From 83dbbdbb38666e20a75fad2294cf1df77c52f121 Mon Sep 17 00:00:00 2001 From: David Rientjes Date: Mon, 9 Apr 2012 16:56:18 -0700 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 Landgraf Cc: stable@vger.kernel.org Signed-off-by: David Rientjes Acked-by: Colin Cross Signed-off-by: Linus Torvalds --- 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 index 052b43e4e505..b91e4bc332a7 100644 --- 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);