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Message-ID: <20230612093538.546520916@infradead.org>
Date: Mon, 12 Jun 2023 11:07:28 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: torvalds@...ux-foundation.org, keescook@...omium.org,
gregkh@...uxfoundation.org, pbonzini@...hat.com
Cc: masahiroy@...nel.org, nathan@...nel.org, ndesaulniers@...gle.com,
nicolas@...sle.eu, catalin.marinas@....com, will@...nel.org,
vkoul@...nel.org, trix@...hat.com, ojeda@...nel.org,
peterz@...radead.org, mingo@...hat.com, longman@...hat.com,
boqun.feng@...il.com, dennis@...nel.org, tj@...nel.org,
cl@...ux.com, acme@...nel.org, mark.rutland@....com,
alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
namhyung@...nel.org, irogers@...gle.com, adrian.hunter@...el.com,
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Subject: [PATCH v3 15/57] sched: Simplify syscalls
Use guards to reduce gotos and simplify control flow.
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
kernel/sched/core.c | 154 ++++++++++++++++++++++------------------------------
1 file changed, 68 insertions(+), 86 deletions(-)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7425,6 +7425,21 @@ static struct task_struct *find_process_
return pid ? find_task_by_vpid(pid) : current;
}
+static struct task_struct *find_get_task(pid_t pid)
+{
+ struct task_struct *p;
+ guard(rcu)();
+
+ p = find_process_by_pid(pid);
+ if (likely(p))
+ get_task_struct(p);
+
+ return p;
+}
+
+DEFINE_CLASS(find_get_task, struct task_struct *, if (_T) put_task_struct(_T),
+ find_get_task(pid), pid_t pid)
+
/*
* sched_setparam() passes in -1 for its policy, to let the functions
* it calls know not to change it.
@@ -7462,14 +7477,11 @@ static void __setscheduler_params(struct
static bool check_same_owner(struct task_struct *p)
{
const struct cred *cred = current_cred(), *pcred;
- bool match;
+ guard(rcu)();
- rcu_read_lock();
pcred = __task_cred(p);
- match = (uid_eq(cred->euid, pcred->euid) ||
- uid_eq(cred->euid, pcred->uid));
- rcu_read_unlock();
- return match;
+ return (uid_eq(cred->euid, pcred->euid) ||
+ uid_eq(cred->euid, pcred->uid));
}
/*
@@ -7873,27 +7885,17 @@ static int
do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param)
{
struct sched_param lparam;
- struct task_struct *p;
- int retval;
if (!param || pid < 0)
return -EINVAL;
if (copy_from_user(&lparam, param, sizeof(struct sched_param)))
return -EFAULT;
- rcu_read_lock();
- retval = -ESRCH;
- p = find_process_by_pid(pid);
- if (likely(p))
- get_task_struct(p);
- rcu_read_unlock();
-
- if (likely(p)) {
- retval = sched_setscheduler(p, policy, &lparam);
- put_task_struct(p);
- }
+ CLASS(find_get_task, p)(pid);
+ if (!p)
+ return -ESRCH;
- return retval;
+ return sched_setscheduler(p, policy, &lparam);
}
/*
@@ -7989,7 +7991,6 @@ SYSCALL_DEFINE3(sched_setattr, pid_t, pi
unsigned int, flags)
{
struct sched_attr attr;
- struct task_struct *p;
int retval;
if (!uattr || pid < 0 || flags)
@@ -8004,21 +8005,14 @@ SYSCALL_DEFINE3(sched_setattr, pid_t, pi
if (attr.sched_flags & SCHED_FLAG_KEEP_POLICY)
attr.sched_policy = SETPARAM_POLICY;
- rcu_read_lock();
- retval = -ESRCH;
- p = find_process_by_pid(pid);
- if (likely(p))
- get_task_struct(p);
- rcu_read_unlock();
+ CLASS(find_get_task, p)(pid);
+ if (!p)
+ return -ESRCH;
- if (likely(p)) {
- if (attr.sched_flags & SCHED_FLAG_KEEP_PARAMS)
- get_params(p, &attr);
- retval = sched_setattr(p, &attr);
- put_task_struct(p);
- }
+ if (attr.sched_flags & SCHED_FLAG_KEEP_PARAMS)
+ get_params(p, &attr);
- return retval;
+ return sched_setattr(p, &attr);
}
/**
@@ -8036,16 +8030,17 @@ SYSCALL_DEFINE1(sched_getscheduler, pid_
if (pid < 0)
return -EINVAL;
- retval = -ESRCH;
- rcu_read_lock();
+ guard(rcu)();
p = find_process_by_pid(pid);
- if (p) {
- retval = security_task_getscheduler(p);
- if (!retval)
- retval = p->policy
- | (p->sched_reset_on_fork ? SCHED_RESET_ON_FORK : 0);
+ if (!p)
+ return -ESRCH;
+
+ retval = security_task_getscheduler(p);
+ if (!retval) {
+ retval = p->policy;
+ if (p->sched_reset_on_fork)
+ retval |= SCHED_RESET_ON_FORK;
}
- rcu_read_unlock();
return retval;
}
@@ -8066,30 +8061,23 @@ SYSCALL_DEFINE2(sched_getparam, pid_t, p
if (!param || pid < 0)
return -EINVAL;
- rcu_read_lock();
- p = find_process_by_pid(pid);
- retval = -ESRCH;
- if (!p)
- goto out_unlock;
+ scoped_guard (rcu) {
+ p = find_process_by_pid(pid);
+ if (!p)
+ return -ESRCH;
- retval = security_task_getscheduler(p);
- if (retval)
- goto out_unlock;
+ retval = security_task_getscheduler(p);
+ if (retval)
+ return retval;
- if (task_has_rt_policy(p))
- lp.sched_priority = p->rt_priority;
- rcu_read_unlock();
+ if (task_has_rt_policy(p))
+ lp.sched_priority = p->rt_priority;
+ }
/*
* This one might sleep, we cannot do it with a spinlock held ...
*/
- retval = copy_to_user(param, &lp, sizeof(*param)) ? -EFAULT : 0;
-
- return retval;
-
-out_unlock:
- rcu_read_unlock();
- return retval;
+ return copy_to_user(param, &lp, sizeof(*param)) ? -EFAULT : 0;
}
/*
@@ -8149,39 +8137,33 @@ SYSCALL_DEFINE4(sched_getattr, pid_t, pi
usize < SCHED_ATTR_SIZE_VER0 || flags)
return -EINVAL;
- rcu_read_lock();
- p = find_process_by_pid(pid);
- retval = -ESRCH;
- if (!p)
- goto out_unlock;
+ scoped_guard (rcu) {
+ p = find_process_by_pid(pid);
+ if (!p)
+ return -ESRCH;
- retval = security_task_getscheduler(p);
- if (retval)
- goto out_unlock;
+ retval = security_task_getscheduler(p);
+ if (retval)
+ return retval;
- kattr.sched_policy = p->policy;
- if (p->sched_reset_on_fork)
- kattr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
- get_params(p, &kattr);
- kattr.sched_flags &= SCHED_FLAG_ALL;
+ kattr.sched_policy = p->policy;
+ if (p->sched_reset_on_fork)
+ kattr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
+ get_params(p, &kattr);
+ kattr.sched_flags &= SCHED_FLAG_ALL;
#ifdef CONFIG_UCLAMP_TASK
- /*
- * This could race with another potential updater, but this is fine
- * because it'll correctly read the old or the new value. We don't need
- * to guarantee who wins the race as long as it doesn't return garbage.
- */
- kattr.sched_util_min = p->uclamp_req[UCLAMP_MIN].value;
- kattr.sched_util_max = p->uclamp_req[UCLAMP_MAX].value;
+ /*
+ * This could race with another potential updater, but this is fine
+ * because it'll correctly read the old or the new value. We don't need
+ * to guarantee who wins the race as long as it doesn't return garbage.
+ */
+ kattr.sched_util_min = p->uclamp_req[UCLAMP_MIN].value;
+ kattr.sched_util_max = p->uclamp_req[UCLAMP_MAX].value;
#endif
-
- rcu_read_unlock();
+ }
return sched_attr_copy_to_user(uattr, &kattr, usize);
-
-out_unlock:
- rcu_read_unlock();
- return retval;
}
#ifdef CONFIG_SMP
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