As part of the discussions for user_events aligning to be used with eBPF
it became clear [1] we needed a way to delete events without having to rely
upon the delete IOCTL. Steven suggested that we simply have an owner
for the event, however, the event can be held by more than just the
first register FD, such as perf/ftrace or additional registers. In order
to handle all those cases, we must only delete after all references are
gone from both user and kernel space.
This series adds a internal register flag, USER_EVENT_REG_PERSIST, which
causes the event to not delete itself upon the last put reference. We
cannot fully drop the delete IOCTL, since we still want to enable events to
be registered early via dynamic_events and persist. Events that do not use
this new flag are auto-cleaned up upon no longer being used. This new flag
is not exposed to user processes yet while we work out the details, however,
the code is updated to accomodate it once it is ready.
1: https://lore.kernel.org/linux-trace-kernel/[email protected]/
Change history
v3:
Rebased to trace/urgent as requested by Steven
Removed user-facing references to USER_EVENT_REG_PERSIST while we work out
the details
Added check for any flags, even from dynamic_events, will return -EINVAL
Added clarifying comment about event_mutex protection of refcounts
Updated selftests to work given the absence of persist events
Updated documentation to not include /sys/kernel/tracing/dynamic_events since
they cannot be used until persist flags exist and a note about auto-deletions
v2:
Renamed series to "Add auto cleanup and a flag to persist events"
Changed auto-delete to be default behavior, with new flag to persist events
Beau Belgrave (6):
tracing/user_events: Store register flags on events
tracing/user_events: Track refcount consistently via put/get
tracing/user_events: Add auto cleanup and future persist flag
selftests/user_events: Ensure auto cleanup works as expected
selftests/user_events: Adapt dyn_test to non-persist events
tracing/user_events: Document auto-cleanup and remove dyn_event refs
Documentation/trace/user_events.rst | 7 +-
kernel/trace/trace_events_user.c | 208 ++++++++++++++----
.../testing/selftests/user_events/dyn_test.c | 177 +++++++++++----
.../selftests/user_events/ftrace_test.c | 49 ++++-
4 files changed, 346 insertions(+), 95 deletions(-)
base-commit: a8c5c6a5c87ea10189ec43483f44800a4ec97785
--
2.25.1
Now user_events auto-cleanup upon the last reference by default. This
makes it not possible to use the dynamics event file via tracefs.
Document that auto-cleanup is enabled by default and remove the refernce
to /sys/kernel/tracing/dynamic_events file to make this clear.
Signed-off-by: Beau Belgrave <[email protected]>
---
Documentation/trace/user_events.rst | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/Documentation/trace/user_events.rst b/Documentation/trace/user_events.rst
index f79987e16cf4..e7b07313550a 100644
--- a/Documentation/trace/user_events.rst
+++ b/Documentation/trace/user_events.rst
@@ -14,10 +14,6 @@ Programs can view status of the events via
/sys/kernel/tracing/user_events_status and can both register and write
data out via /sys/kernel/tracing/user_events_data.
-Programs can also use /sys/kernel/tracing/dynamic_events to register and
-delete user based events via the u: prefix. The format of the command to
-dynamic_events is the same as the ioctl with the u: prefix applied.
-
Typically programs will register a set of events that they wish to expose to
tools that can read trace_events (such as ftrace and perf). The registration
process tells the kernel which address and bit to reflect if any tool has
@@ -144,6 +140,9 @@ its name. Delete will only succeed if there are no references left to the
event (in both user and kernel space). User programs should use a separate file
to request deletes than the one used for registration due to this.
+**NOTE:** By default events will auto-delete when there are no references left
+to the event. Flags in the future may change this logic.
+
Unregistering
-------------
If after registering an event it is no longer wanted to be updated then it can
--
2.25.1
Currently we don't have any available flags for user processes to use to
indicate options for user_events. We will soon have a flag to indicate
the event should or should not auto-delete once it's not being used by
anyone.
Add a reg_flags field to user_events and parameters to existing
functions to allow for this in future patches.
Signed-off-by: Beau Belgrave <[email protected]>
---
kernel/trace/trace_events_user.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)
diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
index cf6d4c02c363..629823e21447 100644
--- a/kernel/trace/trace_events_user.c
+++ b/kernel/trace/trace_events_user.c
@@ -87,6 +87,7 @@ struct user_event {
struct list_head validators;
refcount_t refcnt;
int min_size;
+ int reg_flags;
char status;
};
@@ -165,7 +166,7 @@ typedef void (*user_event_func_t) (struct user_event *user, struct iov_iter *i,
static int user_event_parse(struct user_event_group *group, char *name,
char *args, char *flags,
- struct user_event **newuser);
+ struct user_event **newuser, int reg_flags);
static struct user_event_mm *user_event_mm_get(struct user_event_mm *mm);
static struct user_event_mm *user_event_mm_get_all(struct user_event *user);
@@ -810,7 +811,8 @@ static struct list_head *user_event_get_fields(struct trace_event_call *call)
* Upon success user_event has its ref count increased by 1.
*/
static int user_event_parse_cmd(struct user_event_group *group,
- char *raw_command, struct user_event **newuser)
+ char *raw_command, struct user_event **newuser,
+ int reg_flags)
{
char *name = raw_command;
char *args = strpbrk(name, " ");
@@ -824,7 +826,7 @@ static int user_event_parse_cmd(struct user_event_group *group,
if (flags)
*flags++ = '\0';
- return user_event_parse(group, name, args, flags, newuser);
+ return user_event_parse(group, name, args, flags, newuser, reg_flags);
}
static int user_field_array_size(const char *type)
@@ -1588,7 +1590,7 @@ static int user_event_create(const char *raw_command)
mutex_lock(&group->reg_mutex);
- ret = user_event_parse_cmd(group, name, &user);
+ ret = user_event_parse_cmd(group, name, &user, 0);
if (!ret)
refcount_dec(&user->refcnt);
@@ -1751,7 +1753,7 @@ static int user_event_trace_register(struct user_event *user)
*/
static int user_event_parse(struct user_event_group *group, char *name,
char *args, char *flags,
- struct user_event **newuser)
+ struct user_event **newuser, int reg_flags)
{
int ret;
u32 key;
@@ -1846,6 +1848,8 @@ static int user_event_parse(struct user_event_group *group, char *name,
if (ret)
goto put_user_lock;
+ user->reg_flags = reg_flags;
+
/* Ensure we track self ref and caller ref (2) */
refcount_set(&user->refcnt, 2);
@@ -2144,7 +2148,7 @@ static long user_events_ioctl_reg(struct user_event_file_info *info,
return ret;
}
- ret = user_event_parse_cmd(info->group, name, &user);
+ ret = user_event_parse_cmd(info->group, name, &user, reg.flags);
if (ret) {
kfree(name);
--
2.25.1
Now that user_events does not honor persist events the dynamic_events
file cannot be easily used to test parsing and matching cases.
Update dyn_test to use the direct ABI file instead of dynamic_events so
that we still have testing coverage until persist events and
dynamic_events file integration has been decided.
Signed-off-by: Beau Belgrave <[email protected]>
---
.../testing/selftests/user_events/dyn_test.c | 177 ++++++++++++++----
1 file changed, 136 insertions(+), 41 deletions(-)
diff --git a/tools/testing/selftests/user_events/dyn_test.c b/tools/testing/selftests/user_events/dyn_test.c
index 8879a7b04c6a..d6979a48478f 100644
--- a/tools/testing/selftests/user_events/dyn_test.c
+++ b/tools/testing/selftests/user_events/dyn_test.c
@@ -16,42 +16,140 @@
#include "../kselftest_harness.h"
-const char *dyn_file = "/sys/kernel/tracing/dynamic_events";
-const char *clear = "!u:__test_event";
+const char *abi_file = "/sys/kernel/tracing/user_events_data";
+const char *enable_file = "/sys/kernel/tracing/events/user_events/__test_event/enable";
-static int Append(const char *value)
+static bool wait_for_delete(void)
{
- int fd = open(dyn_file, O_RDWR | O_APPEND);
- int ret = write(fd, value, strlen(value));
+ int i;
+
+ for (i = 0; i < 1000; ++i) {
+ int fd = open(enable_file, O_RDONLY);
+
+ if (fd == -1)
+ return true;
+
+ close(fd);
+ usleep(1000);
+ }
+
+ return false;
+}
+
+static int reg_event(int fd, int *check, int bit, const char *value)
+{
+ struct user_reg reg = {0};
+
+ reg.size = sizeof(reg);
+ reg.name_args = (__u64)value;
+ reg.enable_bit = bit;
+ reg.enable_addr = (__u64)check;
+ reg.enable_size = sizeof(*check);
+
+ if (ioctl(fd, DIAG_IOCSREG, ®) == -1)
+ return -1;
+
+ return 0;
+}
+
+static int unreg_event(int fd, int *check, int bit)
+{
+ struct user_unreg unreg = {0};
+
+ unreg.size = sizeof(unreg);
+ unreg.disable_bit = bit;
+ unreg.disable_addr = (__u64)check;
+
+ return ioctl(fd, DIAG_IOCSUNREG, &unreg);
+}
+
+static int parse(int *check, const char *value)
+{
+ int fd = open(abi_file, O_RDWR);
+ int ret;
+
+ if (fd == -1)
+ return -1;
+
+ /* Until we have persist flags via dynamic events, use the base name */
+ if (value[0] != 'u' || value[1] != ':') {
+ close(fd);
+ return -1;
+ }
+
+ ret = reg_event(fd, check, 31, value + 2);
+
+ if (ret != -1) {
+ if (unreg_event(fd, check, 31) == -1)
+ printf("WARN: Couldn't unreg event\n");
+ }
close(fd);
+
return ret;
}
-#define CLEAR() \
+static int check_match(int *check, const char *first, const char *second, bool *match)
+{
+ int fd = open(abi_file, O_RDWR);
+ int ret = -1;
+
+ if (fd == -1)
+ return -1;
+
+ if (reg_event(fd, check, 31, first) == -1)
+ goto cleanup;
+
+ if (reg_event(fd, check, 30, second) == -1) {
+ if (errno == EADDRINUSE) {
+ /* Name is in use, with different fields */
+ *match = false;
+ ret = 0;
+ }
+
+ goto cleanup;
+ }
+
+ *match = true;
+ ret = 0;
+cleanup:
+ unreg_event(fd, check, 31);
+ unreg_event(fd, check, 30);
+
+ close(fd);
+
+ wait_for_delete();
+
+ return ret;
+}
+
+#define TEST_MATCH(x, y) \
do { \
- int ret = Append(clear); \
- if (ret == -1) \
- ASSERT_EQ(ENOENT, errno); \
+ bool match; \
+ ASSERT_NE(-1, check_match(&self->check, x, y, &match)); \
+ ASSERT_EQ(true, match); \
} while (0)
-#define TEST_PARSE(x) \
+#define TEST_NMATCH(x, y) \
do { \
- ASSERT_NE(-1, Append(x)); \
- CLEAR(); \
+ bool match; \
+ ASSERT_NE(-1, check_match(&self->check, x, y, &match)); \
+ ASSERT_EQ(false, match); \
} while (0)
-#define TEST_NPARSE(x) ASSERT_EQ(-1, Append(x))
+#define TEST_PARSE(x) ASSERT_NE(-1, parse(&self->check, x))
+
+#define TEST_NPARSE(x) ASSERT_EQ(-1, parse(&self->check, x))
FIXTURE(user) {
+ int check;
};
FIXTURE_SETUP(user) {
- CLEAR();
}
FIXTURE_TEARDOWN(user) {
- CLEAR();
+ wait_for_delete();
}
TEST_F(user, basic_types) {
@@ -95,33 +193,30 @@ TEST_F(user, size_types) {
TEST_NPARSE("u:__test_event char a 20");
}
-TEST_F(user, flags) {
- /* Should work */
- TEST_PARSE("u:__test_event:BPF_ITER u32 a");
- /* Forward compat */
- TEST_PARSE("u:__test_event:BPF_ITER,FLAG_FUTURE u32 a");
-}
-
TEST_F(user, matching) {
- /* Register */
- ASSERT_NE(-1, Append("u:__test_event struct custom a 20"));
- /* Should not match */
- TEST_NPARSE("!u:__test_event struct custom b");
- /* Should match */
- TEST_PARSE("!u:__test_event struct custom a");
- /* Multi field reg */
- ASSERT_NE(-1, Append("u:__test_event u32 a; u32 b"));
- /* Non matching cases */
- TEST_NPARSE("!u:__test_event u32 a");
- TEST_NPARSE("!u:__test_event u32 b");
- TEST_NPARSE("!u:__test_event u32 a; u32 ");
- TEST_NPARSE("!u:__test_event u32 a; u32 a");
- /* Matching case */
- TEST_PARSE("!u:__test_event u32 a; u32 b");
- /* Register */
- ASSERT_NE(-1, Append("u:__test_event u32 a; u32 b"));
- /* Ensure trailing semi-colon case */
- TEST_PARSE("!u:__test_event u32 a; u32 b;");
+ /* Single name matches */
+ TEST_MATCH("__test_event u32 a",
+ "__test_event u32 a");
+
+ /* Multiple names match */
+ TEST_MATCH("__test_event u32 a; u32 b",
+ "__test_event u32 a; u32 b");
+
+ /* Multiple names match with dangling ; */
+ TEST_MATCH("__test_event u32 a; u32 b",
+ "__test_event u32 a; u32 b;");
+
+ /* Single name doesn't match */
+ TEST_NMATCH("__test_event u32 a",
+ "__test_event u32 b");
+
+ /* Multiple names don't match */
+ TEST_NMATCH("__test_event u32 a; u32 b",
+ "__test_event u32 b; u32 a");
+
+ /* Types don't match */
+ TEST_NMATCH("__test_event u64 a; u64 b",
+ "__test_event u32 a; u32 b");
}
int main(int argc, char **argv)
--
2.25.1