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authorEric W. Biederman <ebiederm@xmission.com>2020-04-25 18:38:54 -0500
committerEric W. Biederman <ebiederm@xmission.com>2020-04-29 07:14:12 -0500
commit9bf7c32409354b4a2fa3207d369a22c8233f718c (patch)
treeb7e785708a6aef7cc000730ee8414cd062de05a5 /kernel/time
parentbbd40fc4816d5329a89397206ece9f1763787a88 (diff)
downloadlinux-9bf7c32409354b4a2fa3207d369a22c8233f718c.tar.bz2
posix-cpu-timers: Extend rcu_read_lock removing task_struct references
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>
Diffstat (limited to 'kernel/time')
-rw-r--r--kernel/time/posix-cpu-timers.c43
1 files 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;
}