svn commit: r367927 - in head: sys/kern tests/sys/kern
Robert Wing
rew at FreeBSD.org
Sun Nov 22 05:00:29 UTC 2020
Author: rew
Date: Sun Nov 22 05:00:28 2020
New Revision: 367927
URL: https://svnweb.freebsd.org/changeset/base/367927
Log:
fd: free old file descriptor tables when not shared
During the life of a process, new file descriptor tables may be allocated. When
a new table is allocated, the old table is placed in a free list and held onto
until all processes referencing them exit.
When a new file descriptor table is allocated, the old file descriptor table
can be freed when the current process has a single-thread and the file
descriptor table is not being shared with any other processes.
Reviewed by: kevans
Approved by: kevans (mentor)
Differential Revision: https://reviews.freebsd.org/D18617
Added:
head/tests/sys/kern/fdgrowtable_test.c (contents, props changed)
Modified:
head/sys/kern/kern_descrip.c
head/tests/sys/kern/Makefile
Modified: head/sys/kern/kern_descrip.c
==============================================================================
--- head/sys/kern/kern_descrip.c Sun Nov 22 04:29:55 2020 (r367926)
+++ head/sys/kern/kern_descrip.c Sun Nov 22 05:00:28 2020 (r367927)
@@ -1801,8 +1801,12 @@ fdgrowtable(struct filedesc *fdp, int nfd)
atomic_store_rel_ptr((volatile void *)&fdp->fd_files, (uintptr_t)ntable);
/*
- * Do not free the old file table, as some threads may still
- * reference entries within it. Instead, place it on a freelist
+ * Free the old file table when not shared by other threads or processes.
+ * The old file table is considered to be shared when either are true:
+ * - The process has more than one thread.
+ * - The file descriptor table has been shared via fdshare().
+ *
+ * When shared, the old file table will be placed on a freelist
* which will be processed when the struct filedesc is released.
*
* Note that if onfiles == NDFILE, we're dealing with the original
@@ -1810,10 +1814,14 @@ fdgrowtable(struct filedesc *fdp, int nfd)
* which must not be freed.
*/
if (onfiles > NDFILE) {
- ft = (struct freetable *)&otable->fdt_ofiles[onfiles];
- fdp0 = (struct filedesc0 *)fdp;
- ft->ft_table = otable;
- SLIST_INSERT_HEAD(&fdp0->fd_free, ft, ft_next);
+ if (curproc->p_numthreads == 1 && fdp->fd_refcnt == 1)
+ free(otable, M_FILEDESC);
+ else {
+ ft = (struct freetable *)&otable->fdt_ofiles[onfiles];
+ fdp0 = (struct filedesc0 *)fdp;
+ ft->ft_table = otable;
+ SLIST_INSERT_HEAD(&fdp0->fd_free, ft, ft_next);
+ }
}
/*
* The map does not have the same possibility of threads still
Modified: head/tests/sys/kern/Makefile
==============================================================================
--- head/tests/sys/kern/Makefile Sun Nov 22 04:29:55 2020 (r367926)
+++ head/tests/sys/kern/Makefile Sun Nov 22 05:00:28 2020 (r367927)
@@ -10,6 +10,7 @@ TESTSDIR= ${TESTSBASE}/sys/kern
#ATF_TESTS_C+= kcov
ATF_TESTS_C+= kern_copyin
ATF_TESTS_C+= kern_descrip_test
+ATF_TESTS_C+= fdgrowtable_test
ATF_TESTS_C+= kill_zombie
ATF_TESTS_C+= ptrace_test
TEST_METADATA.ptrace_test+= timeout="15"
@@ -46,6 +47,7 @@ LIBADD.ptrace_test+= pthread
LIBADD.unix_seqpacket_test+= pthread
LIBADD.kcov+= pthread
LIBADD.sendfile_helper+= pthread
+LIBADD.fdgrowtable_test+= util pthread kvm procstat
NETBSD_ATF_TESTS_C+= lockf_test
NETBSD_ATF_TESTS_C+= mqueue_test
Added: head/tests/sys/kern/fdgrowtable_test.c
==============================================================================
--- /dev/null 00:00:00 1970 (empty, because file is newly added)
+++ head/tests/sys/kern/fdgrowtable_test.c Sun Nov 22 05:00:28 2020 (r367927)
@@ -0,0 +1,267 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+ *
+ * Copyright (c) 2020 Rob Wing
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/param.h>
+#include <sys/filedesc.h>
+#include <sys/queue.h>
+#include <sys/sysctl.h>
+#include <sys/user.h>
+#include <sys/wait.h>
+
+#include <atf-c.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+/* linked libraries */
+#include <kvm.h>
+#include <libutil.h>
+#include <libprocstat.h>
+#include <pthread.h>
+
+/* test-case macro */
+#define AFILE "afile"
+
+/*
+ * The following macros, struct freetable, struct fdescenttbl0
+ * and struct filedesc0 are copied from sys/kern/kern_descrip.c
+ */
+#define NDFILE 20
+#define NDSLOTSIZE sizeof(NDSLOTTYPE)
+#define NDENTRIES (NDSLOTSIZE * __CHAR_BIT)
+#define NDSLOT(x) ((x) / NDENTRIES)
+#define NDBIT(x) ((NDSLOTTYPE)1 << ((x) % NDENTRIES))
+#define NDSLOTS(x) (((x) + NDENTRIES - 1) / NDENTRIES)
+
+struct freetable {
+ struct fdescenttbl *ft_table;
+ SLIST_ENTRY(freetable) ft_next;
+};
+
+struct fdescenttbl0 {
+ int fdt_nfiles;
+ struct filedescent fdt_ofiles[NDFILE];
+};
+
+struct filedesc0 {
+ struct filedesc fd_fd;
+ SLIST_HEAD(, freetable) fd_free;
+ struct fdescenttbl0 fd_dfiles;
+ NDSLOTTYPE fd_dmap[NDSLOTS(NDFILE)];
+};
+
+static void
+openfiles(int n)
+{
+ int i, fd;
+
+ ATF_REQUIRE((fd = open(AFILE, O_CREAT, 0644)) != -1);
+ close(fd);
+ for (i = 0; i < n; i++)
+ ATF_REQUIRE((fd = open(AFILE, O_RDONLY, 0644)) != -1);
+}
+
+/*
+ * Get a count of the old file descriptor tables on the freelist.
+ */
+static int
+old_tables(kvm_t *kd, struct kinfo_proc *kp)
+{
+ struct filedesc0 fdp0;
+ struct freetable *ft, tft;
+ int counter;
+
+ counter = 0;
+
+ ATF_REQUIRE(kvm_read(kd, (unsigned long) kp->ki_fd, &fdp0, sizeof(fdp0)) > 0);
+
+ SLIST_FOREACH(ft, &fdp0.fd_free, ft_next) {
+ ATF_REQUIRE(kvm_read(kd, (unsigned long) ft, &tft, sizeof(tft)) > 0 );
+ ft = &tft;
+ counter++;
+ }
+
+ return (counter);
+}
+
+/*
+ * The returning struct kinfo_proc stores kernel addresses that will be
+ * used by kvm_read to retrieve information for the current process.
+ */
+static struct kinfo_proc *
+read_kinfo(kvm_t *kd)
+{
+ struct kinfo_proc *kp;
+ int procs_found;
+
+ ATF_REQUIRE((kp = kvm_getprocs(kd, KERN_PROC_PID, (int) getpid(), &procs_found)) != NULL);
+ ATF_REQUIRE(procs_found == 1);
+
+ return (kp);
+}
+
+/*
+ * Test a single threaded process that doesn't have a shared
+ * file descriptor table. The old tables should be freed.
+ */
+ATF_TC(free_oldtables);
+ATF_TC_HEAD(free_oldtables, tc)
+{
+ atf_tc_set_md_var(tc, "require.user", "root");
+}
+
+ATF_TC_BODY(free_oldtables, tc)
+{
+ kvm_t *kd;
+ struct kinfo_proc *kp;
+
+ ATF_REQUIRE((kd = kvm_open(NULL, NULL, NULL, O_RDONLY, NULL)) != NULL);
+ openfiles(128);
+ kp = read_kinfo(kd);
+ ATF_CHECK(old_tables(kd,kp) == 0);
+}
+
+static void *
+exec_thread(void *args)
+{
+ for (;;)
+ sleep(1);
+}
+
+/*
+ * Test a process with two threads that doesn't have a shared file
+ * descriptor table. The old tables should not be freed.
+ */
+ATF_TC(oldtables_shared_via_threads);
+ATF_TC_HEAD(oldtables_shared_via_threads, tc)
+{
+ atf_tc_set_md_var(tc, "require.user", "root");
+}
+
+ATF_TC_BODY(oldtables_shared_via_threads, tc)
+{
+ kvm_t *kd;
+ struct kinfo_proc *kp;
+ pthread_t thread;
+
+ ATF_REQUIRE((kd = kvm_open(NULL, NULL, NULL, O_RDONLY, NULL)) != NULL);
+ ATF_REQUIRE(pthread_create(&thread, NULL, exec_thread, NULL) == 0);
+
+ openfiles(128);
+
+ kp = read_kinfo(kd);
+ ATF_CHECK(kp->ki_numthreads > 1);
+ ATF_CHECK(old_tables(kd,kp) > 1);
+
+ ATF_REQUIRE(pthread_cancel(thread) == 0);
+ ATF_REQUIRE(pthread_join(thread, NULL) == 0);
+}
+
+/*
+ * Get the reference count of a file descriptor table.
+ */
+static int
+filedesc_refcnt(kvm_t *kd, struct kinfo_proc *kp)
+{
+ struct filedesc fdp;
+
+ ATF_REQUIRE(kvm_read(kd, (unsigned long) kp->ki_fd, &fdp, sizeof(fdp)) > 0);
+
+ return (fdp.fd_refcnt);
+}
+
+/*
+ * Test a single threaded process that shares a file descriptor
+ * table with another process. The old tables should not be freed.
+ */
+ATF_TC(oldtables_shared_via_process);
+ATF_TC_HEAD(oldtables_shared_via_process, tc)
+{
+ atf_tc_set_md_var(tc, "require.user", "root");
+}
+
+ATF_TC_BODY(oldtables_shared_via_process, tc)
+{
+ kvm_t *kd;
+ struct kinfo_proc *kp;
+ int status;
+ pid_t child, wpid;
+
+ ATF_REQUIRE((kd = kvm_open(NULL, NULL, NULL, O_RDONLY, NULL)) != NULL);
+
+ /* share the file descriptor table */
+ ATF_REQUIRE((child = rfork(RFPROC)) != -1);
+
+ if (child == 0) {
+ openfiles(128);
+ raise(SIGSTOP);
+ exit(127);
+ }
+
+ /* let parent process open some files too */
+ openfiles(128);
+
+ /* get current status of child */
+ wpid = waitpid(child, &status, WUNTRACED);
+
+ /* child should be stopped */
+ ATF_REQUIRE(WIFSTOPPED(status));
+
+ /*
+ * We want to read kernel data
+ * before the child exits
+ * otherwise we'll lose a reference count
+ * to the file descriptor table
+ */
+ if (child != 0) {
+ kp = read_kinfo(kd);
+
+ ATF_CHECK(filedesc_refcnt(kd,kp) > 1);
+ ATF_CHECK(old_tables(kd,kp) > 1);
+
+ kill(child, SIGCONT);
+ }
+
+ /* child should have exited */
+ wpid = waitpid(child, &status, 0);
+ ATF_REQUIRE(WIFEXITED(status));
+ ATF_REQUIRE(WEXITSTATUS(status) == 127);
+}
+
+ATF_TP_ADD_TCS(tp)
+{
+ ATF_TP_ADD_TC(tp, free_oldtables);
+ ATF_TP_ADD_TC(tp, oldtables_shared_via_threads);
+ ATF_TP_ADD_TC(tp, oldtables_shared_via_process);
+ return (atf_no_error());
+}
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