From mboxrd@z Thu Jan 1 00:00:00 1970 From: Krzysztof Kozlowski Date: Wed, 23 Jun 2021 15:59:10 +0200 Subject: [LTP] [PATCH v3 2/4] syscalls/msgstress04: fix fork failure on small memory systems In-Reply-To: <20210623135912.81156-1-krzysztof.kozlowski@canonical.com> References: <20210623135912.81156-1-krzysztof.kozlowski@canonical.com> Message-ID: <20210623135912.81156-3-krzysztof.kozlowski@canonical.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ltp@lists.linux.it Running syscalls/msgstress04 on a system with less than ~4 GB of RAM fails: Fork failure in the first child of child group 4396 Fork failure in the second child of child group 4413 msgstress04 1 TFAIL : msgstress04.c:222: Child exit status = 1 The reason is cgroups pid limit set by systemd user.slice. The limit is set for login session, also for root user. For example on 2 GB RAM machine it is set as: /sys/fs/cgroup/pids/user.slice/user-0.slice/pids.max:5207 Read the maximum number of pids and adjust the test limit. Signed-off-by: Krzysztof Kozlowski --- include/tst_pid.h | 4 ++- lib/tst_pid.c | 79 ++++++++++++++++++++++++++++++++++++++++++++++- 2 files changed, 81 insertions(+), 2 deletions(-) diff --git a/include/tst_pid.h b/include/tst_pid.h index 6c42f73a57e7..8d999a655f1a 100644 --- a/include/tst_pid.h +++ b/include/tst_pid.h @@ -14,7 +14,9 @@ pid_t tst_get_unused_pid_(void (*cleanup_fn)(void)); /* * Returns number of free pids by subtraction of the number of pids - * currently used ('ps -eT') from max_pids + * currently used ('ps -eT') from maximum number of processes. + * The limit of processes come from kernel pid_max and cgroup session limits + * (e.g. configured by systemd user.slice). */ int tst_get_free_pids_(void (*cleanup_fn)(void)); diff --git a/lib/tst_pid.c b/lib/tst_pid.c index 9568cc9e91d2..c1ea3fe90e83 100644 --- a/lib/tst_pid.c +++ b/lib/tst_pid.c @@ -18,14 +18,20 @@ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ +#include #include #include +#include +#include #include +#include #include "test.h" #include "tst_pid.h" #include "old_safe_file_ops.h" #define PID_MAX_PATH "/proc/sys/kernel/pid_max" +#define CGROUPS_V1_SLICE_FMT "/sys/fs/cgroup/pids/user.slice/user-%d.slice/pids.max" +#define CGROUPS_V2_SLICE_FMT "/sys/fs/cgroup/user.slice/user-%d.slice/pids.max" pid_t tst_get_unused_pid_(void (*cleanup_fn) (void)) { @@ -36,10 +42,77 @@ pid_t tst_get_unused_pid_(void (*cleanup_fn) (void)) return pid; } +/* + * Get the effective session UID - either one invoking current test via sudo + * or the real UID. + */ +static int get_session_uid(void) +{ + const char *sudo_uid; + + sudo_uid = getenv("SUDO_UID"); + if (sudo_uid) { + int real_uid; + + TEST(sscanf(sudo_uid, "%u", &real_uid)); + if (TEST_RETURN != 1) { +#ifdef DEBUG + tst_resm(TINFO, "No SUDO_UID from env"); +#endif + } else { + return real_uid; + } + } + + return getuid(); +} + +static int read_session_pids_limit(const char *path_fmt, int uid, + void (*cleanup_fn) (void)) +{ + int max_pids, ret; + char path[PATH_MAX]; + + ret = snprintf(path, sizeof(path), path_fmt, uid); + if (ret < 0 || (size_t)ret >= sizeof(path)) + return -1; + + if (access(path, R_OK) != 0) { + tst_resm(TINFO, "Cannot read session user limits from '%s'", path); + return -1; + } + + SAFE_FILE_SCANF(cleanup_fn, path, "%d", &max_pids); + tst_resm(TINFO, "Found limit of processes %d (from %s)", max_pids, path); + + return max_pids; +} + +static int get_session_pids_limit(void (*cleanup_fn) (void)) +{ + int max_pids, uid; + + uid = get_session_uid(); + if (TEST_RETURN != 1) { + tst_resm(TINFO, "Cannot get UID"); + return -1; + } + + max_pids = read_session_pids_limit(CGROUPS_V2_SLICE_FMT, uid, cleanup_fn); + if (max_pids < 0) + max_pids = read_session_pids_limit(CGROUPS_V1_SLICE_FMT, uid, + cleanup_fn); + + if (max_pids < 0) + return -1; + + return max_pids; +} + int tst_get_free_pids_(void (*cleanup_fn) (void)) { FILE *f; - int rc, used_pids, max_pids; + int rc, used_pids, max_pids, max_session_pids; f = popen("ps -eT | wc -l", "r"); if (!f) { @@ -57,6 +130,10 @@ int tst_get_free_pids_(void (*cleanup_fn) (void)) SAFE_FILE_SCANF(cleanup_fn, PID_MAX_PATH, "%d", &max_pids); + max_session_pids = get_session_pids_limit(cleanup_fn); + if ((max_session_pids > 0) && (max_session_pids < max_pids)) + max_pids = max_session_pids; + /* max_pids contains the maximum PID + 1, * used_pids contains used PIDs + 1, * so this additional '1' is eliminated by the substraction */ -- 2.27.0