Evolution-X-Devices/kernel_xiaomi_mt6781
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

tasks: Add a count of task RCU users

Browse Source 
Add a count of the number of RCU users (currently 1) of the task
struct so that we can later add the scheduler case and get rid of the
very subtle task_rcu_dereference(), and just use rcu_dereference().

As suggested by Oleg have the count overlap rcu_head so that no
additional space in task_struct is required.

Change-Id: Ib1f00439f5e119cce4af2bf712df5a60b47fa81f
Inspired-by: Linus Torvalds <torvalds@linux-foundation.org>
Inspired-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Kirill Tkhai <tkhai@yandex.ru>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Russell King - ARM Linux admin <linux@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/87woebdplt.fsf_-_@x220.int.ebiederm.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Git-commit: 3fbd7ee285b2bbc6eebd15a3c8786d9776a402a8
Git-repo: https://android.googlesource.com/kernel/common/
[quic_spathi@quicinc.com: resolved trivial merge conflicts]
Signed-off-by: Srinivasarao Pathipati <quic_spathi@quicinc.com>
This commit is contained in:
Eric W. Biederman
2019-09-14 07:33:34 -05:00
committed by nisel
parent 2f8fb224f3
commit af0b4b4a83
4 changed files with 14 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

5
include/linux/sched.h
View File

@@ -1186,7 +1186,10 @@ struct task_struct {
struct tlbflush_unmap_batch tlb_ubc;
struct rcu_head rcu;
union {
refcount_t rcu_users;
struct rcu_head rcu;
};
/* Cache last used pipe for splice(): */
struct pipe_inode_info *splice_pipe;

1
include/linux/sched/task.h
View File

@@ -107,6 +107,7 @@ static inline void put_task_struct(struct task_struct *t)
}
struct task_struct *task_rcu_dereference(struct task_struct **ptask);
void put_task_struct_rcu_user(struct task_struct *task);
#ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
extern int arch_task_struct_size __read_mostly;

7
kernel/exit.c
View File

@@ -229,6 +229,11 @@ static void delayed_put_task_struct(struct rcu_head *rhp)
put_task_struct(tsk);
}
void put_task_struct_rcu_user(struct task_struct *task)
{
if (refcount_dec_and_test(&task->rcu_users))
call_rcu(&task->rcu, delayed_put_task_struct);
}
void release_task(struct task_struct *p)
{
@@ -269,7 +274,7 @@ repeat:
write_unlock_irq(&tasklist_lock);
release_thread(p);
call_rcu(&p->rcu, delayed_put_task_struct);
put_task_struct_rcu_user(p);
p = leader;
if (unlikely(zap_leader))

7
kernel/fork.c
View File

@@ -871,10 +871,9 @@ static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
tsk->stack_canary = get_random_canary();
#endif
/*
* One for us, one for whoever does the "release_task()" (usually
* parent)
*/
/* One for the user space visible state that goes away when reaped. */
refcount_set(&tsk->rcu_users, 1);
/* One for the rcu users, and one for the scheduler */
atomic_set(&tsk->usage, 2);
#ifdef CONFIG_BLK_DEV_IO_TRACE
tsk->btrace_seq = 0;