[PATCH v3 bpf-next 0/4] cgroup bpf auto-detachment

[PATCH v3 bpf-next 0/4] cgroup bpf auto-detachment

[Roman Gushchin]

This patchset implements a cgroup bpf auto-detachment functionality:
bpf programs are detached as soon as possible after removal of the
cgroup, without waiting for the release of all associated resources.

Patches 2 and 3 are required to implement a corresponding kselftest
in patch 4.

v3:
  1) some minor changes and typo fixes

v2:
  1) removed a bogus check in patch 4
  2) moved buf[len] = 0 in patch 2


Roman Gushchin (4):
  bpf: decouple the lifetime of cgroup_bpf from cgroup itself
  selftests/bpf: convert test_cgrp2_attach2 example into kselftest
  selftests/bpf: enable all available cgroup v2 controllers
  selftests/bpf: add auto-detach test

 include/linux/bpf-cgroup.h                    |   8 +-
 include/linux/cgroup.h                        |  18 +++
 kernel/bpf/cgroup.c                           |  25 ++-
 kernel/cgroup/cgroup.c                        |  11 +-
 samples/bpf/Makefile                          |   2 -
 tools/testing/selftests/bpf/Makefile          |   4 +-
 tools/testing/selftests/bpf/cgroup_helpers.c  |  57 +++++++
 .../selftests/bpf/test_cgroup_attach.c        | 146 ++++++++++++++++--
 8 files changed, 243 insertions(+), 28 deletions(-)
 rename samples/bpf/test_cgrp2_attach2.c => tools/testing/selftests/bpf/test_cgroup_attach.c (79%)

-- 
2.20.1

[PATCH v3 bpf-next 2/4] selftests/bpf: convert test_cgrp2_attach2 example into kselftest

[Roman Gushchin]

Convert test_cgrp2_attach2 example into a proper test_cgroup_attach
kselftest. It's better because we do run kselftest on a constant
basis, so there are better chances to spot a potential regression.

Also make it slightly less verbose to conform kselftests output style.

Output example:
  $ ./test_cgroup_attach
  #override:PASS
  #multi:PASS
  test_cgroup_attach:PASS

Signed-off-by: Roman Gushchin <guro@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
---
 samples/bpf/Makefile                          |  2 -
 tools/testing/selftests/bpf/Makefile          |  4 +-
 .../selftests/bpf/test_cgroup_attach.c        | 50 ++++++++++++-------
 3 files changed, 36 insertions(+), 20 deletions(-)
 rename samples/bpf/test_cgrp2_attach2.c => tools/testing/selftests/bpf/test_cgroup_attach.c (91%)

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 4f0a1cdbfe7c..253e5a2856be 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -26,7 +26,6 @@ hostprogs-y += map_perf_test
 hostprogs-y += test_overhead
 hostprogs-y += test_cgrp2_array_pin
 hostprogs-y += test_cgrp2_attach
-hostprogs-y += test_cgrp2_attach2
 hostprogs-y += test_cgrp2_sock
 hostprogs-y += test_cgrp2_sock2
 hostprogs-y += xdp1
@@ -81,7 +80,6 @@ map_perf_test-objs := bpf_load.o map_perf_test_user.o
 test_overhead-objs := bpf_load.o test_overhead_user.o
 test_cgrp2_array_pin-objs := test_cgrp2_array_pin.o
 test_cgrp2_attach-objs := test_cgrp2_attach.o
-test_cgrp2_attach2-objs := test_cgrp2_attach2.o $(CGROUP_HELPERS)
 test_cgrp2_sock-objs := test_cgrp2_sock.o
 test_cgrp2_sock2-objs := bpf_load.o test_cgrp2_sock2.o
 xdp1-objs := xdp1_user.o
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 66f2dca1dee1..e09f419f4d7e 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -23,7 +23,8 @@ TEST_GEN_PROGS = test_verifier test_tag test_maps test_lru_map test_lpm_map test
 	test_align test_verifier_log test_dev_cgroup test_tcpbpf_user \
 	test_sock test_btf test_sockmap test_lirc_mode2_user get_cgroup_id_user \
 	test_socket_cookie test_cgroup_storage test_select_reuseport test_section_names \
-	test_netcnt test_tcpnotify_user test_sock_fields test_sysctl
+	test_netcnt test_tcpnotify_user test_sock_fields test_sysctl \
+	test_cgroup_attach
 
 BPF_OBJ_FILES = $(patsubst %.c,%.o, $(notdir $(wildcard progs/*.c)))
 TEST_GEN_FILES = $(BPF_OBJ_FILES)
@@ -96,6 +97,7 @@ $(OUTPUT)/test_cgroup_storage: cgroup_helpers.c
 $(OUTPUT)/test_netcnt: cgroup_helpers.c
 $(OUTPUT)/test_sock_fields: cgroup_helpers.c
 $(OUTPUT)/test_sysctl: cgroup_helpers.c
+$(OUTPUT)/test_cgroup_attach: cgroup_helpers.c
 
 .PHONY: force
 
diff --git a/samples/bpf/test_cgrp2_attach2.c b/tools/testing/selftests/bpf/test_cgroup_attach.c
similarity index 91%
rename from samples/bpf/test_cgrp2_attach2.c
rename to tools/testing/selftests/bpf/test_cgroup_attach.c
index 0bb6507256b7..2d6d57f50e10 100644
--- a/samples/bpf/test_cgrp2_attach2.c
+++ b/tools/testing/selftests/bpf/test_cgroup_attach.c
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: GPL-2.0
+
 /* eBPF example program:
  *
  * - Creates arraymap in kernel with 4 bytes keys and 8 byte values
@@ -25,20 +27,27 @@
 #include <sys/resource.h>
 #include <sys/time.h>
 #include <unistd.h>
+#include <linux/filter.h>
 
 #include <linux/bpf.h>
 #include <bpf/bpf.h>
 
-#include "bpf_insn.h"
+#include "bpf_util.h"
 #include "bpf_rlimit.h"
 #include "cgroup_helpers.h"
 
 #define FOO		"/foo"
 #define BAR		"/foo/bar/"
-#define PING_CMD	"ping -c1 -w1 127.0.0.1 > /dev/null"
+#define PING_CMD	"ping -q -c1 -w1 127.0.0.1 > /dev/null"
 
 char bpf_log_buf[BPF_LOG_BUF_SIZE];
 
+#ifdef DEBUG
+#define debug(args...) printf(args)
+#else
+#define debug(args...)
+#endif
+
 static int prog_load(int verdict)
 {
 	int ret;
@@ -89,7 +98,7 @@ static int test_foo_bar(void)
 		goto err;
 	}
 
-	printf("Attached DROP prog. This ping in cgroup /foo should fail...\n");
+	debug("Attached DROP prog. This ping in cgroup /foo should fail...\n");
 	assert(system(PING_CMD) != 0);
 
 	/* Create cgroup /foo/bar, get fd, and join it */
@@ -100,7 +109,7 @@ static int test_foo_bar(void)
 	if (join_cgroup(BAR))
 		goto err;
 
-	printf("Attached DROP prog. This ping in cgroup /foo/bar should fail...\n");
+	debug("Attached DROP prog. This ping in cgroup /foo/bar should fail...\n");
 	assert(system(PING_CMD) != 0);
 
 	if (bpf_prog_attach(allow_prog, bar, BPF_CGROUP_INET_EGRESS,
@@ -109,7 +118,7 @@ static int test_foo_bar(void)
 		goto err;
 	}
 
-	printf("Attached PASS prog. This ping in cgroup /foo/bar should pass...\n");
+	debug("Attached PASS prog. This ping in cgroup /foo/bar should pass...\n");
 	assert(system(PING_CMD) == 0);
 
 	if (bpf_prog_detach(bar, BPF_CGROUP_INET_EGRESS)) {
@@ -117,7 +126,7 @@ static int test_foo_bar(void)
 		goto err;
 	}
 
-	printf("Detached PASS from /foo/bar while DROP is attached to /foo.\n"
+	debug("Detached PASS from /foo/bar while DROP is attached to /foo.\n"
 	       "This ping in cgroup /foo/bar should fail...\n");
 	assert(system(PING_CMD) != 0);
 
@@ -132,7 +141,7 @@ static int test_foo_bar(void)
 		goto err;
 	}
 
-	printf("Attached PASS from /foo/bar and detached DROP from /foo.\n"
+	debug("Attached PASS from /foo/bar and detached DROP from /foo.\n"
 	       "This ping in cgroup /foo/bar should pass...\n");
 	assert(system(PING_CMD) == 0);
 
@@ -199,9 +208,9 @@ static int test_foo_bar(void)
 	close(bar);
 	cleanup_cgroup_environment();
 	if (!rc)
-		printf("### override:PASS\n");
+		printf("#override:PASS\n");
 	else
-		printf("### override:FAIL\n");
+		printf("#override:FAIL\n");
 	return rc;
 }
 
@@ -441,19 +450,26 @@ static int test_multiprog(void)
 	close(cg5);
 	cleanup_cgroup_environment();
 	if (!rc)
-		printf("### multi:PASS\n");
+		printf("#multi:PASS\n");
 	else
-		printf("### multi:FAIL\n");
+		printf("#multi:FAIL\n");
 	return rc;
 }
 
-int main(int argc, char **argv)
+int main(void)
 {
-	int rc = 0;
+	int (*tests[])(void) = {test_foo_bar, test_multiprog};
+	int errors = 0;
+	int i;
 
-	rc = test_foo_bar();
-	if (rc)
-		return rc;
+	for (i = 0; i < ARRAY_SIZE(tests); i++)
+		if (tests[i]())
+			errors++;
+
+	if (errors)
+		printf("test_cgroup_attach:FAIL\n");
+	else
+		printf("test_cgroup_attach:PASS\n");
 
-	return test_multiprog();
+	return errors ? EXIT_FAILURE : EXIT_SUCCESS;
 }
-- 
2.20.1

[PATCH v3 bpf-next 3/4] selftests/bpf: enable all available cgroup v2 controllers

[Roman Gushchin]

Enable all available cgroup v2 controllers when setting up
the environment for the bpf kselftests. It's required to properly test
the bpf prog auto-detach feature. Also it will generally increase
the code coverage.

Signed-off-by: Roman Gushchin <guro@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
---
 tools/testing/selftests/bpf/cgroup_helpers.c | 57 ++++++++++++++++++++
 1 file changed, 57 insertions(+)

diff --git a/tools/testing/selftests/bpf/cgroup_helpers.c b/tools/testing/selftests/bpf/cgroup_helpers.c
index 6692a40a6979..0d89f0396be4 100644
--- a/tools/testing/selftests/bpf/cgroup_helpers.c
+++ b/tools/testing/selftests/bpf/cgroup_helpers.c
@@ -33,6 +33,60 @@
 	snprintf(buf, sizeof(buf), "%s%s%s", CGROUP_MOUNT_PATH, \
 		 CGROUP_WORK_DIR, path)
 
+/**
+ * enable_all_controllers() - Enable all available cgroup v2 controllers
+ *
+ * Enable all available cgroup v2 controllers in order to increase
+ * the code coverage.
+ *
+ * If successful, 0 is returned.
+ */
+int enable_all_controllers(char *cgroup_path)
+{
+	char path[PATH_MAX + 1];
+	char buf[PATH_MAX];
+	char *c, *c2;
+	int fd, cfd;
+	size_t len;
+
+	snprintf(path, sizeof(path), "%s/cgroup.controllers", cgroup_path);
+	fd = open(path, O_RDONLY);
+	if (fd < 0) {
+		log_err("Opening cgroup.controllers: %s", path);
+		return 1;
+	}
+
+	len = read(fd, buf, sizeof(buf) - 1);
+	if (len < 0) {
+		close(fd);
+		log_err("Reading cgroup.controllers: %s", path);
+		return 1;
+	}
+	buf[len] = 0;
+	close(fd);
+
+	/* No controllers available? We're probably on cgroup v1. */
+	if (len == 0)
+		return 0;
+
+	snprintf(path, sizeof(path), "%s/cgroup.subtree_control", cgroup_path);
+	cfd = open(path, O_RDWR);
+	if (cfd < 0) {
+		log_err("Opening cgroup.subtree_control: %s", path);
+		return 1;
+	}
+
+	for (c = strtok_r(buf, " ", &c2); c; c = strtok_r(NULL, " ", &c2)) {
+		if (dprintf(cfd, "+%s\n", c) <= 0) {
+			log_err("Enabling controller %s: %s", c, path);
+			close(cfd);
+			return 1;
+		}
+	}
+	close(cfd);
+	return 0;
+}
+
 /**
  * setup_cgroup_environment() - Setup the cgroup environment
  *
@@ -71,6 +125,9 @@ int setup_cgroup_environment(void)
 		return 1;
 	}
 
+	if (enable_all_controllers(cgroup_workdir))
+		return 1;
+
 	return 0;
 }
 
-- 
2.20.1

[PATCH v3 bpf-next 4/4] selftests/bpf: add auto-detach test

[Roman Gushchin]

Add a kselftest to cover bpf auto-detachment functionality.
The test creates a cgroup, associates some resources with it,
attaches a couple of bpf programs and deletes the cgroup.

Then it checks that bpf programs are going away in 5 seconds.

Expected output:
  $ ./test_cgroup_attach
  #override:PASS
  #multi:PASS
  #autodetach:PASS
  test_cgroup_attach:PASS

On a kernel without auto-detaching:
  $ ./test_cgroup_attach
  #override:PASS
  #multi:PASS
  #autodetach:FAIL
  test_cgroup_attach:FAIL

Signed-off-by: Roman Gushchin <guro@fb.com>
---
 .../selftests/bpf/test_cgroup_attach.c        | 98 ++++++++++++++++++-
 1 file changed, 97 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/test_cgroup_attach.c b/tools/testing/selftests/bpf/test_cgroup_attach.c
index 2d6d57f50e10..7671909ee1cb 100644
--- a/tools/testing/selftests/bpf/test_cgroup_attach.c
+++ b/tools/testing/selftests/bpf/test_cgroup_attach.c
@@ -456,9 +456,105 @@ static int test_multiprog(void)
 	return rc;
 }
 
+static int test_autodetach(void)
+{
+	__u32 prog_cnt = 4, attach_flags;
+	int allow_prog[2] = {0};
+	__u32 prog_ids[2] = {0};
+	int cg = 0, i, rc = -1;
+	void *ptr = NULL;
+	int attempts;
+
+	for (i = 0; i < ARRAY_SIZE(allow_prog); i++) {
+		allow_prog[i] = prog_load_cnt(1, 1 << i);
+		if (!allow_prog[i])
+			goto err;
+	}
+
+	if (setup_cgroup_environment())
+		goto err;
+
+	/* create a cgroup, attach two programs and remember their ids */
+	cg = create_and_get_cgroup("/cg_autodetach");
+	if (cg < 0)
+		goto err;
+
+	if (join_cgroup("/cg_autodetach"))
+		goto err;
+
+	for (i = 0; i < ARRAY_SIZE(allow_prog); i++) {
+		if (bpf_prog_attach(allow_prog[i], cg, BPF_CGROUP_INET_EGRESS,
+				    BPF_F_ALLOW_MULTI)) {
+			log_err("Attaching prog[%d] to cg:egress", i);
+			goto err;
+		}
+	}
+
+	/* make sure that programs are attached and run some traffic */
+	assert(bpf_prog_query(cg, BPF_CGROUP_INET_EGRESS, 0, &attach_flags,
+			      prog_ids, &prog_cnt) == 0);
+	assert(system(PING_CMD) == 0);
+
+	/* allocate some memory (4Mb) to pin the original cgroup */
+	ptr = malloc(4 * (1 << 20));
+	if (!ptr)
+		goto err;
+
+	/* close programs and cgroup fd */
+	for (i = 0; i < ARRAY_SIZE(allow_prog); i++) {
+		close(allow_prog[i]);
+		allow_prog[i] = 0;
+	}
+
+	close(cg);
+	cg = 0;
+
+	/* leave the cgroup and remove it. don't detach programs */
+	cleanup_cgroup_environment();
+
+	/* wait for the asynchronous auto-detachment.
+	 * wait for no more than 5 sec and give up.
+	 */
+	for (i = 0; i < ARRAY_SIZE(prog_ids); i++) {
+		for (attempts = 5; attempts >= 0; attempts--) {
+			int fd = bpf_prog_get_fd_by_id(prog_ids[i]);
+
+			if (fd < 0)
+				break;
+
+			/* don't leave the fd open */
+			close(fd);
+
+			if (!attempts)
+				goto err;
+
+			sleep(1);
+		}
+	}
+
+	rc = 0;
+err:
+	for (i = 0; i < ARRAY_SIZE(allow_prog); i++)
+		if (allow_prog[i] > 0)
+			close(allow_prog[i]);
+	if (cg)
+		close(cg);
+	free(ptr);
+	cleanup_cgroup_environment();
+	if (!rc)
+		printf("#autodetach:PASS\n");
+	else
+		printf("#autodetach:FAIL\n");
+	return rc;
+}
+
 int main(void)
 {
-	int (*tests[])(void) = {test_foo_bar, test_multiprog};
+	int (*tests[])(void) = {
+		test_foo_bar,
+		test_multiprog,
+		test_autodetach,
+	};
 	int errors = 0;
 	int i;
 
-- 
2.20.1

Re: [PATCH v3 bpf-next 4/4] selftests/bpf: add auto-detach test

[Yonghong Song]

On 5/23/19 12:45 PM, Roman Gushchin wrote:
> Add a kselftest to cover bpf auto-detachment functionality.
> The test creates a cgroup, associates some resources with it,
> attaches a couple of bpf programs and deletes the cgroup.
> 
> Then it checks that bpf programs are going away in 5 seconds.
> 
> Expected output:
>    $ ./test_cgroup_attach
>    #override:PASS
>    #multi:PASS
>    #autodetach:PASS
>    test_cgroup_attach:PASS
> 
> On a kernel without auto-detaching:
>    $ ./test_cgroup_attach
>    #override:PASS
>    #multi:PASS
>    #autodetach:FAIL
>    test_cgroup_attach:FAIL
> 
> Signed-off-by: Roman Gushchin <guro@fb.com>

Looks good to me. It will be good if you can add test_cgroup_attach
to .gitignore to avoid it shows up in `git status`. With that,

Acked-by: Yonghong Song <yhs@fb.com>

> ---
>   .../selftests/bpf/test_cgroup_attach.c        | 98 ++++++++++++++++++-
>   1 file changed, 97 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/bpf/test_cgroup_attach.c b/tools/testing/selftests/bpf/test_cgroup_attach.c
> index 2d6d57f50e10..7671909ee1cb 100644
> --- a/tools/testing/selftests/bpf/test_cgroup_attach.c
> +++ b/tools/testing/selftests/bpf/test_cgroup_attach.c
> @@ -456,9 +456,105 @@ static int test_multiprog(void)
>   	return rc;
>   }
>   
> +static int test_autodetach(void)
> +{
> +	__u32 prog_cnt = 4, attach_flags;
> +	int allow_prog[2] = {0};
> +	__u32 prog_ids[2] = {0};
> +	int cg = 0, i, rc = -1;
> +	void *ptr = NULL;
> +	int attempts;
> +
> +	for (i = 0; i < ARRAY_SIZE(allow_prog); i++) {
> +		allow_prog[i] = prog_load_cnt(1, 1 << i);
> +		if (!allow_prog[i])
> +			goto err;
> +	}
> +
> +	if (setup_cgroup_environment())
> +		goto err;
> +
> +	/* create a cgroup, attach two programs and remember their ids */
> +	cg = create_and_get_cgroup("/cg_autodetach");
> +	if (cg < 0)
> +		goto err;
> +
> +	if (join_cgroup("/cg_autodetach"))
> +		goto err;
> +
> +	for (i = 0; i < ARRAY_SIZE(allow_prog); i++) {
> +		if (bpf_prog_attach(allow_prog[i], cg, BPF_CGROUP_INET_EGRESS,
> +				    BPF_F_ALLOW_MULTI)) {
> +			log_err("Attaching prog[%d] to cg:egress", i);
> +			goto err;
> +		}
> +	}
> +
> +	/* make sure that programs are attached and run some traffic */
> +	assert(bpf_prog_query(cg, BPF_CGROUP_INET_EGRESS, 0, &attach_flags,
> +			      prog_ids, &prog_cnt) == 0);
> +	assert(system(PING_CMD) == 0);
> +
> +	/* allocate some memory (4Mb) to pin the original cgroup */
> +	ptr = malloc(4 * (1 << 20));
> +	if (!ptr)
> +		goto err;
> +
> +	/* close programs and cgroup fd */
> +	for (i = 0; i < ARRAY_SIZE(allow_prog); i++) {
> +		close(allow_prog[i]);
> +		allow_prog[i] = 0;
> +	}
> +
> +	close(cg);
> +	cg = 0;
> +
> +	/* leave the cgroup and remove it. don't detach programs */
> +	cleanup_cgroup_environment();
> +
> +	/* wait for the asynchronous auto-detachment.
> +	 * wait for no more than 5 sec and give up.
> +	 */
> +	for (i = 0; i < ARRAY_SIZE(prog_ids); i++) {
> +		for (attempts = 5; attempts >= 0; attempts--) {
> +			int fd = bpf_prog_get_fd_by_id(prog_ids[i]);
> +
> +			if (fd < 0)
> +				break;
> +
> +			/* don't leave the fd open */
> +			close(fd);
> +
> +			if (!attempts)
> +				goto err;
> +
> +			sleep(1);
> +		}
> +	}
> +
> +	rc = 0;
> +err:
> +	for (i = 0; i < ARRAY_SIZE(allow_prog); i++)
> +		if (allow_prog[i] > 0)
> +			close(allow_prog[i]);
> +	if (cg)
> +		close(cg);
> +	free(ptr);
> +	cleanup_cgroup_environment();
> +	if (!rc)
> +		printf("#autodetach:PASS\n");
> +	else
> +		printf("#autodetach:FAIL\n");
> +	return rc;
> +}
> +
>   int main(void)
>   {
> -	int (*tests[])(void) = {test_foo_bar, test_multiprog};
> +	int (*tests[])(void) = {
> +		test_foo_bar,
> +		test_multiprog,
> +		test_autodetach,
> +	};
>   	int errors = 0;
>   	int i;
>   
> 

Re: [PATCH v3 bpf-next 4/4] selftests/bpf: add auto-detach test

[Roman Gushchin]

On Thu, May 23, 2019 at 04:09:30PM -0700, Yonghong Song wrote:
> 
> 
> On 5/23/19 12:45 PM, Roman Gushchin wrote:
> > Add a kselftest to cover bpf auto-detachment functionality.
> > The test creates a cgroup, associates some resources with it,
> > attaches a couple of bpf programs and deletes the cgroup.
> > 
> > Then it checks that bpf programs are going away in 5 seconds.
> > 
> > Expected output:
> >    $ ./test_cgroup_attach
> >    #override:PASS
> >    #multi:PASS
> >    #autodetach:PASS
> >    test_cgroup_attach:PASS
> > 
> > On a kernel without auto-detaching:
> >    $ ./test_cgroup_attach
> >    #override:PASS
> >    #multi:PASS
> >    #autodetach:FAIL
> >    test_cgroup_attach:FAIL
> > 
> > Signed-off-by: Roman Gushchin <guro@fb.com>
> 
> Looks good to me. It will be good if you can add test_cgroup_attach
> to .gitignore to avoid it shows up in `git status`. With that,

I don't think it deserves a new version, I'll prepare a separate patch
for it.

> 
> Acked-by: Yonghong Song <yhs@fb.com>

Thank you for the review!

Re: [PATCH v3 bpf-next 4/4] selftests/bpf: add auto-detach test

[Roman Gushchin]

On Thu, May 23, 2019 at 04:09:30PM -0700, Yonghong Song wrote:
> 
> 
> On 5/23/19 12:45 PM, Roman Gushchin wrote:
> > Add a kselftest to cover bpf auto-detachment functionality.
> > The test creates a cgroup, associates some resources with it,
> > attaches a couple of bpf programs and deletes the cgroup.
> > 
> > Then it checks that bpf programs are going away in 5 seconds.
> > 
> > Expected output:
> >    $ ./test_cgroup_attach
> >    #override:PASS
> >    #multi:PASS
> >    #autodetach:PASS
> >    test_cgroup_attach:PASS
> > 
> > On a kernel without auto-detaching:
> >    $ ./test_cgroup_attach
> >    #override:PASS
> >    #multi:PASS
> >    #autodetach:FAIL
> >    test_cgroup_attach:FAIL
> > 
> > Signed-off-by: Roman Gushchin <guro@fb.com>
> 
> Looks good to me. It will be good if you can add test_cgroup_attach
> to .gitignore to avoid it shows up in `git status`. With that,
>

Here it is!

Thanks!

---

From 150fb4db7ab37f0e8b6482386e8830f3d11b64e1 Mon Sep 17 00:00:00 2001
From: Roman Gushchin <guro@fb.com>
Date: Thu, 23 May 2019 16:46:58 -0700
Subject: [PATCH bpf-next] selftests/bpf: add test_cgroup_attach to .gitignore

Add test_cgroup_attach binary to .gitignore.

Signed-off-by: Roman Gushchin <guro@fb.com>
---
 tools/testing/selftests/bpf/.gitignore | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/testing/selftests/bpf/.gitignore b/tools/testing/selftests/bpf/.gitignore
index dd5d69529382..86a546e5e4db 100644
--- a/tools/testing/selftests/bpf/.gitignore
+++ b/tools/testing/selftests/bpf/.gitignore
@@ -22,6 +22,7 @@ test_lirc_mode2_user
 get_cgroup_id_user
 test_skb_cgroup_id_user
 test_socket_cookie
+test_cgroup_attach
 test_cgroup_storage
 test_select_reuseport
 test_flow_dissector
-- 
2.20.1

Re: [PATCH v3 bpf-next 0/4] cgroup bpf auto-detachment

[Alexei Starovoitov]

On Thu, May 23, 2019 at 12:45:28PM -0700, Roman Gushchin wrote:
> This patchset implements a cgroup bpf auto-detachment functionality:
> bpf programs are detached as soon as possible after removal of the
> cgroup, without waiting for the release of all associated resources.

The idea looks great, but doesn't quite work:

$ ./test_cgroup_attach
#override:PASS
[   66.475219] BUG: sleeping function called from invalid context at ../include/linux/percpu-rwsem.h:34
[   66.476095] in_atomic(): 1, irqs_disabled(): 0, pid: 21, name: ksoftirqd/2
[   66.476706] CPU: 2 PID: 21 Comm: ksoftirqd/2 Not tainted 5.2.0-rc1-00211-g1861420d0162 #1564
[   66.477595] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2.el7 04/01/2014
[   66.478360] Call Trace:
[   66.478591]  dump_stack+0x5b/0x8b
[   66.478892]  ___might_sleep+0x22f/0x290
[   66.479230]  cpus_read_lock+0x18/0x50
[   66.479550]  static_key_slow_dec+0x41/0x70
[   66.479914]  cgroup_bpf_release+0x1a6/0x400
[   66.480285]  percpu_ref_switch_to_atomic_rcu+0x203/0x330
[   66.480754]  rcu_core+0x475/0xcc0
[   66.481047]  ? switch_mm_irqs_off+0x684/0xa40
[   66.481422]  ? rcu_note_context_switch+0x260/0x260
[   66.481842]  __do_softirq+0x1cf/0x5ff
[   66.482174]  ? takeover_tasklets+0x5f0/0x5f0
[   66.482542]  ? smpboot_thread_fn+0xab/0x780
[   66.482911]  run_ksoftirqd+0x1a/0x40
[   66.483225]  smpboot_thread_fn+0x3ad/0x780
[   66.483583]  ? sort_range+0x20/0x20
[   66.483894]  ? __kthread_parkme+0xb0/0x190
[   66.484253]  ? sort_range+0x20/0x20
[   66.484562]  ? sort_range+0x20/0x20
[   66.484878]  kthread+0x2e2/0x3e0
[   66.485166]  ? kthread_create_worker_on_cpu+0xb0/0xb0
[   66.485620]  ret_from_fork+0x1f/0x30

Same test runs fine before the patches.

Re: [PATCH v3 bpf-next 0/4] cgroup bpf auto-detachment

[Roman Gushchin]

On Fri, May 24, 2019 at 02:03:23PM -0700, Alexei Starovoitov wrote:
> On Thu, May 23, 2019 at 12:45:28PM -0700, Roman Gushchin wrote:
> > This patchset implements a cgroup bpf auto-detachment functionality:
> > bpf programs are detached as soon as possible after removal of the
> > cgroup, without waiting for the release of all associated resources.
> 
> The idea looks great, but doesn't quite work:
> 
> $ ./test_cgroup_attach
> #override:PASS
> [   66.475219] BUG: sleeping function called from invalid context at ../include/linux/percpu-rwsem.h:34
> [   66.476095] in_atomic(): 1, irqs_disabled(): 0, pid: 21, name: ksoftirqd/2
> [   66.476706] CPU: 2 PID: 21 Comm: ksoftirqd/2 Not tainted 5.2.0-rc1-00211-g1861420d0162 #1564
> [   66.477595] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2.el7 04/01/2014
> [   66.478360] Call Trace:
> [   66.478591]  dump_stack+0x5b/0x8b
> [   66.478892]  ___might_sleep+0x22f/0x290
> [   66.479230]  cpus_read_lock+0x18/0x50
> [   66.479550]  static_key_slow_dec+0x41/0x70
> [   66.479914]  cgroup_bpf_release+0x1a6/0x400
> [   66.480285]  percpu_ref_switch_to_atomic_rcu+0x203/0x330
> [   66.480754]  rcu_core+0x475/0xcc0
> [   66.481047]  ? switch_mm_irqs_off+0x684/0xa40
> [   66.481422]  ? rcu_note_context_switch+0x260/0x260
> [   66.481842]  __do_softirq+0x1cf/0x5ff
> [   66.482174]  ? takeover_tasklets+0x5f0/0x5f0
> [   66.482542]  ? smpboot_thread_fn+0xab/0x780
> [   66.482911]  run_ksoftirqd+0x1a/0x40
> [   66.483225]  smpboot_thread_fn+0x3ad/0x780
> [   66.483583]  ? sort_range+0x20/0x20
> [   66.483894]  ? __kthread_parkme+0xb0/0x190
> [   66.484253]  ? sort_range+0x20/0x20
> [   66.484562]  ? sort_range+0x20/0x20
> [   66.484878]  kthread+0x2e2/0x3e0
> [   66.485166]  ? kthread_create_worker_on_cpu+0xb0/0xb0
> [   66.485620]  ret_from_fork+0x1f/0x30
> 
> Same test runs fine before the patches.
> 

Ouch, static_branch_dec() might block, so it's not possible to call it from
percpu ref counter release callback. It's not what I expected, tbh.

Good catch, thanks!