[PATCH 2/5] introduce "struct wait_opts" to simplify do_wait() pathes

Oleg Nesterov
2009-05-07T06:51:50Z

Introduce "struct wait_opts" which holds the parameters for misc helpers
in do_wait() pathes.

This adds 13 lines to kernel/exit.c, but saves 256 bytes from .o and imho
makes the code much more readable.

This patch temporary uglifies rusage/siginfo code a little bit, will be
addressed by further cleanups.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Ingo Molnar <mingo@elte.hu>
---

kernel/exit.c | 207 ++++++++++++++++++++++++++++++----------------------------
1 file changed, 110 insertions(+), 97 deletions(-)

--- PTRACE/kernel/exit.c~2_WOPTS 2009-05-07 04:32:08.000000000 +0200
+++ PTRACE/kernel/exit.c 2009-05-07 04:37:49.000000000 +0200
@@ -1076,6 +1076,18 @@ SYSCALL_DEFINE1(exit_group, int, error_c
return 0;
}

+struct wait_opts {
+ enum pid_type wo_type;
+ struct pid *wo_pid;
+ int wo_flags;
+
+ struct siginfo __user *wo_info;
+ int __user *wo_stat;
+ struct rusage __user *wo_rusage;
+
+ int notask_error;
+};
+
static struct pid *task_pid_type(struct task_struct *task, enum pid_type type)
{
struct pid *pid = NULL;
@@ -1086,13 +1098,12 @@ static struct pid *task_pid_type(struct
return pid;
}

-static int eligible_child(enum pid_type type, struct pid *pid, int options,
- struct task_struct *p)
+static int eligible_child(struct wait_opts *wo, struct task_struct *p)
{
int err;

- if (type < PIDTYPE_MAX) {
- if (task_pid_type(p, type) != pid)
+ if (wo->wo_type < PIDTYPE_MAX) {
+ if (task_pid_type(p, wo->wo_type) != wo->wo_pid)
return 0;
}

@@ -1101,8 +1112,8 @@ static int eligible_child(enum pid_type
* set; otherwise, wait for non-clone children *only*. (Note:
* A "clone" child here is one that reports to its parent
* using a signal other than SIGCHLD.) */
- if (((p->exit_signal != SIGCHLD) ^ ((options & __WCLONE) != 0))
- && !(options & __WALL))
+ if (((p->exit_signal != SIGCHLD) ^ !!(wo->wo_flags & __WCLONE))
+ && !(wo->wo_flags & __WALL))
return 0;

err = security_task_wait(p);
@@ -1112,14 +1123,15 @@ static int eligible_child(enum pid_type
return 1;
}

-static int wait_noreap_copyout(struct task_struct *p, pid_t pid, uid_t uid,
- int why, int status,
- struct siginfo __user *infop,
- struct rusage __user *rusagep)
+static int wait_noreap_copyout(struct wait_opts *wo, struct task_struct *p,
+ pid_t pid, uid_t uid, int why, int status)
{
- int retval = rusagep ? getrusage(p, RUSAGE_BOTH, rusagep) : 0;
+ struct siginfo __user *infop;
+ int retval = wo->wo_rusage
+ ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;

put_task_struct(p);
+ infop = wo->wo_info;
if (!retval)
retval = put_user(SIGCHLD, &infop->si_signo);
if (!retval)
@@ -1143,19 +1155,18 @@ static int wait_noreap_copyout(struct ta
* the lock and this task is uninteresting. If we return nonzero, we have
* released the lock and the system call should return.
*/
-static int wait_task_zombie(struct task_struct *p, int options,
- struct siginfo __user *infop,
- int __user *stat_addr, struct rusage __user *ru)
+static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
{
unsigned long state;
int retval, status, traced;
pid_t pid = task_pid_vnr(p);
uid_t uid = __task_cred(p)->uid;
+ struct siginfo __user *infop;

- if (!likely(options & WEXITED))
+ if (!likely(wo->wo_flags & WEXITED))
return 0;

- if (unlikely(options & WNOWAIT)) {
+ if (unlikely(wo->wo_flags & WNOWAIT)) {
int exit_code = p->exit_code;
int why, status;

@@ -1168,8 +1179,7 @@ static int wait_task_zombie(struct task_
why = (exit_code & 0x80) ? CLD_DUMPED : CLD_KILLED;
status = exit_code & 0x7f;
}
- return wait_noreap_copyout(p, pid, uid, why,
- status, infop, ru);
+ return wait_noreap_copyout(wo, p, pid, uid, why, status);
}

/*
@@ -1250,11 +1260,14 @@ static int wait_task_zombie(struct task_
*/
read_unlock(&tasklist_lock);

- retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
+ retval = wo->wo_rusage
+ ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
status = (p->signal->flags & SIGNAL_GROUP_EXIT)
? p->signal->group_exit_code : p->exit_code;
- if (!retval && stat_addr)
- retval = put_user(status, stat_addr);
+ if (!retval && wo->wo_stat)
+ retval = put_user(status, wo->wo_stat);
+
+ infop = wo->wo_info;
if (!retval && infop)
retval = put_user(SIGCHLD, &infop->si_signo);
if (!retval && infop)
@@ -1322,10 +1335,10 @@ static int *task_stopped_code(struct tas
* the lock and this task is uninteresting. If we return nonzero, we have
* released the lock and the system call should return.
*/
-static int wait_task_stopped(int ptrace, struct task_struct *p,
- int options, struct siginfo __user *infop,
- int __user *stat_addr, struct rusage __user *ru)
+static int wait_task_stopped(struct wait_opts *wo,
+ int ptrace, struct task_struct *p)
{
+ struct siginfo __user *infop;
int retval, exit_code, *p_code, why;
uid_t uid = 0; /* unneeded, required by compiler */
pid_t pid;
@@ -1333,7 +1346,7 @@ static int wait_task_stopped(int ptrace,
/*
* Traditionally we see ptrace'd stopped tasks regardless of options.
*/
- if (!ptrace && !(options & WUNTRACED))
+ if (!ptrace && !(wo->wo_flags & WUNTRACED))
return 0;

exit_code = 0;
@@ -1347,7 +1360,7 @@ static int wait_task_stopped(int ptrace,
if (!exit_code)
goto unlock_sig;

- if (!unlikely(options & WNOWAIT))
+ if (!unlikely(wo->wo_flags & WNOWAIT))
*p_code = 0;

/* don't need the RCU readlock here as we're holding a spinlock */
@@ -1369,14 +1382,15 @@ unlock_sig:
why = ptrace ? CLD_TRAPPED : CLD_STOPPED;
read_unlock(&tasklist_lock);

- if (unlikely(options & WNOWAIT))
- return wait_noreap_copyout(p, pid, uid,
- why, exit_code,
- infop, ru);
+ if (unlikely(wo->wo_flags & WNOWAIT))
+ return wait_noreap_copyout(wo, p, pid, uid, why, exit_code);

- retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
- if (!retval && stat_addr)
- retval = put_user((exit_code << 8) | 0x7f, stat_addr);
+ retval = wo->wo_rusage
+ ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
+ if (!retval && wo->wo_stat)
+ retval = put_user((exit_code << 8) | 0x7f, wo->wo_stat);
+
+ infop = wo->wo_info;
if (!retval && infop)
retval = put_user(SIGCHLD, &infop->si_signo);
if (!retval && infop)
@@ -1403,15 +1417,13 @@ unlock_sig:
* the lock and this task is uninteresting. If we return nonzero, we have
* released the lock and the system call should return.
*/
-static int wait_task_continued(struct task_struct *p, int options,
- struct siginfo __user *infop,
- int __user *stat_addr, struct rusage __user *ru)
+static int wait_task_continued(struct wait_opts *wo, struct task_struct *p)
{
int retval;
pid_t pid;
uid_t uid;

- if (!unlikely(options & WCONTINUED))
+ if (!unlikely(wo->wo_flags & WCONTINUED))
return 0;

if (!(p->signal->flags & SIGNAL_STOP_CONTINUED))
@@ -1423,7 +1435,7 @@ static int wait_task_continued(struct ta
spin_unlock_irq(&p->sighand->siglock);
return 0;
}
- if (!unlikely(options & WNOWAIT))
+ if (!unlikely(wo->wo_flags & WNOWAIT))
p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
uid = __task_cred(p)->uid;
spin_unlock_irq(&p->sighand->siglock);
@@ -1432,17 +1444,17 @@ static int wait_task_continued(struct ta
get_task_struct(p);
read_unlock(&tasklist_lock);

- if (!infop) {
- retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
+ if (!wo->wo_info) {
+ retval = wo->wo_rusage
+ ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
put_task_struct(p);
- if (!retval && stat_addr)
- retval = put_user(0xffff, stat_addr);
+ if (!retval && wo->wo_stat)
+ retval = put_user(0xffff, wo->wo_stat);
if (!retval)
retval = pid;
} else {
- retval = wait_noreap_copyout(p, pid, uid,
- CLD_CONTINUED, SIGCONT,
- infop, ru);
+ retval = wait_noreap_copyout(wo, p, pid, uid,
+ CLD_CONTINUED, SIGCONT);
BUG_ON(retval == 0);
}

@@ -1452,19 +1464,16 @@ static int wait_task_continued(struct ta
/*
* Consider @p for a wait by @parent.
*
- * -ECHILD should be in *@notask_error before the first call.
+ * -ECHILD should be in ->notask_error before the first call.
* Returns nonzero for a final return, when we have unlocked tasklist_lock.
* Returns zero if the search for a child should continue;
- * then *@notask_error is 0 if @p is an eligible child,
+ * then ->notask_error is 0 if @p is an eligible child,
* or another error from security_task_wait(), or still -ECHILD.
*/
-static int wait_consider_task(struct task_struct *parent, int ptrace,
- struct task_struct *p, int *notask_error,
- enum pid_type type, struct pid *pid, int options,
- struct siginfo __user *infop,
- int __user *stat_addr, struct rusage __user *ru)
+static int wait_consider_task(struct wait_opts *wo, struct task_struct *parent,
+ int ptrace, struct task_struct *p)
{
- int ret = eligible_child(type, pid, options, p);
+ int ret = eligible_child(wo, p);
if (!ret)
return ret;

@@ -1476,8 +1485,8 @@ static int wait_consider_task(struct tas
* to look for security policy problems, rather
* than for mysterious wait bugs.
*/
- if (*notask_error)
- *notask_error = ret;
+ if (wo->notask_error)
+ wo->notask_error = ret;
return 0;
}

@@ -1486,7 +1495,7 @@ static int wait_consider_task(struct tas
* This child is hidden by ptrace.
* We aren't allowed to see it now, but eventually we will.
*/
- *notask_error = 0;
+ wo->notask_error = 0;
return 0;
}

@@ -1497,34 +1506,30 @@ static int wait_consider_task(struct tas
* We don't reap group leaders with subthreads.
*/
if (p->exit_state == EXIT_ZOMBIE && !delay_group_leader(p))
- return wait_task_zombie(p, options, infop, stat_addr, ru);
+ return wait_task_zombie(wo, p);

/*
* It's stopped or running now, so it might
* later continue, exit, or stop again.
*/
- *notask_error = 0;
+ wo->notask_error = 0;

if (task_stopped_code(p, ptrace))
- return wait_task_stopped(ptrace, p, options,
- infop, stat_addr, ru);
+ return wait_task_stopped(wo, ptrace, p);

- return wait_task_continued(p, options, infop, stat_addr, ru);
+ return wait_task_continued(wo, p);
}

/*
* Do the work of do_wait() for one thread in the group, @tsk.
*
- * -ECHILD should be in *@notask_error before the first call.
+ * -ECHILD should be in ->notask_error before the first call.
* Returns nonzero for a final return, when we have unlocked tasklist_lock.
* Returns zero if the search for a child should continue; then
- * *@notask_error is 0 if there were any eligible children,
+ * ->notask_error is 0 if there were any eligible children,
* or another error from security_task_wait(), or still -ECHILD.
*/
-static int do_wait_thread(struct task_struct *tsk, int *notask_error,
- enum pid_type type, struct pid *pid, int options,
- struct siginfo __user *infop, int __user *stat_addr,
- struct rusage __user *ru)
+static int do_wait_thread(struct wait_opts *wo, struct task_struct *tsk)
{
struct task_struct *p;

@@ -1533,9 +1538,7 @@ static int do_wait_thread(struct task_st
* Do not consider detached threads.
*/
if (!task_detached(p)) {
- int ret = wait_consider_task(tsk, 0, p, notask_error,
- type, pid, options,
- infop, stat_addr, ru);
+ int ret = wait_consider_task(wo, tsk, 0, p);
if (ret)
return ret;
}
@@ -1544,17 +1547,12 @@ static int do_wait_thread(struct task_st
return 0;
}

-static int ptrace_do_wait(struct task_struct *tsk, int *notask_error,
- enum pid_type type, struct pid *pid, int options,
- struct siginfo __user *infop, int __user *stat_addr,
- struct rusage __user *ru)
+static int ptrace_do_wait(struct wait_opts *wo, struct task_struct *tsk)
{
struct task_struct *p;

list_for_each_entry(p, &tsk->ptraced, ptrace_entry) {
- int ret = wait_consider_task(tsk, 1, p, notask_error,
- type, pid, options,
- infop, stat_addr, ru);
+ int ret = wait_consider_task(wo, tsk, 1, p);
if (ret)
return ret;
}
@@ -1562,38 +1560,36 @@ static int ptrace_do_wait(struct task_st
return 0;
}

-static long do_wait(enum pid_type type, struct pid *pid, int options,
- struct siginfo __user *infop, int __user *stat_addr,
- struct rusage __user *ru)
+static long do_wait(struct wait_opts *wo)
{
DECLARE_WAITQUEUE(wait, current);
struct task_struct *tsk;
int retval;

- trace_sched_process_wait(pid);
+ trace_sched_process_wait(wo->wo_pid);

add_wait_queue(&current->signal->wait_chldexit,&wait);
repeat:
/*
* If there is nothing that can match our critiera just get out.
- * We will clear @retval to zero if we see any child that might later
- * match our criteria, even if we are not able to reap it yet.
+ * We will clear ->notask_error to zero if we see any child that
+ * might later match our criteria, even if we are not able to reap
+ * it yet.
*/
- retval = -ECHILD;
- if ((type < PIDTYPE_MAX) && (!pid || hlist_empty(&pid->tasks[type])))
+ retval = wo->notask_error = -ECHILD;
+ if ((wo->wo_type < PIDTYPE_MAX) &&
+ (!wo->wo_pid || hlist_empty(&wo->wo_pid->tasks[wo->wo_type])))
goto end;

current->state = TASK_INTERRUPTIBLE;
read_lock(&tasklist_lock);
tsk = current;
do {
- int tsk_result = do_wait_thread(tsk, &retval,
- type, pid, options,
- infop, stat_addr, ru);
+ int tsk_result = do_wait_thread(wo, tsk);
+
if (!tsk_result)
- tsk_result = ptrace_do_wait(tsk, &retval,
- type, pid, options,
- infop, stat_addr, ru);
+ tsk_result = ptrace_do_wait(wo, tsk);
+
if (tsk_result) {
/*
* tasklist_lock is unlocked and we have a final result.
@@ -1602,25 +1598,27 @@ repeat:
goto end;
}

- if (options & __WNOTHREAD)
+ if (wo->wo_flags & __WNOTHREAD)
break;
tsk = next_thread(tsk);
BUG_ON(tsk->signal != current->signal);
} while (tsk != current);
read_unlock(&tasklist_lock);

- if (!retval && !(options & WNOHANG)) {
+ retval = wo->notask_error;
+ if (!retval && !(wo->wo_flags & WNOHANG)) {
retval = -ERESTARTSYS;
if (!signal_pending(current)) {
schedule();
goto repeat;
}
}
-
end:
current->state = TASK_RUNNING;
remove_wait_queue(&current->signal->wait_chldexit,&wait);
- if (infop) {
+ if (wo->wo_info) {
+ struct siginfo __user *infop = wo->wo_info;
+
if (retval > 0)
retval = 0;
else {
@@ -1649,6 +1647,7 @@ end:
SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
infop, int, options, struct rusage __user *, ru)
{
+ struct wait_opts wo;
struct pid *pid = NULL;
enum pid_type type;
long ret;
@@ -1678,7 +1677,14 @@ SYSCALL_DEFINE5(waitid, int, which, pid_

if (type < PIDTYPE_MAX)
pid = find_get_pid(upid);
- ret = do_wait(type, pid, options, infop, NULL, ru);
+
+ wo.wo_type = type;
+ wo.wo_pid = pid;
+ wo.wo_flags = options;
+ wo.wo_info = infop;
+ wo.wo_stat = NULL;
+ wo.wo_rusage = ru;
+ ret = do_wait(&wo);
put_pid(pid);

/* avoid REGPARM breakage on x86: */
@@ -1689,6 +1695,7 @@ SYSCALL_DEFINE5(waitid, int, which, pid_
SYSCALL_DEFINE4(wait4, pid_t, upid, int __user *, stat_addr,
int, options, struct rusage __user *, ru)
{
+ struct wait_opts wo;
struct pid *pid = NULL;
enum pid_type type;
long ret;
@@ -1710,7 +1717,13 @@ SYSCALL_DEFINE4(wait4, pid_t, upid, int
pid = find_get_pid(upid);
}

- ret = do_wait(type, pid, options | WEXITED, NULL, stat_addr, ru);
+ wo.wo_type = type;
+ wo.wo_pid = pid;
+ wo.wo_flags = options | WEXITED;
+ wo.wo_info = NULL;
+ wo.wo_stat = stat_addr;
+ wo.wo_rusage = ru;
+ ret = do_wait(&wo);
put_pid(pid);

/* avoid REGPARM breakage on x86: */