From: ebiederm@xmission.com (Eric W. Biederman)
To: LKML <linux-kernel@vger.kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>
Subject: [PATCH v1 1/3] posix-cpu-timers: Extend rcu_read_lock removing task_struct references
Date: Thu, 30 Apr 2020 06:55:54 -0500 [thread overview]
Message-ID: <87bln9427p.fsf_-_@x220.int.ebiederm.org> (raw)
In-Reply-To: <87h7x142an.fsf_-_@x220.int.ebiederm.org> (Eric W. Biederman's message of "Thu, 30 Apr 2020 06:54:08 -0500")
Now that the code stores of pid references it is no longer necessary
or desirable to take a reference on task_struct in __get_task_for_clock.
Instead extend the scope of rcu_read_lock and remove the reference
counting on struct task_struct entirely.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
kernel/time/posix-cpu-timers.c | 43 ++++++++++++++++++----------------
1 file changed, 23 insertions(+), 20 deletions(-)
diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c
index b7f972fb115e..91996dd089a4 100644
--- a/kernel/time/posix-cpu-timers.c
+++ b/kernel/time/posix-cpu-timers.c
@@ -81,36 +81,36 @@ static struct task_struct *lookup_task(const pid_t pid, bool thread,
}
static struct task_struct *__get_task_for_clock(const clockid_t clock,
- bool getref, bool gettime)
+ bool gettime)
{
const bool thread = !!CPUCLOCK_PERTHREAD(clock);
const pid_t pid = CPUCLOCK_PID(clock);
- struct task_struct *p;
if (CPUCLOCK_WHICH(clock) >= CPUCLOCK_MAX)
return NULL;
- rcu_read_lock();
- p = lookup_task(pid, thread, gettime);
- if (p && getref)
- get_task_struct(p);
- rcu_read_unlock();
- return p;
+ return lookup_task(pid, thread, gettime);
}
static inline struct task_struct *get_task_for_clock(const clockid_t clock)
{
- return __get_task_for_clock(clock, true, false);
+ return __get_task_for_clock(clock, false);
}
static inline struct task_struct *get_task_for_clock_get(const clockid_t clock)
{
- return __get_task_for_clock(clock, true, true);
+ return __get_task_for_clock(clock, true);
}
static inline int validate_clock_permissions(const clockid_t clock)
{
- return __get_task_for_clock(clock, false, false) ? 0 : -EINVAL;
+ int ret;
+
+ rcu_read_lock();
+ ret = __get_task_for_clock(clock, false) ? 0 : -EINVAL;
+ rcu_read_unlock();
+
+ return ret;
}
static inline enum pid_type cpu_timer_pid_type(struct k_itimer *timer)
@@ -368,15 +368,18 @@ static int posix_cpu_clock_get(const clockid_t clock, struct timespec64 *tp)
struct task_struct *tsk;
u64 t;
+ rcu_read_lock();
tsk = get_task_for_clock_get(clock);
- if (!tsk)
+ if (!tsk) {
+ rcu_read_unlock();
return -EINVAL;
+ }
if (CPUCLOCK_PERTHREAD(clock))
t = cpu_clock_sample(clkid, tsk);
else
t = cpu_clock_sample_group(clkid, tsk, false);
- put_task_struct(tsk);
+ rcu_read_unlock();
*tp = ns_to_timespec64(t);
return 0;
@@ -389,19 +392,19 @@ static int posix_cpu_clock_get(const clockid_t clock, struct timespec64 *tp)
*/
static int posix_cpu_timer_create(struct k_itimer *new_timer)
{
- struct task_struct *p = get_task_for_clock(new_timer->it_clock);
+ struct task_struct *p;
- if (!p)
+ rcu_read_lock();
+ p = get_task_for_clock(new_timer->it_clock);
+ if (!p) {
+ rcu_read_unlock();
return -EINVAL;
+ }
new_timer->kclock = &clock_posix_cpu;
timerqueue_init(&new_timer->it.cpu.node);
new_timer->it.cpu.pid = get_task_pid(p, cpu_timer_pid_type(new_timer));
- /*
- * get_task_for_clock() took a reference on @p. Drop it as the timer
- * holds a reference on the pid of @p.
- */
- put_task_struct(p);
+ rcu_read_unlock();
return 0;
}
--
2.25.0
next prev parent reply other threads:[~2020-04-30 11:59 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-19 14:10 [PATCH v12 0/7] proc: modernize proc to support multiple private instances Alexey Gladkov
2020-04-19 14:10 ` [PATCH v12 1/7] proc: rename struct proc_fs_info to proc_fs_opts Alexey Gladkov
2020-04-19 14:10 ` [PATCH v12 2/7] proc: allow to mount many instances of proc in one pid namespace Alexey Gladkov
2020-04-23 11:28 ` [PATCH v13 " Alexey Gladkov
2020-04-23 12:16 ` Eric W. Biederman
2020-04-23 20:01 ` Alexey Gladkov
2020-04-19 14:10 ` [PATCH v12 3/7] proc: instantiate only pids that we can ptrace on 'hidepid=4' mount option Alexey Gladkov
2020-04-19 14:10 ` [PATCH v12 4/7] proc: add option to mount only a pids subset Alexey Gladkov
2020-04-19 14:10 ` [PATCH v12 5/7] docs: proc: add documentation for "hidepid=4" and "subset=pid" options and new mount behavior Alexey Gladkov
2020-04-19 14:10 ` [PATCH v12 6/7] proc: use human-readable values for hidepid Alexey Gladkov
2020-04-19 14:10 ` [PATCH v12 7/7] proc: use named enums for better readability Alexey Gladkov
[not found] ` <87ftcv1nqe.fsf@x220.int.ebiederm.org>
2020-04-23 17:54 ` [PATCH v2 0/2] proc: Calling proc_flush_task exactly once per task Oleg Nesterov
2020-04-23 19:38 ` Eric W. Biederman
2020-04-23 19:39 ` [PATCH v2 1/2] proc: Use PIDTYPE_TGID in next_tgid Eric W. Biederman
2020-04-24 17:29 ` Oleg Nesterov
2020-04-23 19:39 ` [PATCH v2 2/2] proc: Ensure we see the exit of each process tid exactly Eric W. Biederman
2020-04-23 20:28 ` Linus Torvalds
2020-04-24 3:33 ` Eric W. Biederman
2020-04-24 18:02 ` Linus Torvalds
2020-04-24 18:46 ` Linus Torvalds
2020-04-24 19:51 ` Eric W. Biederman
2020-04-24 20:10 ` Linus Torvalds
2020-04-24 17:39 ` Oleg Nesterov
2020-04-24 18:10 ` Eric W. Biederman
2020-04-24 20:50 ` [PATCH] proc: Put thread_pid in release_task not proc_flush_pid Eric W. Biederman
[not found] ` <87mu6ymkea.fsf_-_@x220.int.ebiederm.org>
[not found] ` <87blnemj5t.fsf_-_@x220.int.ebiederm.org>
2020-04-26 17:22 ` [PATCH v3 2/6] posix-cpu-timers: Use PIDTYPE_TGID to simplify the logic in lookup_task Oleg Nesterov
2020-04-27 11:51 ` Eric W. Biederman
2020-04-28 18:03 ` Oleg Nesterov
2020-04-27 10:32 ` Thomas Gleixner
2020-04-27 19:46 ` Eric W. Biederman
[not found] ` <875zdmmj4y.fsf_-_@x220.int.ebiederm.org>
2020-04-26 17:40 ` [PATCH v3 3/6] rculist: Add hlist_swap_before_rcu Linus Torvalds
2020-04-27 14:28 ` Eric W. Biederman
2020-04-27 20:27 ` Linus Torvalds
2020-04-28 12:16 ` [PATCH v4 0/2] proc: Ensure we see the exit of each process tid exactly Eric W. Biederman
2020-04-28 12:18 ` [PATCH v4 1/2] rculist: Add hlists_swap_heads_rcu Eric W. Biederman
2020-04-28 12:19 ` [PATCH v4 2/2] proc: Ensure we see the exit of each process tid exactly once Eric W. Biederman
2020-04-28 16:53 ` [PATCH v4 0/2] proc: Ensure we see the exit of each process tid exactly Linus Torvalds
2020-04-28 17:55 ` Eric W. Biederman
2020-04-28 18:55 ` Eric W. Biederman
2020-04-28 19:36 ` Linus Torvalds
2020-04-28 18:05 ` Oleg Nesterov
2020-04-28 18:54 ` Eric W. Biederman
2020-04-28 21:39 ` [PATCH v1 0/4] signal: Removing has_group_leader_pid Eric W. Biederman
2020-04-28 21:45 ` [PATCH v1 1/4] posix-cpu-timer: Tidy up group_leader logic in lookup_task Eric W. Biederman
2020-04-28 21:48 ` [PATCH 2/4] posix-cpu-timer: Unify the now redundant code " Eric W. Biederman
2020-04-28 21:53 ` [PATCH v1 3/4] exec: Remove BUG_ON(has_group_leader_pid) Eric W. Biederman
2020-04-28 21:56 ` [PATCH v4 4/4] signal: Remove has_group_leader_pid Eric W. Biederman
2020-04-30 11:54 ` [PATCH v1 0/3] posix-cpu-timers: Use pids not tasks in lookup Eric W. Biederman
2020-04-30 11:55 ` Eric W. Biederman [this message]
2020-04-30 11:56 ` [PATCH v1 2/3] posix-cpu-timers: Replace cpu_timer_pid_type with clock_pid_type Eric W. Biederman
2020-04-30 11:56 ` [PATCH v1 3/3] posix-cpu-timers: Replace __get_task_for_clock with pid_for_clock Eric W. Biederman
[not found] ` <87h7x6mj6h.fsf_-_@x220.int.ebiederm.org>
2020-04-27 9:43 ` [PATCH v3 1/6] posix-cpu-timers: Always call __get_task_for_clock holding rcu_read_lock Thomas Gleixner
2020-04-27 11:53 ` Eric W. Biederman
[not found] ` <87r1w8ete7.fsf@x220.int.ebiederm.org>
2020-04-27 20:23 ` [PATCH v3] proc: Ensure we see the exit of each process tid exactly Eric W. Biederman
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