From mboxrd@z Thu Jan 1 00:00:00 1970 From: Petr Vorel Date: Mon, 28 Jun 2021 16:47:34 +0200 Subject: [LTP] [PATCH v3 2/4] syscalls/msgstress04: fix fork failure on small memory systems In-Reply-To: <20210623135912.81156-3-krzysztof.kozlowski@canonical.com> References: <20210623135912.81156-1-krzysztof.kozlowski@canonical.com> <20210623135912.81156-3-krzysztof.kozlowski@canonical.com> Message-ID: List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ltp@lists.linux.it Hi Krzysztof, nit: Instead of git commit subject "syscalls/msgstress04: fix fork failure on small memory systems". I'd use "tst_pid.c: fix fork ...". > 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)); FYI We recently decided to not use TEST() macro in library itself. See Richard's effort [1]. We should document it in LTP Library API Writing Guidelines [2] > + if (TEST_RETURN != 1) { > +#ifdef DEBUG FYI we don't support DEBUG. Either the information is always important or not. In this case I'd probably avoid printing it. > + 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) { and here as well > + tst_resm(TINFO, "Cannot get UID"); > + return -1; > + } Kind regards, Petr [1] https://patchwork.ozlabs.org/project/ltp/patch/20210621113804.26179-2-rpalethorpe@suse.com/ [2] https://github.com/linux-test-project/ltp/wiki/LTP-Library-API-Writing-Guidelines