evie/android_kernel_oneplus_msm8998
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mm: process_reclaim: do not iterate over stale task structs

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swap_fn iterates through the threads of selected tasks after
a rcu_read_unlock which is wrong. But we can't extend the
rcu_read_lock since it will result in severe performance
issues. So better avoid iterating over the threads. Just
lock the group leader and use it further.

Change-Id: I36269b1b6619315f33f6f3b49ec73571a66796f2
Signed-off-by: Vinayak Menon <vinmenon@codeaurora.org>
This commit is contained in:
Vinayak Menon 2015-05-21 17:12:37 +05:30 • committed by Kyle Yan
parent 1ad1a93af4
commit 9ff0477006
1 changed files with 12 additions and 19 deletions
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31
mm/process_reclaim.c
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@ -88,14 +88,17 @@ static int test_task_flag(struct task_struct *p, int flag)
{ {
struct task_struct *t = p; struct task_struct *t = p;
do { rcu_read_lock();
for_each_thread(p, t) {
task_lock(t); task_lock(t);
if (test_tsk_thread_flag(t, flag)) { if (test_tsk_thread_flag(t, flag)) {
task_unlock(t); task_unlock(t);
rcu_read_unlock();
return 1; return 1;
} }
task_unlock(t); task_unlock(t);
} while_each_thread(p, t); }
rcu_read_unlock();
return 0; return 0;
} }
@ -125,10 +128,6 @@ static void swap_fn(struct work_struct *work)
if (tsk->flags & PF_KTHREAD) if (tsk->flags & PF_KTHREAD)
continue; continue;
/* if task no longer has any memory ignore it */
if (test_task_flag(tsk, TIF_MM_RELEASED))
continue;
if (test_task_flag(tsk, TIF_MEMDIE)) if (test_task_flag(tsk, TIF_MEMDIE))
continue; continue;
@ -165,20 +164,20 @@ static void swap_fn(struct work_struct *work)
} }
} }
for (i = 0; i < si; i++) { for (i = 0; i < si; i++)
get_task_struct(selected[i].p);
total_sz += selected[i].tasksize; total_sz += selected[i].tasksize;
}
rcu_read_unlock();
/* Skip reclaim if total size is too less */ /* Skip reclaim if total size is too less */
if (total_sz < SWAP_CLUSTER_MAX) { if (total_sz < SWAP_CLUSTER_MAX) {
for (i = 0; i < si; i++) rcu_read_unlock();
put_task_struct(selected[i].p);
return; return;
} }
for (i = 0; i < si; i++)
get_task_struct(selected[i].p);
rcu_read_unlock();
while (si--) { while (si--) {
nr_to_reclaim = nr_to_reclaim =
(selected[si].tasksize * per_swap_size) / total_sz; (selected[si].tasksize * per_swap_size) / total_sz;
@ -186,12 +185,6 @@ static void swap_fn(struct work_struct *work)
if (!nr_to_reclaim) if (!nr_to_reclaim)
nr_to_reclaim = 1; nr_to_reclaim = 1;
if ((test_task_flag(selected[si].p, TIF_MM_RELEASED))
|| (test_task_flag(selected[si].p, TIF_MEMDIE))) {
put_task_struct(selected[si].p);
continue;
}
rp = reclaim_task_anon(selected[si].p, nr_to_reclaim); rp = reclaim_task_anon(selected[si].p, nr_to_reclaim);
trace_process_reclaim(selected[si].tasksize, trace_process_reclaim(selected[si].tasksize,