On 6/8/21 6:10 PM, Emily Shaffer wrote:
It can be useful to tell who invoked Git - was it invoked manually by a
user via CLI or script? By an IDE? In some cases - like 'repo' tool -
we can influence the source code and set the GIT_TRACE2_PARENT_SID
environment variable from the caller process. In 'repo''s case, that
parent SID is manipulated to include the string "repo", which means we
can positively identify when Git was invoked by 'repo' tool. However,
identifying parents that way requires both that we know which tools
invoke Git and that we have the ability to modify the source code of
those tools. It cannot scale to keep up with the various IDEs and
wrappers which use Git, most of which we don't know about. Learning
which tools and wrappers invoke Git, and how, would give us insight to
decide where to improve Git's usability and performance.
Unfortunately, there's no cross-platform reliable way to gather the name
of the parent process. If procfs is present, we can use that; otherwise
we will need to discover the name another way. However, the process ID
should be sufficient to look up the process name on most platforms, so
that code may be shareable.
Git for Windows gathers similar information and logs it as a "data_json"
event. However, since "data_json" has a variable format, it is difficult
to parse effectively in some languages; instead, let's pursue a
dedicated "cmd_ancestry" event to record information about the ancestry
of the current process and a consistent, parseable way.
Git for Windows also gathers information about more than one generation
of parent. In Linux further ancestry info can be gathered with procfs,
but it's unwieldy to do so. In the interest of later moving Git for
Windows ancestry logging to the 'cmd_ancestry' event, and in the
interest of later adding more ancestry to the Linux implementation - or
of adding this functionality to other platforms which have an easier
time walking the process tree - let's make 'cmd_ancestry' accept an
array of parentage.
Signed-off-by: Emily Shaffer <emilyshaffer@xxxxxxxxxx>
---
Since v4:
Since I'm reading from a file to discover the name of the process, the
file is newline-terminated. This newline caused some havoc in tests, so
it's better to strip it if it's there. It's not part of the process name
itself.
Passing tests at
https://github.com/nasamuffin/git/actions/runs/919722509
Range-diff against v4:
1: efb0a3ccb4 ! 1: 7a7e1ebbfa tr2: log parent process name
@@ compat/procinfo.c (new)
+ strbuf_addf(&procfs_path, "/proc/%d/comm", getppid());
+ if (strbuf_read_file(&name, procfs_path.buf, 0)) {
+ strbuf_release(&procfs_path);
++ strbuf_trim_trailing_newline(&name);
+ strvec_push(names, strbuf_detach(&name, NULL));
+ }
+
You're only getting the name of the command (argv[0]) and not the
full command line, right? That is a good thing.
Documentation/technical/api-trace2.txt | 14 ++++++
Makefile | 5 +++
compat/procinfo.c | 62 ++++++++++++++++++++++++++
config.mak.uname | 1 +
t/t0210/scrub_normal.perl | 6 +++
t/t0211/scrub_perf.perl | 5 +++
t/t0212/parse_events.perl | 5 ++-
trace2.c | 13 ++++++
trace2.h | 12 ++++-
trace2/tr2_tgt.h | 3 ++
trace2/tr2_tgt_event.c | 21 +++++++++
trace2/tr2_tgt_normal.c | 19 ++++++++
trace2/tr2_tgt_perf.c | 16 +++++++
13 files changed, 180 insertions(+), 2 deletions(-)
create mode 100644 compat/procinfo.c
diff --git a/Documentation/technical/api-trace2.txt b/Documentation/technical/api-trace2.txt
index 3f52f981a2..8a0b360a0e 100644
--- a/Documentation/technical/api-trace2.txt
+++ b/Documentation/technical/api-trace2.txt
@@ -493,6 +493,20 @@ about specific error arguments.
}
------------
+`"cmd_ancestry"`::
+ This event contains the text command name for the parent (and earlier
+ generations of parents) of the current process, in an array ordered from
+ nearest parent to furthest great-grandparent. It may not be implemented
+ on all platforms.
++
+------------
+{
+ "event":"cmd_ancestry",
+ ...
+ "ancestry":["bash","tmux: server","systemd"]
Is the second element really "tmux: server". Seems odd that that's what
the command name (argv[0]) is. Perhaps I misread something??
+}
This array is bounded and that implies that you captured all of
the grand parents back to "init" (or whatever it is called these
days).
Is there value in having a final "..." or "(truncated)" element
to indicate that the list incomplete? I did the latter in the
Windows version.
+------------
+
`"cmd_name"`::
This event contains the command name for this git process
and the hierarchy of commands from parent git processes.
diff --git a/Makefile b/Makefile
index 93664d6714..330e4fa011 100644
--- a/Makefile
+++ b/Makefile
@@ -1889,6 +1889,11 @@ ifneq ($(PROCFS_EXECUTABLE_PATH),)
BASIC_CFLAGS += '-DPROCFS_EXECUTABLE_PATH="$(procfs_executable_path_SQ)"'
endif
+ifdef HAVE_PROCFS_LINUX
+ BASIC_CFLAGS += -DHAVE_PROCFS_LINUX
+ COMPAT_OBJS += compat/procinfo.o
+endif
+
ifdef HAVE_NS_GET_EXECUTABLE_PATH
BASIC_CFLAGS += -DHAVE_NS_GET_EXECUTABLE_PATH
endif
diff --git a/compat/procinfo.c b/compat/procinfo.c
new file mode 100644
index 0000000000..f8763cacf8
--- /dev/null
+++ b/compat/procinfo.c
@@ -0,0 +1,62 @@
+#include "cache.h"
+
+#include "strbuf.h"
+#include "strvec.h"
+#include "trace2.h"
+
+static void get_ancestry_names(struct strvec *names)
+{
+#ifdef HAVE_PROCFS_LINUX
+ /*
+ * NEEDSWORK: We could gather the entire pstree into an array to match
+ * functionality with compat/win32/trace2_win32_process_info.c.
+ * To do so, we may want to examine /proc/<pid>/stat. For now, just
+ * gather the immediate parent name which is readily accessible from
+ * /proc/$(getppid())/comm.
+ */
+ struct strbuf procfs_path = STRBUF_INIT;
+ struct strbuf name = STRBUF_INIT;
+
+ /* try to use procfs if it's present. */
+ strbuf_addf(&procfs_path, "/proc/%d/comm", getppid());
+ if (strbuf_read_file(&name, procfs_path.buf, 0)) {
+ strbuf_release(&procfs_path);
+ strbuf_trim_trailing_newline(&name);
+ strvec_push(names, strbuf_detach(&name, NULL));
+ }
+
+ return;
+#endif
+ /* NEEDSWORK: add non-procfs-linux implementations here */
+}
Perhaps this has already been discussed, but would it be better
to have a "compat/linux/trace2_linux_process_info.c"
or "compat/procfs/trace2_procfs_process_info.c" source file and
only compile it in Linux-compatible builds -- rather than #ifdef'ing
the source. This is a highly platform-specific feature.
For example, if I convert the Win32 version to use your new event,
I wouldn't want to move the code.
I just noticed that you have both "BASIC_CFLAGS+=" and a "COMPAT_OBSJ+="
lines. If you made this source file procfs-specific, you wouldn't need
the ifdef and you could avoid the new CFLAG.
+
+void trace2_collect_process_info(enum trace2_process_info_reason reason)
+{
+ if (!trace2_is_enabled())
+ return;
+
+ /* someday we may want to write something extra here, but not today */
+ if (reason == TRACE2_PROCESS_INFO_EXIT)
+ return;
+
+ if (reason == TRACE2_PROCESS_INFO_STARTUP) {
+ /*
+ * NEEDSWORK: we could do the entire ptree in an array instead,
+ * see compat/win32/trace2_win32_process_info.c.
+ */
+ struct strvec names = STRVEC_INIT;
+
+ get_ancestry_names(&names);
+
+ if (names.nr == 0) {
+ strvec_clear(&names);
+ return;
+ }
+
+ trace2_cmd_ancestry(names.v);
+
+ strvec_clear(&names);
I agree with Junio here, it would be simpler to say it like this:
get_ancestry_names(&names);
if (names.nr)
trace2_cmd_ancestry(names.v);
strvec_clear(&names);
+ }
+
+ return;
+}
diff --git a/config.mak.uname b/config.mak.uname
index cb443b4e02..7ad110a1d2 100644
--- a/config.mak.uname
+++ b/config.mak.uname
@@ -58,6 +58,7 @@ ifeq ($(uname_S),Linux)
FREAD_READS_DIRECTORIES = UnfortunatelyYes
BASIC_CFLAGS += -DHAVE_SYSINFO
PROCFS_EXECUTABLE_PATH = /proc/self/exe
+ HAVE_PROCFS_LINUX = YesPlease
endif
ifeq ($(uname_S),GNU/kFreeBSD)
HAVE_ALLOCA_H = YesPlease
diff --git a/t/t0210/scrub_normal.perl b/t/t0210/scrub_normal.perl
index c65d1a815e..7cc4de392a 100644
--- a/t/t0210/scrub_normal.perl
+++ b/t/t0210/scrub_normal.perl
@@ -42,6 +42,12 @@
# so just omit it for testing purposes.
# print "cmd_path _EXE_\n";
}
+ elsif ($line =~ m/^cmd_ancestry/) {
+ # 'cmd_ancestry' is not implemented everywhere, so for portability's
+ # sake, skip it when parsing normal.
+ #
+ # print "$line";
+ }
else {
print "$line";
}
diff --git a/t/t0211/scrub_perf.perl b/t/t0211/scrub_perf.perl
index 351af7844e..d164b750ff 100644
--- a/t/t0211/scrub_perf.perl
+++ b/t/t0211/scrub_perf.perl
@@ -44,6 +44,11 @@
# $tokens[$col_rest] = "_EXE_";
goto SKIP_LINE;
}
+ elsif ($tokens[$col_event] =~ m/cmd_ancestry/) {
+ # 'cmd_ancestry' is platform-specific and not implemented everywhere,
+ # so skip it.
+ goto SKIP_LINE;
+ }
elsif ($tokens[$col_event] =~ m/child_exit/) {
$tokens[$col_rest] =~ s/ pid:\d* / pid:_PID_ /;
}
diff --git a/t/t0212/parse_events.perl b/t/t0212/parse_events.perl
index 6584bb5634..b6408560c0 100644
--- a/t/t0212/parse_events.perl
+++ b/t/t0212/parse_events.perl
@@ -132,7 +132,10 @@
# just omit it for testing purposes.
# $processes->{$sid}->{'path'} = "_EXE_";
}
-
+ elsif ($event eq 'cmd_ancestry') {
+ # 'cmd_ancestry' is platform-specific and not implemented everywhere, so
+ # just skip it for testing purposes.
+ }
elsif ($event eq 'cmd_name') {
$processes->{$sid}->{'name'} = $line->{'name'};
$processes->{$sid}->{'hierarchy'} = $line->{'hierarchy'};
diff --git a/trace2.c b/trace2.c
index 256120c7fd..b9b154ac44 100644
--- a/trace2.c
+++ b/trace2.c
@@ -260,6 +260,19 @@ void trace2_cmd_path_fl(const char *file, int line, const char *pathname)
tgt_j->pfn_command_path_fl(file, line, pathname);
}
+void trace2_cmd_ancestry_fl(const char *file, int line, const char **parent_names)
+{
+ struct tr2_tgt *tgt_j;
+ int j;
+
+ if (!trace2_enabled)
+ return;
+
+ for_each_wanted_builtin (j, tgt_j)
+ if (tgt_j->pfn_command_ancestry_fl)
+ tgt_j->pfn_command_ancestry_fl(file, line, parent_names);
+}
+
void trace2_cmd_name_fl(const char *file, int line, const char *name)
{
struct tr2_tgt *tgt_j;
diff --git a/trace2.h b/trace2.h
index ede18c2e06..23743ac62b 100644
--- a/trace2.h
+++ b/trace2.h
@@ -133,6 +133,16 @@ void trace2_cmd_path_fl(const char *file, int line, const char *pathname);
#define trace2_cmd_path(p) trace2_cmd_path_fl(__FILE__, __LINE__, (p))
+/*
+ * Emit an 'ancestry' event with the process name of the current process's
+ * parent process.
+ * This gives post-processors a way to determine what invoked the command and
+ * learn more about usage patterns.
+ */
+void trace2_cmd_ancestry_fl(const char *file, int line, const char **parent_names);
+
+#define trace2_cmd_ancestry(v) trace2_cmd_ancestry_fl(__FILE__, __LINE__, (v))
+
/*
* Emit a 'cmd_name' event with the canonical name of the command.
* This gives post-processors a simple field to identify the command
@@ -492,7 +502,7 @@ enum trace2_process_info_reason {
TRACE2_PROCESS_INFO_EXIT,
};
-#if defined(GIT_WINDOWS_NATIVE)
+#if ( defined(GIT_WINDOWS_NATIVE) || defined(HAVE_PROCFS_LINUX) )
void trace2_collect_process_info(enum trace2_process_info_reason reason);
#else
#define trace2_collect_process_info(reason) \
diff --git a/trace2/tr2_tgt.h b/trace2/tr2_tgt.h
index 7b90469212..1f66fd6573 100644
--- a/trace2/tr2_tgt.h
+++ b/trace2/tr2_tgt.h
@@ -27,6 +27,8 @@ typedef void(tr2_tgt_evt_error_va_fl_t)(const char *file, int line,
typedef void(tr2_tgt_evt_command_path_fl_t)(const char *file, int line,
const char *command_path);
+typedef void(tr2_tgt_evt_command_ancestry_fl_t)(const char *file, int line,
+ const char **parent_names);
typedef void(tr2_tgt_evt_command_name_fl_t)(const char *file, int line,
const char *name,
const char *hierarchy);
@@ -108,6 +110,7 @@ struct tr2_tgt {
tr2_tgt_evt_atexit_t *pfn_atexit;
tr2_tgt_evt_error_va_fl_t *pfn_error_va_fl;
tr2_tgt_evt_command_path_fl_t *pfn_command_path_fl;
+ tr2_tgt_evt_command_ancestry_fl_t *pfn_command_ancestry_fl;
tr2_tgt_evt_command_name_fl_t *pfn_command_name_fl;
tr2_tgt_evt_command_mode_fl_t *pfn_command_mode_fl;
tr2_tgt_evt_alias_fl_t *pfn_alias_fl;
diff --git a/trace2/tr2_tgt_event.c b/trace2/tr2_tgt_event.c
index 6353e8ad91..578a9a5287 100644
--- a/trace2/tr2_tgt_event.c
+++ b/trace2/tr2_tgt_event.c
@@ -261,6 +261,26 @@ static void fn_command_path_fl(const char *file, int line, const char *pathname)
jw_release(&jw);
}
+static void fn_command_ancestry_fl(const char *file, int line, const char **parent_names)
+{
+ const char *event_name = "cmd_ancestry";
+ const char *parent_name = NULL;
+ struct json_writer jw = JSON_WRITER_INIT;
+
+ jw_object_begin(&jw, 0);
+ event_fmt_prepare(event_name, file, line, NULL, &jw);
+ jw_object_inline_begin_array(&jw, "ancestry");
+
+ while ((parent_name = *parent_names++))
+ jw_array_string(&jw, parent_name);
+
+ jw_end(&jw); /* 'ancestry' array */
+ jw_end(&jw); /* event object */
+
+ tr2_dst_write_line(&tr2dst_event, &jw.json);
+ jw_release(&jw);
+}
+
static void fn_command_name_fl(const char *file, int line, const char *name,
const char *hierarchy)
{
@@ -584,6 +604,7 @@ struct tr2_tgt tr2_tgt_event = {
fn_atexit,
fn_error_va_fl,
fn_command_path_fl,
+ fn_command_ancestry_fl,
fn_command_name_fl,
fn_command_mode_fl,
fn_alias_fl,
diff --git a/trace2/tr2_tgt_normal.c b/trace2/tr2_tgt_normal.c
index 31b602c171..a5751c8864 100644
--- a/trace2/tr2_tgt_normal.c
+++ b/trace2/tr2_tgt_normal.c
@@ -160,6 +160,24 @@ static void fn_command_path_fl(const char *file, int line, const char *pathname)
strbuf_release(&buf_payload);
}
+static void fn_command_ancestry_fl(const char *file, int line, const char **parent_names)
+{
+ const char *parent_name = NULL;
+ struct strbuf buf_payload = STRBUF_INIT;
+
+ /* cmd_ancestry parent <- grandparent <- great-grandparent */
+ strbuf_addstr(&buf_payload, "cmd_ancestry ");
+ while ((parent_name = *parent_names++)) {
+ strbuf_addstr(&buf_payload, parent_name);
+ /* if we'll write another one after this, add a delimiter */
+ if (parent_names && *parent_names)
+ strbuf_addstr(&buf_payload, " <- ");
+ }
+
+ normal_io_write_fl(file, line, &buf_payload);
+ strbuf_release(&buf_payload);
+}
+
static void fn_command_name_fl(const char *file, int line, const char *name,
const char *hierarchy)
{
@@ -306,6 +324,7 @@ struct tr2_tgt tr2_tgt_normal = {
fn_atexit,
fn_error_va_fl,
fn_command_path_fl,
+ fn_command_ancestry_fl,
fn_command_name_fl,
fn_command_mode_fl,
fn_alias_fl,
diff --git a/trace2/tr2_tgt_perf.c b/trace2/tr2_tgt_perf.c
index a8018f18cc..af4d65a0a5 100644
--- a/trace2/tr2_tgt_perf.c
+++ b/trace2/tr2_tgt_perf.c
@@ -253,6 +253,21 @@ static void fn_command_path_fl(const char *file, int line, const char *pathname)
strbuf_release(&buf_payload);
}
+static void fn_command_ancestry_fl(const char *file, int line, const char **parent_names)
+{
+ const char *event_name = "cmd_ancestry";
+ struct strbuf buf_payload = STRBUF_INIT;
+
+ strbuf_addstr(&buf_payload, "ancestry:[");
+ /* It's not an argv but the rules are basically the same. */
+ sq_append_quote_argv_pretty(&buf_payload, parent_names);
+ strbuf_addch(&buf_payload, ']');
+
+ perf_io_write_fl(file, line, event_name, NULL, NULL, NULL, NULL,
+ &buf_payload);
+ strbuf_release(&buf_payload);
+}
+
static void fn_command_name_fl(const char *file, int line, const char *name,
const char *hierarchy)
{
@@ -532,6 +547,7 @@ struct tr2_tgt tr2_tgt_perf = {
fn_atexit,
fn_error_va_fl,
fn_command_path_fl,
+ fn_command_ancestry_fl,
fn_command_name_fl,
fn_command_mode_fl,
fn_alias_fl,
Otherwise, this looks good to me.
Jeff
