summaryrefslogtreecommitdiffstats
path: root/kernel/fs/proc/array.c
diff options
context:
space:
mode:
authorYunhong Jiang <yunhong.jiang@intel.com>2015-08-04 12:17:53 -0700
committerYunhong Jiang <yunhong.jiang@intel.com>2015-08-04 15:44:42 -0700
commit9ca8dbcc65cfc63d6f5ef3312a33184e1d726e00 (patch)
tree1c9cafbcd35f783a87880a10f85d1a060db1a563 /kernel/fs/proc/array.c
parent98260f3884f4a202f9ca5eabed40b1354c489b29 (diff)
Add the rt linux 4.1.3-rt3 as base
Import the rt linux 4.1.3-rt3 as OPNFV kvm base. It's from git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git linux-4.1.y-rt and the base is: commit 0917f823c59692d751951bf5ea699a2d1e2f26a2 Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Date: Sat Jul 25 12:13:34 2015 +0200 Prepare v4.1.3-rt3 Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> We lose all the git history this way and it's not good. We should apply another opnfv project repo in future. Change-Id: I87543d81c9df70d99c5001fbdf646b202c19f423 Signed-off-by: Yunhong Jiang <yunhong.jiang@intel.com>
Diffstat (limited to 'kernel/fs/proc/array.c')
-rw-r--r--kernel/fs/proc/array.c695
1 files changed, 695 insertions, 0 deletions
diff --git a/kernel/fs/proc/array.c b/kernel/fs/proc/array.c
new file mode 100644
index 000000000..fd02a9ebf
--- /dev/null
+++ b/kernel/fs/proc/array.c
@@ -0,0 +1,695 @@
+/*
+ * linux/fs/proc/array.c
+ *
+ * Copyright (C) 1992 by Linus Torvalds
+ * based on ideas by Darren Senn
+ *
+ * Fixes:
+ * Michael. K. Johnson: stat,statm extensions.
+ * <johnsonm@stolaf.edu>
+ *
+ * Pauline Middelink : Made cmdline,envline only break at '\0's, to
+ * make sure SET_PROCTITLE works. Also removed
+ * bad '!' which forced address recalculation for
+ * EVERY character on the current page.
+ * <middelin@polyware.iaf.nl>
+ *
+ * Danny ter Haar : added cpuinfo
+ * <dth@cistron.nl>
+ *
+ * Alessandro Rubini : profile extension.
+ * <rubini@ipvvis.unipv.it>
+ *
+ * Jeff Tranter : added BogoMips field to cpuinfo
+ * <Jeff_Tranter@Mitel.COM>
+ *
+ * Bruno Haible : remove 4K limit for the maps file
+ * <haible@ma2s2.mathematik.uni-karlsruhe.de>
+ *
+ * Yves Arrouye : remove removal of trailing spaces in get_array.
+ * <Yves.Arrouye@marin.fdn.fr>
+ *
+ * Jerome Forissier : added per-CPU time information to /proc/stat
+ * and /proc/<pid>/cpu extension
+ * <forissier@isia.cma.fr>
+ * - Incorporation and non-SMP safe operation
+ * of forissier patch in 2.1.78 by
+ * Hans Marcus <crowbar@concepts.nl>
+ *
+ * aeb@cwi.nl : /proc/partitions
+ *
+ *
+ * Alan Cox : security fixes.
+ * <alan@lxorguk.ukuu.org.uk>
+ *
+ * Al Viro : safe handling of mm_struct
+ *
+ * Gerhard Wichert : added BIGMEM support
+ * Siemens AG <Gerhard.Wichert@pdb.siemens.de>
+ *
+ * Al Viro & Jeff Garzik : moved most of the thing into base.c and
+ * : proc_misc.c. The rest may eventually go into
+ * : base.c too.
+ */
+
+#include <linux/types.h>
+#include <linux/errno.h>
+#include <linux/time.h>
+#include <linux/kernel.h>
+#include <linux/kernel_stat.h>
+#include <linux/tty.h>
+#include <linux/string.h>
+#include <linux/mman.h>
+#include <linux/proc_fs.h>
+#include <linux/ioport.h>
+#include <linux/uaccess.h>
+#include <linux/io.h>
+#include <linux/mm.h>
+#include <linux/hugetlb.h>
+#include <linux/pagemap.h>
+#include <linux/swap.h>
+#include <linux/smp.h>
+#include <linux/signal.h>
+#include <linux/highmem.h>
+#include <linux/file.h>
+#include <linux/fdtable.h>
+#include <linux/times.h>
+#include <linux/cpuset.h>
+#include <linux/rcupdate.h>
+#include <linux/delayacct.h>
+#include <linux/seq_file.h>
+#include <linux/pid_namespace.h>
+#include <linux/ptrace.h>
+#include <linux/tracehook.h>
+#include <linux/string_helpers.h>
+#include <linux/user_namespace.h>
+
+#include <asm/pgtable.h>
+#include <asm/processor.h>
+#include "internal.h"
+
+static inline void task_name(struct seq_file *m, struct task_struct *p)
+{
+ char *buf;
+ char tcomm[sizeof(p->comm)];
+
+ get_task_comm(tcomm, p);
+
+ seq_puts(m, "Name:\t");
+ buf = m->buf + m->count;
+
+ /* Ignore error for now */
+ buf += string_escape_str(tcomm, buf, m->size - m->count,
+ ESCAPE_SPACE | ESCAPE_SPECIAL, "\n\\");
+
+ m->count = buf - m->buf;
+ seq_putc(m, '\n');
+}
+
+/*
+ * The task state array is a strange "bitmap" of
+ * reasons to sleep. Thus "running" is zero, and
+ * you can test for combinations of others with
+ * simple bit tests.
+ */
+static const char * const task_state_array[] = {
+ "R (running)", /* 0 */
+ "S (sleeping)", /* 1 */
+ "D (disk sleep)", /* 2 */
+ "T (stopped)", /* 4 */
+ "t (tracing stop)", /* 8 */
+ "X (dead)", /* 16 */
+ "Z (zombie)", /* 32 */
+};
+
+static inline const char *get_task_state(struct task_struct *tsk)
+{
+ unsigned int state = (tsk->state | tsk->exit_state) & TASK_REPORT;
+
+ BUILD_BUG_ON(1 + ilog2(TASK_REPORT) != ARRAY_SIZE(task_state_array)-1);
+
+ return task_state_array[fls(state)];
+}
+
+static inline void task_state(struct seq_file *m, struct pid_namespace *ns,
+ struct pid *pid, struct task_struct *p)
+{
+ struct user_namespace *user_ns = seq_user_ns(m);
+ struct group_info *group_info;
+ int g;
+ struct task_struct *tracer;
+ const struct cred *cred;
+ pid_t ppid, tpid = 0, tgid, ngid;
+ unsigned int max_fds = 0;
+
+ rcu_read_lock();
+ ppid = pid_alive(p) ?
+ task_tgid_nr_ns(rcu_dereference(p->real_parent), ns) : 0;
+
+ tracer = ptrace_parent(p);
+ if (tracer)
+ tpid = task_pid_nr_ns(tracer, ns);
+
+ tgid = task_tgid_nr_ns(p, ns);
+ ngid = task_numa_group_id(p);
+ cred = get_task_cred(p);
+
+ task_lock(p);
+ if (p->files)
+ max_fds = files_fdtable(p->files)->max_fds;
+ task_unlock(p);
+ rcu_read_unlock();
+
+ seq_printf(m,
+ "State:\t%s\n"
+ "Tgid:\t%d\n"
+ "Ngid:\t%d\n"
+ "Pid:\t%d\n"
+ "PPid:\t%d\n"
+ "TracerPid:\t%d\n"
+ "Uid:\t%d\t%d\t%d\t%d\n"
+ "Gid:\t%d\t%d\t%d\t%d\n"
+ "FDSize:\t%d\nGroups:\t",
+ get_task_state(p),
+ tgid, ngid, pid_nr_ns(pid, ns), ppid, tpid,
+ from_kuid_munged(user_ns, cred->uid),
+ from_kuid_munged(user_ns, cred->euid),
+ from_kuid_munged(user_ns, cred->suid),
+ from_kuid_munged(user_ns, cred->fsuid),
+ from_kgid_munged(user_ns, cred->gid),
+ from_kgid_munged(user_ns, cred->egid),
+ from_kgid_munged(user_ns, cred->sgid),
+ from_kgid_munged(user_ns, cred->fsgid),
+ max_fds);
+
+ group_info = cred->group_info;
+ for (g = 0; g < group_info->ngroups; g++)
+ seq_printf(m, "%d ",
+ from_kgid_munged(user_ns, GROUP_AT(group_info, g)));
+ put_cred(cred);
+
+#ifdef CONFIG_PID_NS
+ seq_puts(m, "\nNStgid:");
+ for (g = ns->level; g <= pid->level; g++)
+ seq_printf(m, "\t%d",
+ task_tgid_nr_ns(p, pid->numbers[g].ns));
+ seq_puts(m, "\nNSpid:");
+ for (g = ns->level; g <= pid->level; g++)
+ seq_printf(m, "\t%d",
+ task_pid_nr_ns(p, pid->numbers[g].ns));
+ seq_puts(m, "\nNSpgid:");
+ for (g = ns->level; g <= pid->level; g++)
+ seq_printf(m, "\t%d",
+ task_pgrp_nr_ns(p, pid->numbers[g].ns));
+ seq_puts(m, "\nNSsid:");
+ for (g = ns->level; g <= pid->level; g++)
+ seq_printf(m, "\t%d",
+ task_session_nr_ns(p, pid->numbers[g].ns));
+#endif
+ seq_putc(m, '\n');
+}
+
+void render_sigset_t(struct seq_file *m, const char *header,
+ sigset_t *set)
+{
+ int i;
+
+ seq_puts(m, header);
+
+ i = _NSIG;
+ do {
+ int x = 0;
+
+ i -= 4;
+ if (sigismember(set, i+1)) x |= 1;
+ if (sigismember(set, i+2)) x |= 2;
+ if (sigismember(set, i+3)) x |= 4;
+ if (sigismember(set, i+4)) x |= 8;
+ seq_printf(m, "%x", x);
+ } while (i >= 4);
+
+ seq_putc(m, '\n');
+}
+
+static void collect_sigign_sigcatch(struct task_struct *p, sigset_t *ign,
+ sigset_t *catch)
+{
+ struct k_sigaction *k;
+ int i;
+
+ k = p->sighand->action;
+ for (i = 1; i <= _NSIG; ++i, ++k) {
+ if (k->sa.sa_handler == SIG_IGN)
+ sigaddset(ign, i);
+ else if (k->sa.sa_handler != SIG_DFL)
+ sigaddset(catch, i);
+ }
+}
+
+static inline void task_sig(struct seq_file *m, struct task_struct *p)
+{
+ unsigned long flags;
+ sigset_t pending, shpending, blocked, ignored, caught;
+ int num_threads = 0;
+ unsigned long qsize = 0;
+ unsigned long qlim = 0;
+
+ sigemptyset(&pending);
+ sigemptyset(&shpending);
+ sigemptyset(&blocked);
+ sigemptyset(&ignored);
+ sigemptyset(&caught);
+
+ if (lock_task_sighand(p, &flags)) {
+ pending = p->pending.signal;
+ shpending = p->signal->shared_pending.signal;
+ blocked = p->blocked;
+ collect_sigign_sigcatch(p, &ignored, &caught);
+ num_threads = get_nr_threads(p);
+ rcu_read_lock(); /* FIXME: is this correct? */
+ qsize = atomic_read(&__task_cred(p)->user->sigpending);
+ rcu_read_unlock();
+ qlim = task_rlimit(p, RLIMIT_SIGPENDING);
+ unlock_task_sighand(p, &flags);
+ }
+
+ seq_printf(m, "Threads:\t%d\n", num_threads);
+ seq_printf(m, "SigQ:\t%lu/%lu\n", qsize, qlim);
+
+ /* render them all */
+ render_sigset_t(m, "SigPnd:\t", &pending);
+ render_sigset_t(m, "ShdPnd:\t", &shpending);
+ render_sigset_t(m, "SigBlk:\t", &blocked);
+ render_sigset_t(m, "SigIgn:\t", &ignored);
+ render_sigset_t(m, "SigCgt:\t", &caught);
+}
+
+static void render_cap_t(struct seq_file *m, const char *header,
+ kernel_cap_t *a)
+{
+ unsigned __capi;
+
+ seq_puts(m, header);
+ CAP_FOR_EACH_U32(__capi) {
+ seq_printf(m, "%08x",
+ a->cap[CAP_LAST_U32 - __capi]);
+ }
+ seq_putc(m, '\n');
+}
+
+static inline void task_cap(struct seq_file *m, struct task_struct *p)
+{
+ const struct cred *cred;
+ kernel_cap_t cap_inheritable, cap_permitted, cap_effective, cap_bset;
+
+ rcu_read_lock();
+ cred = __task_cred(p);
+ cap_inheritable = cred->cap_inheritable;
+ cap_permitted = cred->cap_permitted;
+ cap_effective = cred->cap_effective;
+ cap_bset = cred->cap_bset;
+ rcu_read_unlock();
+
+ render_cap_t(m, "CapInh:\t", &cap_inheritable);
+ render_cap_t(m, "CapPrm:\t", &cap_permitted);
+ render_cap_t(m, "CapEff:\t", &cap_effective);
+ render_cap_t(m, "CapBnd:\t", &cap_bset);
+}
+
+static inline void task_seccomp(struct seq_file *m, struct task_struct *p)
+{
+#ifdef CONFIG_SECCOMP
+ seq_printf(m, "Seccomp:\t%d\n", p->seccomp.mode);
+#endif
+}
+
+static inline void task_context_switch_counts(struct seq_file *m,
+ struct task_struct *p)
+{
+ seq_printf(m, "voluntary_ctxt_switches:\t%lu\n"
+ "nonvoluntary_ctxt_switches:\t%lu\n",
+ p->nvcsw,
+ p->nivcsw);
+}
+
+static void task_cpus_allowed(struct seq_file *m, struct task_struct *task)
+{
+ seq_printf(m, "Cpus_allowed:\t%*pb\n",
+ cpumask_pr_args(&task->cpus_allowed));
+ seq_printf(m, "Cpus_allowed_list:\t%*pbl\n",
+ cpumask_pr_args(&task->cpus_allowed));
+}
+
+int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,
+ struct pid *pid, struct task_struct *task)
+{
+ struct mm_struct *mm = get_task_mm(task);
+
+ task_name(m, task);
+ task_state(m, ns, pid, task);
+
+ if (mm) {
+ task_mem(m, mm);
+ mmput(mm);
+ }
+ task_sig(m, task);
+ task_cap(m, task);
+ task_seccomp(m, task);
+ task_cpus_allowed(m, task);
+ cpuset_task_status_allowed(m, task);
+ task_context_switch_counts(m, task);
+ return 0;
+}
+
+static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
+ struct pid *pid, struct task_struct *task, int whole)
+{
+ unsigned long vsize, eip, esp, wchan = ~0UL;
+ int priority, nice;
+ int tty_pgrp = -1, tty_nr = 0;
+ sigset_t sigign, sigcatch;
+ char state;
+ pid_t ppid = 0, pgid = -1, sid = -1;
+ int num_threads = 0;
+ int permitted;
+ struct mm_struct *mm;
+ unsigned long long start_time;
+ unsigned long cmin_flt = 0, cmaj_flt = 0;
+ unsigned long min_flt = 0, maj_flt = 0;
+ cputime_t cutime, cstime, utime, stime;
+ cputime_t cgtime, gtime;
+ unsigned long rsslim = 0;
+ char tcomm[sizeof(task->comm)];
+ unsigned long flags;
+
+ state = *get_task_state(task);
+ vsize = eip = esp = 0;
+ permitted = ptrace_may_access(task, PTRACE_MODE_READ | PTRACE_MODE_NOAUDIT);
+ mm = get_task_mm(task);
+ if (mm) {
+ vsize = task_vsize(mm);
+ if (permitted) {
+ eip = KSTK_EIP(task);
+ esp = KSTK_ESP(task);
+ }
+ }
+
+ get_task_comm(tcomm, task);
+
+ sigemptyset(&sigign);
+ sigemptyset(&sigcatch);
+ cutime = cstime = utime = stime = 0;
+ cgtime = gtime = 0;
+
+ if (lock_task_sighand(task, &flags)) {
+ struct signal_struct *sig = task->signal;
+
+ if (sig->tty) {
+ struct pid *pgrp = tty_get_pgrp(sig->tty);
+ tty_pgrp = pid_nr_ns(pgrp, ns);
+ put_pid(pgrp);
+ tty_nr = new_encode_dev(tty_devnum(sig->tty));
+ }
+
+ num_threads = get_nr_threads(task);
+ collect_sigign_sigcatch(task, &sigign, &sigcatch);
+
+ cmin_flt = sig->cmin_flt;
+ cmaj_flt = sig->cmaj_flt;
+ cutime = sig->cutime;
+ cstime = sig->cstime;
+ cgtime = sig->cgtime;
+ rsslim = ACCESS_ONCE(sig->rlim[RLIMIT_RSS].rlim_cur);
+
+ /* add up live thread stats at the group level */
+ if (whole) {
+ struct task_struct *t = task;
+ do {
+ min_flt += t->min_flt;
+ maj_flt += t->maj_flt;
+ gtime += task_gtime(t);
+ } while_each_thread(task, t);
+
+ min_flt += sig->min_flt;
+ maj_flt += sig->maj_flt;
+ thread_group_cputime_adjusted(task, &utime, &stime);
+ gtime += sig->gtime;
+ }
+
+ sid = task_session_nr_ns(task, ns);
+ ppid = task_tgid_nr_ns(task->real_parent, ns);
+ pgid = task_pgrp_nr_ns(task, ns);
+
+ unlock_task_sighand(task, &flags);
+ }
+
+ if (permitted && (!whole || num_threads < 2))
+ wchan = get_wchan(task);
+ if (!whole) {
+ min_flt = task->min_flt;
+ maj_flt = task->maj_flt;
+ task_cputime_adjusted(task, &utime, &stime);
+ gtime = task_gtime(task);
+ }
+
+ /* scale priority and nice values from timeslices to -20..20 */
+ /* to make it look like a "normal" Unix priority/nice value */
+ priority = task_prio(task);
+ nice = task_nice(task);
+
+ /* convert nsec -> ticks */
+ start_time = nsec_to_clock_t(task->real_start_time);
+
+ seq_printf(m, "%d (%s) %c", pid_nr_ns(pid, ns), tcomm, state);
+ seq_put_decimal_ll(m, ' ', ppid);
+ seq_put_decimal_ll(m, ' ', pgid);
+ seq_put_decimal_ll(m, ' ', sid);
+ seq_put_decimal_ll(m, ' ', tty_nr);
+ seq_put_decimal_ll(m, ' ', tty_pgrp);
+ seq_put_decimal_ull(m, ' ', task->flags);
+ seq_put_decimal_ull(m, ' ', min_flt);
+ seq_put_decimal_ull(m, ' ', cmin_flt);
+ seq_put_decimal_ull(m, ' ', maj_flt);
+ seq_put_decimal_ull(m, ' ', cmaj_flt);
+ seq_put_decimal_ull(m, ' ', cputime_to_clock_t(utime));
+ seq_put_decimal_ull(m, ' ', cputime_to_clock_t(stime));
+ seq_put_decimal_ll(m, ' ', cputime_to_clock_t(cutime));
+ seq_put_decimal_ll(m, ' ', cputime_to_clock_t(cstime));
+ seq_put_decimal_ll(m, ' ', priority);
+ seq_put_decimal_ll(m, ' ', nice);
+ seq_put_decimal_ll(m, ' ', num_threads);
+ seq_put_decimal_ull(m, ' ', 0);
+ seq_put_decimal_ull(m, ' ', start_time);
+ seq_put_decimal_ull(m, ' ', vsize);
+ seq_put_decimal_ull(m, ' ', mm ? get_mm_rss(mm) : 0);
+ seq_put_decimal_ull(m, ' ', rsslim);
+ seq_put_decimal_ull(m, ' ', mm ? (permitted ? mm->start_code : 1) : 0);
+ seq_put_decimal_ull(m, ' ', mm ? (permitted ? mm->end_code : 1) : 0);
+ seq_put_decimal_ull(m, ' ', (permitted && mm) ? mm->start_stack : 0);
+ seq_put_decimal_ull(m, ' ', esp);
+ seq_put_decimal_ull(m, ' ', eip);
+ /* The signal information here is obsolete.
+ * It must be decimal for Linux 2.0 compatibility.
+ * Use /proc/#/status for real-time signals.
+ */
+ seq_put_decimal_ull(m, ' ', task->pending.signal.sig[0] & 0x7fffffffUL);
+ seq_put_decimal_ull(m, ' ', task->blocked.sig[0] & 0x7fffffffUL);
+ seq_put_decimal_ull(m, ' ', sigign.sig[0] & 0x7fffffffUL);
+ seq_put_decimal_ull(m, ' ', sigcatch.sig[0] & 0x7fffffffUL);
+ seq_put_decimal_ull(m, ' ', wchan);
+ seq_put_decimal_ull(m, ' ', 0);
+ seq_put_decimal_ull(m, ' ', 0);
+ seq_put_decimal_ll(m, ' ', task->exit_signal);
+ seq_put_decimal_ll(m, ' ', task_cpu(task));
+ seq_put_decimal_ull(m, ' ', task->rt_priority);
+ seq_put_decimal_ull(m, ' ', task->policy);
+ seq_put_decimal_ull(m, ' ', delayacct_blkio_ticks(task));
+ seq_put_decimal_ull(m, ' ', cputime_to_clock_t(gtime));
+ seq_put_decimal_ll(m, ' ', cputime_to_clock_t(cgtime));
+
+ if (mm && permitted) {
+ seq_put_decimal_ull(m, ' ', mm->start_data);
+ seq_put_decimal_ull(m, ' ', mm->end_data);
+ seq_put_decimal_ull(m, ' ', mm->start_brk);
+ seq_put_decimal_ull(m, ' ', mm->arg_start);
+ seq_put_decimal_ull(m, ' ', mm->arg_end);
+ seq_put_decimal_ull(m, ' ', mm->env_start);
+ seq_put_decimal_ull(m, ' ', mm->env_end);
+ } else
+ seq_printf(m, " 0 0 0 0 0 0 0");
+
+ if (permitted)
+ seq_put_decimal_ll(m, ' ', task->exit_code);
+ else
+ seq_put_decimal_ll(m, ' ', 0);
+
+ seq_putc(m, '\n');
+ if (mm)
+ mmput(mm);
+ return 0;
+}
+
+int proc_tid_stat(struct seq_file *m, struct pid_namespace *ns,
+ struct pid *pid, struct task_struct *task)
+{
+ return do_task_stat(m, ns, pid, task, 0);
+}
+
+int proc_tgid_stat(struct seq_file *m, struct pid_namespace *ns,
+ struct pid *pid, struct task_struct *task)
+{
+ return do_task_stat(m, ns, pid, task, 1);
+}
+
+int proc_pid_statm(struct seq_file *m, struct pid_namespace *ns,
+ struct pid *pid, struct task_struct *task)
+{
+ unsigned long size = 0, resident = 0, shared = 0, text = 0, data = 0;
+ struct mm_struct *mm = get_task_mm(task);
+
+ if (mm) {
+ size = task_statm(mm, &shared, &text, &data, &resident);
+ mmput(mm);
+ }
+ /*
+ * For quick read, open code by putting numbers directly
+ * expected format is
+ * seq_printf(m, "%lu %lu %lu %lu 0 %lu 0\n",
+ * size, resident, shared, text, data);
+ */
+ seq_put_decimal_ull(m, 0, size);
+ seq_put_decimal_ull(m, ' ', resident);
+ seq_put_decimal_ull(m, ' ', shared);
+ seq_put_decimal_ull(m, ' ', text);
+ seq_put_decimal_ull(m, ' ', 0);
+ seq_put_decimal_ull(m, ' ', data);
+ seq_put_decimal_ull(m, ' ', 0);
+ seq_putc(m, '\n');
+
+ return 0;
+}
+
+#ifdef CONFIG_CHECKPOINT_RESTORE
+static struct pid *
+get_children_pid(struct inode *inode, struct pid *pid_prev, loff_t pos)
+{
+ struct task_struct *start, *task;
+ struct pid *pid = NULL;
+
+ read_lock(&tasklist_lock);
+
+ start = pid_task(proc_pid(inode), PIDTYPE_PID);
+ if (!start)
+ goto out;
+
+ /*
+ * Lets try to continue searching first, this gives
+ * us significant speedup on children-rich processes.
+ */
+ if (pid_prev) {
+ task = pid_task(pid_prev, PIDTYPE_PID);
+ if (task && task->real_parent == start &&
+ !(list_empty(&task->sibling))) {
+ if (list_is_last(&task->sibling, &start->children))
+ goto out;
+ task = list_first_entry(&task->sibling,
+ struct task_struct, sibling);
+ pid = get_pid(task_pid(task));
+ goto out;
+ }
+ }
+
+ /*
+ * Slow search case.
+ *
+ * We might miss some children here if children
+ * are exited while we were not holding the lock,
+ * but it was never promised to be accurate that
+ * much.
+ *
+ * "Just suppose that the parent sleeps, but N children
+ * exit after we printed their tids. Now the slow paths
+ * skips N extra children, we miss N tasks." (c)
+ *
+ * So one need to stop or freeze the leader and all
+ * its children to get a precise result.
+ */
+ list_for_each_entry(task, &start->children, sibling) {
+ if (pos-- == 0) {
+ pid = get_pid(task_pid(task));
+ break;
+ }
+ }
+
+out:
+ read_unlock(&tasklist_lock);
+ return pid;
+}
+
+static int children_seq_show(struct seq_file *seq, void *v)
+{
+ struct inode *inode = seq->private;
+ pid_t pid;
+
+ pid = pid_nr_ns(v, inode->i_sb->s_fs_info);
+ seq_printf(seq, "%d ", pid);
+
+ return 0;
+}
+
+static void *children_seq_start(struct seq_file *seq, loff_t *pos)
+{
+ return get_children_pid(seq->private, NULL, *pos);
+}
+
+static void *children_seq_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+ struct pid *pid;
+
+ pid = get_children_pid(seq->private, v, *pos + 1);
+ put_pid(v);
+
+ ++*pos;
+ return pid;
+}
+
+static void children_seq_stop(struct seq_file *seq, void *v)
+{
+ put_pid(v);
+}
+
+static const struct seq_operations children_seq_ops = {
+ .start = children_seq_start,
+ .next = children_seq_next,
+ .stop = children_seq_stop,
+ .show = children_seq_show,
+};
+
+static int children_seq_open(struct inode *inode, struct file *file)
+{
+ struct seq_file *m;
+ int ret;
+
+ ret = seq_open(file, &children_seq_ops);
+ if (ret)
+ return ret;
+
+ m = file->private_data;
+ m->private = inode;
+
+ return ret;
+}
+
+int children_seq_release(struct inode *inode, struct file *file)
+{
+ seq_release(inode, file);
+ return 0;
+}
+
+const struct file_operations proc_tid_children_operations = {
+ .open = children_seq_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = children_seq_release,
+};
+#endif /* CONFIG_CHECKPOINT_RESTORE */