23,9 @@ >> #ifdef CONFIG_TRACE_SYSLOG >> #include >> #endif >> +#ifdef CONFIG_TRACE_RECORDER >> +#include "trace/recorder.h" >> +#endif >> #include "qapi/error.h" >> #include "qemu/error-report.h" >> #include "qemu/config-file.h" >> @@ -282,6 +285,10 @@ bool trace_init_backends(void) >> openlog(NULL, LOG_PID, LOG_DAEMON); >> #endif >> >> +#ifdef CONFIG_TRACE_RECORDER >> + recorder_trace_init(); >> +#endif >> + >> return true; >> } >> >> diff --git a/trace/recorder.c b/trace/recorder.c >> new file mode 100644 >> index 0000000000..cbc22ee2d5 >> --- /dev/null >> +++ b/trace/recorder.c >> @@ -0,0 +1,22 @@ >> +/* >> + * Recorder-based trace backend >> + * >> + * Copyright Red Hat 2020 >> + * >> + * This work is licensed under the terms of the GNU GPL, version 2. See >> + * the COPYING file in the top-level directory. >> + * >> + */ >> + >> +#include "trace/recorder.h" >> + >> +RECORDER_CONSTRUCTOR >> +void recorder_trace_init(void) >> +{ >> + recorder_trace_set(getenv("RECORDER_TRACES")); >> + >> + // Allow a dump in case we receive some unhandled signal >> + // For example, send USR2 to a hung process to get a dump >> + if (getenv("RECORDER_TRACES")) >> + recorder_dump_on_common_signals(0,0); >> +} >> diff --git a/trace/recorder.h b/trace/recorder.h >> new file mode 100644 >> index 0000000000..00b11a2d2f >> --- /dev/null >> +++ b/trace/recorder.h >> @@ -0,0 +1,34 @@ >> +/* >> + * Recorder-based trace backend >> + * >> + * Copyright Red Hat 2020 >> + * >> + * This work is licensed under the terms of the GNU GPL, version 2. See >> + * the COPYING file in the top-level directory. >> + * >> + */ >> + >> +#ifndef TRACE_RECORDER_H >> +#define TRACE_RECORDER_H >> + >> +#include "qemu/osdep.h" >> + >> +#ifdef CONFIG_TRACE_RECORDER >> + >> +#include >> + >> +extern void recorder_trace_init(void); >> + >> +#else >> + >> +// Disable recorder macros >> +#define RECORDER(Name, Size, Description) >> +#define RECORDER_DEFINE(Name, Size, Description) >> +#define RECORDER_DECLARE(Name) >> +#define RECORD(Name, ...) >> +#define record(Name, ...) >> +#define recorder_trace_init() >> + >> +#endif // CONFIG_TRACE_RECORDER >> + >> +#endif // TRACE_RECORDER_H >> diff --git a/util/module.c b/util/module.c >> index e48d9aacc0..2fa93561fe 100644 >> --- a/util/module.c >> +++ b/util/module.c >> @@ -22,6 +22,10 @@ >> #ifdef CONFIG_MODULE_UPGRADES >> #include "qemu-version.h" >> #endif >> +#ifdef CONFIG_TRACE_RECORDER >> +#include "trace/recorder.h" >> +#endif >> + >> >> typedef struct ModuleEntry >> { >> @@ -150,6 +154,10 @@ static int module_load_file(const char *fname) >> g_module_close(g_module); >> ret = -EINVAL; >> } else { >> +#ifdef CONFIG_TRACE_RECORDER >> + // New recorders may have been pulled in, activate them if necessary >> + recorder_trace_init(); >> +#endif >> QTAILQ_FOREACH(e, &dso_init_list, node) { >> e->init(); >> register_module_init(e->init, e->type); >> -- >> 2.26.2 >> -- Cheers, Christophe de Dinechin (IRC c3d)