diff --git a/lib/libc/gen/sysconf.3 b/lib/libc/gen/sysconf.3 --- a/lib/libc/gen/sysconf.3 +++ b/lib/libc/gen/sysconf.3 @@ -25,7 +25,7 @@ .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" -.Dd April 26, 2013 +.Dd August 30, 2025 .Dt SYSCONF 3 .Os .Sh NAME @@ -77,7 +77,9 @@ .It Li _SC_NPROCESSORS_CONF The number of processors configured. .It Li _SC_NPROCESSORS_ONLN -The number of processors currently online. +The number of processors currently online, taking into account current jail +restrictions to report only the number of processors that are usable to the +process. .It Li _SC_OPEN_MAX One more than the maximum value the system may assign to a new file descriptor. .It Li _SC_PAGESIZE diff --git a/lib/libc/gen/sysconf.c b/lib/libc/gen/sysconf.c --- a/lib/libc/gen/sysconf.c +++ b/lib/libc/gen/sysconf.c @@ -72,6 +72,7 @@ sysconf(int name) { struct rlimit rl; + cpuset_t cpus; size_t len; int mib[2], sverrno, value; long lvalue, defaultresult; @@ -581,8 +582,21 @@ return (_POSIX_IPV6); #endif - case _SC_NPROCESSORS_CONF: case _SC_NPROCESSORS_ONLN: + /* + * Consult our root set first, because our CPU availability + * may not match the total number of CPUs available on the + * system and we may have a non-uniform layout even within + * userland. In particular, each jail has a root set that can + * be constrained by its parent and processes within the jail + * cannot widen beyond those constraints, so to those processes + * it makes sense to claim the more limited count. + */ + if (cpuset_getaffinity(CPU_LEVEL_ROOT, CPU_WHICH_PID, -1, + sizeof(cpus), &cpus) == 0) + return (CPU_COUNT(&cpus)); + /* FALLTHROUGH */ + case _SC_NPROCESSORS_CONF: if (_elf_aux_info(AT_NCPUS, &value, sizeof(value)) == 0) return ((long)value); mib[0] = CTL_HW; diff --git a/lib/libc/tests/sys/cpuset_test.c b/lib/libc/tests/sys/cpuset_test.c --- a/lib/libc/tests/sys/cpuset_test.c +++ b/lib/libc/tests/sys/cpuset_test.c @@ -34,8 +34,10 @@ #include #include +#include #include #include +#include #include #include @@ -107,6 +109,19 @@ atf_tc_skip("Test requires %d or more cores.", ncpu); } +static void +skip_ltncpu_root(int ncpu, cpuset_t *mask) +{ + + CPU_ZERO(mask); + ATF_REQUIRE_EQ(0, cpuset_getaffinity(CPU_LEVEL_ROOT, CPU_WHICH_PID, + -1, sizeof(*mask), mask)); + if (CPU_COUNT(mask) < ncpu) { + atf_tc_skip("Test requires cpuset root with %d or more cores.", + ncpu); + } +} + ATF_TC(newset); ATF_TC_HEAD(newset, tc) { @@ -234,9 +249,8 @@ } static int -do_jail(int sock) +create_jail(void) { - struct jail_test_info info; struct iovec iov[2]; char *name; int error; @@ -250,8 +264,22 @@ iov[1].iov_base = name; iov[1].iov_len = strlen(name) + 1; - if (jail_set(iov, 2, JAIL_CREATE | JAIL_ATTACH) < 0) + error = jail_set(iov, 2, JAIL_CREATE | JAIL_ATTACH); + free(name); + if (error < 0) return (FAILURE_JAIL); + return (0); +} + +static int +do_jail(int sock) +{ + struct jail_test_info info; + int error; + + error = create_jail(); + if (error != 0) + return (error); /* Record parameters, kick them over, then make a swift exit. */ CPU_ZERO(&info.jail_tidmask); @@ -641,6 +669,111 @@ try_attach(jid, &smask); } +struct nproc_info { + long nproc_init; + long nproc_final; + long nproc_global; +}; + +ATF_TC(jail_nproc); +ATF_TC_HEAD(jail_nproc, tc) +{ + atf_tc_set_md_var(tc, "descr", + "Test that _SC_PROCESSORS_ONLN reflects jail cpuset constraints"); +} +ATF_TC_BODY(jail_nproc, tc) +{ + cpuset_t jmask; + struct nproc_info ninfo = { }; + int sockpair[2]; + cpusetid_t setid; + ssize_t readsz; + pid_t pid; + int fcpu, error, pfd, sock; + char okb = 0x7f, rcvb; + + skip_ltncpu_root(2, &jmask); + fcpu = CPU_FFS(&jmask) - 1; + + /* + * Just adjusting our affinity should not affect the number of + * processors considered online- we want to be sure that it's only + * adjusted if our jail's root set is. + */ + CPU_CLR(fcpu, &jmask); + error = cpuset_setaffinity(CPU_LEVEL_WHICH, CPU_WHICH_PID, -1, + sizeof(jmask), &jmask); + ATF_REQUIRE_EQ(0, error); + ATF_REQUIRE(sysconf(_SC_NPROCESSORS_ONLN) > CPU_COUNT(&jmask)); + + ATF_REQUIRE_EQ(0, socketpair(PF_UNIX, SOCK_STREAM, 0, sockpair)); + + /* We'll wait on the procdesc, too, so we can fail faster if it dies. */ + ATF_REQUIRE((pid = pdfork(&pfd, 0)) != -1); + + if (pid == 0) { + /* First child sets up the jail. */ + sock = sockpair[SP_CHILD]; + close(sockpair[SP_PARENT]); + + error = create_jail(); + if (error != 0) + _exit(error); + + ninfo.nproc_init = sysconf(_SC_NPROCESSORS_ONLN); + + /* Signal the parent that we're jailed. */ + readsz = write(sock, &okb, sizeof(okb)); + assert(readsz == sizeof(okb)); + + /* Wait for parent to adjust our mask and signal OK. */ + readsz = read(sock, &rcvb, sizeof(rcvb)); + assert(readsz == sizeof(rcvb)); + assert(rcvb == okb); + + ninfo.nproc_final = sysconf(_SC_NPROCESSORS_ONLN); + ninfo.nproc_global = sysconf(_SC_NPROCESSORS_CONF); + readsz = write(sock, &ninfo, sizeof(ninfo)); + assert(readsz == sizeof(ninfo)); + + _exit(0); + } + + close(sockpair[SP_CHILD]); + sock = sockpair[SP_PARENT]; + + /* Wait for signal that they are jailed. */ + readsz = read(sock, &rcvb, sizeof(rcvb)); + assert(readsz == sizeof(rcvb)); + assert(rcvb == okb); + + /* Grab the cpuset id and adjust it. */ + error = cpuset_getid(CPU_LEVEL_ROOT, CPU_WHICH_PID, pid, &setid); + ATF_REQUIRE_EQ(0, error); + error = cpuset_setaffinity(CPU_LEVEL_WHICH, CPU_WHICH_CPUSET, + setid, sizeof(jmask), &jmask); + ATF_REQUIRE_EQ(0, error); + + /* Signal OK to proceed. */ + readsz = write(sock, &okb, sizeof(okb)); + ATF_REQUIRE_EQ(sizeof(okb), readsz); + + /* Grab our final nproc info. */ + readsz = read(sock, &ninfo, sizeof(ninfo)); + ATF_REQUIRE_EQ(sizeof(ninfo), readsz); + + /* + * We set our own affinity to jmask, which is derived from *our* root + * set, at the beginning of the test. The jail would inherit from this + * set, so we just re-use that mask here to confirm that + * _SC_NPROCESSORS_ONLN did actually drop in response to us limiting the + * jail, and that its _SC_NPROCESSORS_CONF did not. + */ + ATF_REQUIRE_EQ(CPU_COUNT(&jmask) + 1, ninfo.nproc_init); + ATF_REQUIRE_EQ(CPU_COUNT(&jmask) + 1, ninfo.nproc_global); + ATF_REQUIRE_EQ(CPU_COUNT(&jmask), ninfo.nproc_final); +} + ATF_TC(badparent); ATF_TC_HEAD(badparent, tc) { @@ -686,6 +819,7 @@ ATF_TP_ADD_TC(tp, jail_attach_prevbase); ATF_TP_ADD_TC(tp, jail_attach_plain); ATF_TP_ADD_TC(tp, jail_attach_disjoint); + ATF_TP_ADD_TC(tp, jail_nproc); ATF_TP_ADD_TC(tp, badparent); return (atf_no_error()); }