Revert "mm: oom_kill: reap memory of a task that receives SIGKILL"

This reverts commit f9920cf.

Change-Id: I19ec43024ccfb06b27a1f3a63391c423dcbd8f22

Documentation/sysctl/vm.txt

@@ -50,7 +50,6 @@ Currently, these files are in /proc/sys/vm:
 - nr_trim_pages         (only if CONFIG_MMU=n)
 - numa_zonelist_order
 - oom_dump_tasks
-- reap_mem_on_sigkill
 - oom_kill_allocating_task
 - overcommit_kbytes
 - overcommit_memory
@@ -636,24 +635,6 @@ The default value is 1 (enabled).
 
 ==============================================================
 
-reap_mem_on_sigkill
-
-This enables or disables the memory reaping for a SIGKILL received
-process and that the sending process must have the CAP_KILL capabilities.
-
-If this is set to 1, when a process receives SIGKILL from a process
-that has the capability, CAP_KILL, the process is added into the oom_reaper
-queue which can be picked up by the oom_reaper thread to reap the memory of
-that process. This reaps for the process which received SIGKILL through
-either sys_kill from user or kill_pid from kernel.
-
-If this is set to 0, we are not reaping memory of a SIGKILL, sent through
-either sys_kill from user or kill_pid from kernel, received process.
-
-The default value is 0 (disabled).
-
-==============================================================
-
 oom_kill_allocating_task
 
 This enables or disables killing the OOM-triggering task in

include/linux/oom.h

@@ -97,8 +97,4 @@ extern void wake_oom_reaper(struct task_struct *tsk);
 extern int sysctl_oom_dump_tasks;
 extern int sysctl_oom_kill_allocating_task;
 extern int sysctl_panic_on_oom;
-extern int sysctl_reap_mem_on_sigkill;
-
-/* calls for LMK reaper */
-extern void add_to_oom_reaper(struct task_struct *p);
 #endif /* _INCLUDE_LINUX_OOM_H */

kernel/signal.c

@@ -36,8 +36,6 @@
 #include <linux/compat.h>
 #include <linux/cn_proc.h>
 #include <linux/compiler.h>
-#include <linux/oom.h>
-#include <linux/capability.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/signal.h>
@@ -1329,11 +1327,8 @@ int group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
 	ret = check_kill_permission(sig, info, p);
 	rcu_read_unlock();
 
-	if (!ret && sig) {
+	if (!ret && sig)
 		ret = do_send_sig_info(sig, info, p, true);
-		if (capable(CAP_KILL) && sig == SIGKILL)
-			add_to_oom_reaper(p);
-	}
 
 	return ret;
 }

kernel/sysctl.c

@@ -1452,13 +1452,6 @@ static struct ctl_table vm_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec,
 	},
-	{
-		.procname       = "reap_mem_on_sigkill",
-		.data           = &sysctl_reap_mem_on_sigkill,
-		.maxlen         = sizeof(sysctl_reap_mem_on_sigkill),
-		.mode           = 0644,
-		.proc_handler   = proc_dointvec,
-	},
 	{
 		.procname	= "overcommit_ratio",
 		.data		= &sysctl_overcommit_ratio,

mm/oom_kill.c

@@ -49,7 +49,6 @@
 int sysctl_panic_on_oom;
 int sysctl_oom_kill_allocating_task;
 int sysctl_oom_dump_tasks = 1;
-int sysctl_reap_mem_on_sigkill;
 
 DEFINE_MUTEX(oom_lock);
 
@@ -615,10 +614,8 @@ void wake_oom_reaper(struct task_struct *tsk)
 	if (!oom_reaper_th)
 		return;
 
-	/*
-	 * Move the lock here to avoid scenario of queuing
-	 * the same task by both OOM killer and any other SIGKILL
-	 * path.
+	/* move the lock here to avoid scenario of queuing
+	 * the same task by both OOM killer and LMK.
 	 */
 	spin_lock(&oom_reaper_lock);
 
@@ -654,16 +651,6 @@ static inline void wake_oom_reaper(struct task_struct *tsk)
 }
 #endif /* CONFIG_MMU */
 
-static void __mark_oom_victim(struct task_struct *tsk)
-{
-	struct mm_struct *mm = tsk->mm;
-
-	if (!cmpxchg(&tsk->signal->oom_mm, NULL, mm)) {
-		atomic_inc(&tsk->signal->oom_mm->mm_count);
-		set_bit(MMF_OOM_VICTIM, &mm->flags);
-	}
-}
-
 /**
  * mark_oom_victim - mark the given task as OOM victim
  * @tsk: task to mark
@@ -676,13 +663,18 @@ static void __mark_oom_victim(struct task_struct *tsk)
  */
 static void mark_oom_victim(struct task_struct *tsk)
 {
+	struct mm_struct *mm = tsk->mm;
+
 	WARN_ON(oom_killer_disabled);
 	/* OOM killer might race with memcg OOM */
 	if (test_and_set_tsk_thread_flag(tsk, TIF_MEMDIE))
 		return;
 
 	/* oom_mm is bound to the signal struct life time. */
-	__mark_oom_victim(tsk);
+	if (!cmpxchg(&tsk->signal->oom_mm, NULL, mm)) {
+		atomic_inc(&tsk->signal->oom_mm->mm_count);
+		set_bit(MMF_OOM_VICTIM, &mm->flags);
+	}
 
 	/*
 	 * Make sure that the task is woken up from uninterruptible sleep
@@ -1106,22 +1098,3 @@ void pagefault_out_of_memory(void)
 	out_of_memory(&oc);
 	mutex_unlock(&oom_lock);
 }
-
-void add_to_oom_reaper(struct task_struct *p)
-	__releases(p->alloc_lock)
-{
-	if (!sysctl_reap_mem_on_sigkill)
-		return;
-
-	p = find_lock_task_mm(p);
-	if (!p)
-		return;
-
-	get_task_struct(p);
-	if (task_will_free_mem(p)) {
-		__mark_oom_victim(p);
-		wake_oom_reaper(p);
-	}
-	task_unlock(p);
-	put_task_struct(p);
-}