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android, lowmemorykiller: remove task handoff notifier

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The task handoff notifier leaks task_struct since it never gets freed
after the callback returns NOTIFY_OK, which means it is responsible for
doing so.

It turns out the lowmemorykiller actually doesn't need this notifier at
all.  It's used to prevent unnecessary killing by waiting for a thread
to exit as a result of lowmem_shrink(), however, it's possible to do
this in the same way the kernel oom killer works by setting TIF_MEMDIE
and avoid killing if we're still waiting for it to exit.

The kernel oom killer will already automatically set TIF_MEMDIE for
threads that are attempting to allocate memory that have a fatal signal.
The thread selected by lowmem_shrink() will have such a signal after the
lowmemorykiller sends it a SIGKILL, so this won't result in an
unnecessary use of memory reserves for the thread to exit.

This has the added benefit that we don't have to rely on
CONFIG_PROFILING to prevent needlessly killing tasks.

Reported-by: Werner Landgraf <w.landgraf@ru.ru>
Cc: stable@vger.kernel.org
Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: Colin Cross <ccross@android.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
David Rientjes 2012-04-09 16:56:18 -07:00 committed by Linus Torvalds
parent 0034102808
commit 83dbbdbb38
1 changed files with 7 additions and 41 deletions
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48
drivers/staging/android/lowmemorykiller.c
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@ -55,7 +55,6 @@ static int lowmem_minfree[6] = {
};
static int lowmem_minfree_size = 4;
static struct task_struct *lowmem_deathpending;
static unsigned long lowmem_deathpending_timeout;
#define lowmem_print(level, x...) \
@ -64,24 +63,6 @@ static unsigned long lowmem_deathpending_timeout;
printk(x); \
} while (0)
static int
task_notify_func(struct notifier_block *self, unsigned long val, void *data);
static struct notifier_block task_nb = {
.notifier_call = task_notify_func,
};
static int
task_notify_func(struct notifier_block *self, unsigned long val, void *data)
{
struct task_struct *task = data;
if (task == lowmem_deathpending)
lowmem_deathpending = NULL;
return NOTIFY_OK;
}
static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc)
{
struct task_struct *tsk;
@ -97,19 +78,6 @@ static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc)
int other_file = global_page_state(NR_FILE_PAGES) -
global_page_state(NR_SHMEM);
/*
* If we already have a death outstanding, then
* bail out right away; indicating to vmscan
* that we have nothing further to offer on
* this pass.
*
* Note: Currently you need CONFIG_PROFILING
* for this to work correctly.
*/
if (lowmem_deathpending &&
time_before_eq(jiffies, lowmem_deathpending_timeout))
return 0;
if (lowmem_adj_size < array_size)
array_size = lowmem_adj_size;
if (lowmem_minfree_size < array_size)
@ -148,6 +116,12 @@ static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc)
if (!p)
continue;
if (test_tsk_thread_flag(p, TIF_MEMDIE) &&
time_before_eq(jiffies, lowmem_deathpending_timeout)) {
task_unlock(p);
rcu_read_unlock();
return 0;
}
oom_score_adj = p->signal->oom_score_adj;
if (oom_score_adj < min_score_adj) {
task_unlock(p);
@ -174,15 +148,9 @@ static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc)
lowmem_print(1, "send sigkill to %d (%s), adj %d, size %d\n",
selected->pid, selected->comm,
selected_oom_score_adj, selected_tasksize);
/*
* If CONFIG_PROFILING is off, then we don't want to stall
* the killer by setting lowmem_deathpending.
*/
#ifdef CONFIG_PROFILING
lowmem_deathpending = selected;
lowmem_deathpending_timeout = jiffies + HZ;
#endif
send_sig(SIGKILL, selected, 0);
set_tsk_thread_flag(selected, TIF_MEMDIE);
rem -= selected_tasksize;
}
lowmem_print(4, "lowmem_shrink %lu, %x, return %d\n",
@ -198,7 +166,6 @@ static struct shrinker lowmem_shrinker = {
static int __init lowmem_init(void)
{
task_handoff_register(&task_nb);
register_shrinker(&lowmem_shrinker);
return 0;
}
@ -206,7 +173,6 @@ static int __init lowmem_init(void)
static void __exit lowmem_exit(void)
{
unregister_shrinker(&lowmem_shrinker);
task_handoff_unregister(&task_nb);
}
module_param_named(cost, lowmem_shrinker.seeks, int, S_IRUGO | S_IWUSR);