Messages in this thread Patch in this message | | | Date | Wed, 11 Apr 2012 16:11:21 -0700 | From | Greg KH <> | Subject | [ 63/78] android, lowmemorykiller: remove task handoff notifier |
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3.3-stable review patch. If anyone has any objections, please let me know.
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From: David Rientjes <rientjes@google.com>
commit 83dbbdbb38666e20a75fad2294cf1df77c52f121 upstream.
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> Signed-off-by: David Rientjes <rientjes@google.com> Acked-by: Colin Cross <ccross@android.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- drivers/staging/android/lowmemorykiller.c | 47 +++--------------------------- 1 file changed, 6 insertions(+), 41 deletions(-)
--- a/drivers/staging/android/lowmemorykiller.c +++ b/drivers/staging/android/lowmemorykiller.c @@ -53,7 +53,6 @@ static size_t 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...) \ @@ -62,24 +61,6 @@ static unsigned long lowmem_deathpending 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 *p; @@ -95,19 +76,6 @@ static int lowmem_shrink(struct shrinker 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) @@ -140,6 +108,11 @@ static int lowmem_shrink(struct shrinker struct signal_struct *sig; int oom_adj; + if (test_tsk_thread_flag(p, TIF_MEMDIE) && + time_before_eq(jiffies, lowmem_deathpending_timeout)) { + read_unlock(&tasklist_lock); + return 0; + } task_lock(p); mm = p->mm; sig = p->signal; @@ -173,15 +146,9 @@ static int lowmem_shrink(struct shrinker lowmem_print(1, "send sigkill to %d (%s), adj %d, size %d\n", selected->pid, selected->comm, selected_oom_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 force_sig(SIGKILL, selected); + set_tsk_thread_flag(selected, TIF_MEMDIE); rem -= selected_tasksize; } lowmem_print(4, "lowmem_shrink %lu, %x, return %d\n", @@ -197,7 +164,6 @@ static struct shrinker lowmem_shrinker = static int __init lowmem_init(void) { - task_handoff_register(&task_nb); register_shrinker(&lowmem_shrinker); return 0; } @@ -205,7 +171,6 @@ 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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