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Date: Mon, 9 Apr 2012 16:56:18 -0700 (PDT)
From: David Rientjes <rientjes@...gle.com>
To: Linus Torvalds <torvalds@...ux-foundation.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>
cc: Andrew Morton <akpm@...ux-foundation.org>,
werner <w.landgraf@...ru>, Rik van Riel <riel@...hat.com>,
Hugh Dickins <hughd@...gle.com>, linux-kernel@...r.kernel.org,
Oleg Nesterov <oleg@...hat.com>,
Rabin Vincent <rabin.vincent@...ricsson.com>,
Christian Bejram <christian.bejram@...ricsson.com>,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
Anton Vorontsov <anton.vorontsov@...aro.org>,
stable@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
Colin Cross <ccross@...gle.com>
Subject: [patch] android, lowmemorykiller: remove task handoff notifier
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 <w.landgraf@...ru>
Cc: stable@...r.kernel.org
Signed-off-by: David Rientjes <rientjes@...gle.com>
---
drivers/staging/android/lowmemorykiller.c | 48 +++++------------------------
1 file changed, 7 insertions(+), 41 deletions(-)
diff --git a/drivers/staging/android/lowmemorykiller.c b/drivers/staging/android/lowmemorykiller.c
--- a/drivers/staging/android/lowmemorykiller.c
+++ b/drivers/staging/android/lowmemorykiller.c
@@ -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);
--
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