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6680c162b4
test_cgcore_populated (test_core) and test_cgkill_{simple,tree,forkbomb}
(test_kill) check cgroup.events "populated 0" immediately after reaping
child tasks with waitpid(). This used to work because cgroup_task_exit() in
do_exit() unlinked tasks from css_sets before exit_notify() woke up
waitpid().
d245698d72 ("cgroup: Defer task cgroup unlink until after the task is done
switching out") moved the unlink to cgroup_task_dead() in
finish_task_switch(), which runs after exit_notify(). The populated counter
is now decremented after the parent's waitpid() can return, so there is no
longer a synchronous ordering guarantee. On PREEMPT_RT, where
cgroup_task_dead() is further deferred through lazy irq_work, the race
window is even larger.
The synchronous populated transition was never part of the cgroup interface
contract - it was an implementation artifact. Use cg_read_strcmp_wait() which
retries for up to 1 second, matching what these tests actually need to
verify: that the cgroup eventually becomes unpopulated after all tasks exit.
Fixes: d245698d72 ("cgroup: Defer task cgroup unlink until after the task is done switching out")
Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Tejun Heo <tj@kernel.org>
Tested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Christian Brauner <brauner@kernel.org>
Cc: cgroups@vger.kernel.org
101 lines
3.9 KiB
C
101 lines
3.9 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#include <stdbool.h>
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#include <stdlib.h>
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#ifndef PAGE_SIZE
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#define PAGE_SIZE 4096
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#endif
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#define MB(x) (x << 20)
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#define USEC_PER_SEC 1000000L
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#define NSEC_PER_SEC 1000000000L
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#define TEST_UID 65534 /* usually nobody, any !root is fine */
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#define CG_THREADS_FILE (!cg_test_v1_named ? "cgroup.threads" : "tasks")
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#define CG_NAMED_NAME "selftest"
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#define CG_PATH_FORMAT (!cg_test_v1_named ? "0::%s" : (":name=" CG_NAMED_NAME ":%s"))
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#define DEFAULT_WAIT_INTERVAL_US (100 * 1000) /* 100 ms */
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/*
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* Checks if two given values differ by less than err% of their sum.
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*/
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static inline int values_close(long a, long b, int err)
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{
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return labs(a - b) <= (a + b) / 100 * err;
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}
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/*
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* Checks if two given values differ by less than err% of their sum and assert
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* with detailed debug info if not.
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*/
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static inline int values_close_report(long a, long b, int err)
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{
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long diff = labs(a - b);
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long limit = (a + b) / 100 * err;
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double actual_err = (a + b) ? (100.0 * diff / (a + b)) : 0.0;
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int close = diff <= limit;
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if (!close)
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fprintf(stderr,
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"[FAIL] actual=%ld expected=%ld | diff=%ld | limit=%ld | "
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"tolerance=%d%% | actual_error=%.2f%%\n",
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a, b, diff, limit, err, actual_err);
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return close;
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}
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extern ssize_t read_text(const char *path, char *buf, size_t max_len);
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extern ssize_t write_text(const char *path, char *buf, ssize_t len);
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extern int cg_find_controller_root(char *root, size_t len, const char *controller);
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extern int cg_find_unified_root(char *root, size_t len, bool *nsdelegate);
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extern char *cg_name(const char *root, const char *name);
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extern char *cg_name_indexed(const char *root, const char *name, int index);
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extern char *cg_control(const char *cgroup, const char *control);
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extern int cg_create(const char *cgroup);
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extern int cg_destroy(const char *cgroup);
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extern int cg_read(const char *cgroup, const char *control,
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char *buf, size_t len);
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extern int cg_read_strcmp(const char *cgroup, const char *control,
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const char *expected);
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extern int cg_read_strcmp_wait(const char *cgroup, const char *control,
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const char *expected);
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extern int cg_read_strstr(const char *cgroup, const char *control,
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const char *needle);
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extern long cg_read_long(const char *cgroup, const char *control);
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extern long cg_read_long_fd(int fd);
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long cg_read_key_long(const char *cgroup, const char *control, const char *key);
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long cg_read_key_long_poll(const char *cgroup, const char *control,
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const char *key, long expected, int retries,
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useconds_t wait_interval_us);
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extern long cg_read_lc(const char *cgroup, const char *control);
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extern int cg_write(const char *cgroup, const char *control, char *buf);
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extern int cg_open(const char *cgroup, const char *control, int flags);
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int cg_write_numeric(const char *cgroup, const char *control, long value);
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extern int cg_run(const char *cgroup,
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int (*fn)(const char *cgroup, void *arg),
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void *arg);
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extern int cg_enter(const char *cgroup, int pid);
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extern int cg_enter_current(const char *cgroup);
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extern int cg_enter_current_thread(const char *cgroup);
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extern int cg_run_nowait(const char *cgroup,
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int (*fn)(const char *cgroup, void *arg),
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void *arg);
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extern int cg_wait_for_proc_count(const char *cgroup, int count);
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extern int cg_killall(const char *cgroup);
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int proc_mount_contains(const char *option);
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int cgroup_feature(const char *feature);
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extern ssize_t proc_read_text(int pid, bool thread, const char *item, char *buf, size_t size);
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extern int proc_read_strstr(int pid, bool thread, const char *item, const char *needle);
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extern pid_t clone_into_cgroup(int cgroup_fd);
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extern int clone_reap(pid_t pid, int options);
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extern int clone_into_cgroup_run_wait(const char *cgroup);
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extern int dirfd_open_opath(const char *dir);
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extern int cg_prepare_for_wait(const char *cgroup);
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extern int memcg_prepare_for_wait(const char *cgroup);
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extern int cg_wait_for(int fd);
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extern bool cg_test_v1_named;
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