Tejun Heo wrote:
> If
> the possibility of sysrq getting stuck behind concurrency management
> is an issue, queueing them on an unbound or highpri workqueue should
> be good enough.
Regarding SysRq-f, we could do like below. Though I think that converting
the OOM killer into a dedicated kernel thread would allow more things to do
(e.g. Oleg's memory zapping code, my timeout based next victim selection).
diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
index 5381a72..46b951aa 100644
--- a/drivers/tty/sysrq.c
+++ b/drivers/tty/sysrq.c
@@ -47,6 +47,7 @@
#include <linux/syscalls.h>
#include <linux/of.h>
#include <linux/rcupdate.h>
+#include <linux/kthread.h>
#include <asm/ptrace.h>
#include <asm/irq_regs.h>
@@ -351,27 +352,35 @@ static struct sysrq_key_op sysrq_term_op = {
.enable_mask = SYSRQ_ENABLE_SIGNAL,
};
-static void moom_callback(struct work_struct *ignored)
+static DECLARE_WAIT_QUEUE_HEAD(moom_wait);
+
+static int moom_callback(void *unused)
{
const gfp_t gfp_mask = GFP_KERNEL;
- struct oom_control oc = {
- .zonelist = node_zonelist(first_memory_node, gfp_mask),
- .nodemask = NULL,
- .gfp_mask = gfp_mask,
- .order = -1,
- };
-
- mutex_lock(&oom_lock);
- if (!out_of_memory(&oc))
- pr_info("OOM request ignored because killer is disabled\n");
- mutex_unlock(&oom_lock);
+ DEFINE_WAIT(wait);
+
+ while (1) {
+ struct oom_control oc = {
+ .zonelist = node_zonelist(first_memory_node, gfp_mask),
+ .nodemask = NULL,
+ .gfp_mask = gfp_mask,
+ .order = -1,
+ };
+
+ prepare_to_wait(&moom_wait, &wait, TASK_INTERRUPTIBLE);
+ schedule();
+ finish_wait(&moom_wait, &wait);
+ mutex_lock(&oom_lock);
+ if (!out_of_memory(&oc))
+ pr_info("OOM request ignored because killer is disabled\n");
+ mutex_unlock(&oom_lock);
+ }
+ return 0;
}
-static DECLARE_WORK(moom_work, moom_callback);
-
static void sysrq_handle_moom(int key)
{
- schedule_work(&moom_work);
+ wake_up(&moom_wait);
}
static struct sysrq_key_op sysrq_moom_op = {
.handler = sysrq_handle_moom,
@@ -1116,6 +1125,9 @@ static inline void sysrq_init_procfs(void)
static int __init sysrq_init(void)
{
+ struct task_struct *task = kthread_run(moom_callback, NULL,
+ "manual_oom");
+ BUG_ON(IS_ERR(task));
sysrq_init_procfs();
if (sysrq_on())
--
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