diff --git a/include/linux/sched/ext.h b/include/linux/sched/ext.h
index 65b1740a9a07..6a5a10092fb3 100644
--- a/include/linux/sched/ext.h
+++ b/include/linux/sched/ext.h
@@ -122,6 +122,7 @@ struct sched_ext_entity {
 	atomic_long_t		ops_state;
 
 	struct list_head	runnable_node;	/* rq->scx.runnable_list */
+	unsigned long		runnable_at;
 
 	u64			ddsp_dsq_id;
 	u64			ddsp_enq_flags;
diff --git a/init/init_task.c b/init/init_task.c
index ef349ebe52f8..b85635b7eed0 100644
--- a/init/init_task.c
+++ b/init/init_task.c
@@ -105,6 +105,7 @@ struct task_struct init_task __aligned(L1_CACHE_BYTES) = {
 		.sticky_cpu	= -1,
 		.holding_cpu	= -1,
 		.runnable_node	= LIST_HEAD_INIT(init_task.scx.runnable_node),
+		.runnable_at	= INITIAL_JIFFIES,
 		.ddsp_dsq_id	= SCX_DSQ_INVALID,
 		.slice		= SCX_SLICE_DFL,
 	},
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index ef8fa67c58de..5b921725e6b2 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5733,6 +5733,7 @@ void scheduler_tick(void)
 	calc_global_load_tick(rq);
 	sched_core_tick(rq);
 	task_tick_mm_cid(rq, curr);
+	scx_tick(rq);
 
 	rq_unlock(rq, &rf);
 
diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index e017b79aa1e7..63f47a9e1262 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -8,6 +8,7 @@
 
 enum scx_consts {
 	SCX_DSP_DFL_MAX_BATCH		= 32,
+	SCX_WATCHDOG_MAX_TIMEOUT	= 30 * HZ,
 
 	SCX_EXIT_BT_LEN			= 64,
 	SCX_EXIT_MSG_LEN		= 1024,
@@ -24,6 +25,7 @@ enum scx_exit_kind {
 
 	SCX_EXIT_ERROR = 1024,	/* runtime error, error msg contains details */
 	SCX_EXIT_ERROR_BPF,	/* ERROR but triggered through scx_bpf_error() */
+	SCX_EXIT_ERROR_STALL,	/* watchdog detected stalled runnable tasks */
 };
 
 /*
@@ -319,6 +321,15 @@ struct sched_ext_ops {
 	 */
 	u64 flags;
 
+	/**
+	 * timeout_ms - The maximum amount of time, in milliseconds, that a
+	 * runnable task should be able to wait before being scheduled. The
+	 * maximum timeout may not exceed the default timeout of 30 seconds.
+	 *
+	 * Defaults to the maximum allowed timeout value of 30 seconds.
+	 */
+	u32 timeout_ms;
+
 	/**
 	 * name - BPF scheduler's name
 	 *
@@ -472,6 +483,23 @@ struct static_key_false scx_has_op[SCX_OPI_END] =
 static atomic_t scx_exit_kind = ATOMIC_INIT(SCX_EXIT_DONE);
 static struct scx_exit_info *scx_exit_info;
 
+/*
+ * The maximum amount of time in jiffies that a task may be runnable without
+ * being scheduled on a CPU. If this timeout is exceeded, it will trigger
+ * scx_ops_error().
+ */
+static unsigned long scx_watchdog_timeout;
+
+/*
+ * The last time the delayed work was run. This delayed work relies on
+ * ksoftirqd being able to run to service timer interrupts, so it's possible
+ * that this work itself could get wedged. To account for this, we check that
+ * it's not stalled in the timer tick, and trigger an error if it is.
+ */
+static unsigned long scx_watchdog_timestamp = INITIAL_JIFFIES;
+
+static struct delayed_work scx_watchdog_work;
+
 /* idle tracking */
 #ifdef CONFIG_SMP
 #ifdef CONFIG_CPUMASK_OFFSTACK
@@ -1158,6 +1186,11 @@ static void set_task_runnable(struct rq *rq, struct task_struct *p)
 {
 	lockdep_assert_rq_held(rq);
 
+	if (p->scx.flags & SCX_TASK_RESET_RUNNABLE_AT) {
+		p->scx.runnable_at = jiffies;
+		p->scx.flags &= ~SCX_TASK_RESET_RUNNABLE_AT;
+	}
+
 	/*
 	 * list_add_tail() must be used. scx_ops_bypass() depends on tasks being
 	 * appened to the runnable_list.
@@ -1165,9 +1198,11 @@ static void set_task_runnable(struct rq *rq, struct task_struct *p)
 	list_add_tail(&p->scx.runnable_node, &rq->scx.runnable_list);
 }
 
-static void clr_task_runnable(struct task_struct *p)
+static void clr_task_runnable(struct task_struct *p, bool reset_runnable_at)
 {
 	list_del_init(&p->scx.runnable_node);
+	if (reset_runnable_at)
+		p->scx.flags |= SCX_TASK_RESET_RUNNABLE_AT;
 }
 
 static void enqueue_task_scx(struct rq *rq, struct task_struct *p, int enq_flags)
@@ -1205,7 +1240,8 @@ static void ops_dequeue(struct task_struct *p, u64 deq_flags)
 {
 	unsigned long opss;
 
-	clr_task_runnable(p);
+	/* dequeue is always temporary, don't reset runnable_at */
+	clr_task_runnable(p, false);
 
 	/* acquire ensures that we see the preceding updates on QUEUED */
 	opss = atomic_long_read_acquire(&p->scx.ops_state);
@@ -1818,7 +1854,7 @@ static void set_next_task_scx(struct rq *rq, struct task_struct *p, bool first)
 
 	p->se.exec_start = rq_clock_task(rq);
 
-	clr_task_runnable(p);
+	clr_task_runnable(p, true);
 }
 
 static void put_prev_task_scx(struct rq *rq, struct task_struct *p)
@@ -2168,9 +2204,71 @@ static void reset_idle_masks(void) {}
 
 #endif	/* CONFIG_SMP */
 
-static void task_tick_scx(struct rq *rq, struct task_struct *curr, int queued)
+static bool check_rq_for_timeouts(struct rq *rq)
+{
+	struct task_struct *p;
+	struct rq_flags rf;
+	bool timed_out = false;
+
+	rq_lock_irqsave(rq, &rf);
+	list_for_each_entry(p, &rq->scx.runnable_list, scx.runnable_node) {
+		unsigned long last_runnable = p->scx.runnable_at;
+
+		if (unlikely(time_after(jiffies,
+					last_runnable + scx_watchdog_timeout))) {
+			u32 dur_ms = jiffies_to_msecs(jiffies - last_runnable);
+
+			scx_ops_error_kind(SCX_EXIT_ERROR_STALL,
+					   "%s[%d] failed to run for %u.%03us",
+					   p->comm, p->pid,
+					   dur_ms / 1000, dur_ms % 1000);
+			timed_out = true;
+			break;
+		}
+	}
+	rq_unlock_irqrestore(rq, &rf);
+
+	return timed_out;
+}
+
+static void scx_watchdog_workfn(struct work_struct *work)
+{
+	int cpu;
+
+	WRITE_ONCE(scx_watchdog_timestamp, jiffies);
+
+	for_each_online_cpu(cpu) {
+		if (unlikely(check_rq_for_timeouts(cpu_rq(cpu))))
+			break;
+
+		cond_resched();
+	}
+	queue_delayed_work(system_unbound_wq, to_delayed_work(work),
+			   scx_watchdog_timeout / 2);
+}
+
+void scx_tick(struct rq *rq)
 {
+	unsigned long last_check;
+
+	if (!scx_enabled())
+		return;
+
+	last_check = READ_ONCE(scx_watchdog_timestamp);
+	if (unlikely(time_after(jiffies,
+				last_check + READ_ONCE(scx_watchdog_timeout)))) {
+		u32 dur_ms = jiffies_to_msecs(jiffies - last_check);
+
+		scx_ops_error_kind(SCX_EXIT_ERROR_STALL,
+				   "watchdog failed to check in for %u.%03us",
+				   dur_ms / 1000, dur_ms % 1000);
+	}
+
 	update_other_load_avgs(rq);
+}
+
+static void task_tick_scx(struct rq *rq, struct task_struct *curr, int queued)
+{
 	update_curr_scx(rq);
 
 	/*
@@ -2240,6 +2338,7 @@ static int scx_ops_init_task(struct task_struct *p, struct task_group *tg, bool
 
 	scx_set_task_state(p, SCX_TASK_INIT);
 
+	p->scx.flags |= SCX_TASK_RESET_RUNNABLE_AT;
 	return 0;
 }
 
@@ -2318,6 +2417,7 @@ void init_scx_entity(struct sched_ext_entity *scx)
 	scx->sticky_cpu = -1;
 	scx->holding_cpu = -1;
 	INIT_LIST_HEAD(&scx->runnable_node);
+	scx->runnable_at = jiffies;
 	scx->ddsp_dsq_id = SCX_DSQ_INVALID;
 	scx->slice = SCX_SLICE_DFL;
 }
@@ -2774,6 +2874,8 @@ static const char *scx_exit_reason(enum scx_exit_kind kind)
 		return "runtime error";
 	case SCX_EXIT_ERROR_BPF:
 		return "scx_bpf_error";
+	case SCX_EXIT_ERROR_STALL:
+		return "runnable task stall";
 	default:
 		return "<UNKNOWN>";
 	}
@@ -2883,6 +2985,8 @@ static void scx_ops_disable_workfn(struct kthread_work *work)
 	if (scx_ops.exit)
 		SCX_CALL_OP(SCX_KF_UNLOCKED, exit, ei);
 
+	cancel_delayed_work_sync(&scx_watchdog_work);
+
 	/*
 	 * Delete the kobject from the hierarchy eagerly in addition to just
 	 * dropping a reference. Otherwise, if the object is deleted
@@ -3005,6 +3109,7 @@ static int scx_ops_enable(struct sched_ext_ops *ops)
 {
 	struct scx_task_iter sti;
 	struct task_struct *p;
+	unsigned long timeout;
 	int i, ret;
 
 	mutex_lock(&scx_ops_enable_mutex);
@@ -3081,6 +3186,16 @@ static int scx_ops_enable(struct sched_ext_ops *ops)
 		goto err_disable;
 	}
 
+	if (ops->timeout_ms)
+		timeout = msecs_to_jiffies(ops->timeout_ms);
+	else
+		timeout = SCX_WATCHDOG_MAX_TIMEOUT;
+
+	WRITE_ONCE(scx_watchdog_timeout, timeout);
+	WRITE_ONCE(scx_watchdog_timestamp, jiffies);
+	queue_delayed_work(system_unbound_wq, &scx_watchdog_work,
+			   scx_watchdog_timeout / 2);
+
 	/*
 	 * Lock out forks before opening the floodgate so that they don't wander
 	 * into the operations prematurely.
@@ -3393,6 +3508,12 @@ static int bpf_scx_init_member(const struct btf_type *t,
 		if (ret == 0)
 			return -EINVAL;
 		return 1;
+	case offsetof(struct sched_ext_ops, timeout_ms):
+		if (msecs_to_jiffies(*(u32 *)(udata + moff)) >
+		    SCX_WATCHDOG_MAX_TIMEOUT)
+			return -E2BIG;
+		ops->timeout_ms = *(u32 *)(udata + moff);
+		return 1;
 	}
 
 	return 0;
@@ -3549,6 +3670,7 @@ void __init init_sched_ext_class(void)
 	}
 
 	register_sysrq_key('S', &sysrq_sched_ext_reset_op);
+	INIT_DELAYED_WORK(&scx_watchdog_work, scx_watchdog_workfn);
 }
 
 
diff --git a/kernel/sched/ext.h b/kernel/sched/ext.h
index 328abf5445b1..0a8717b306ba 100644
--- a/kernel/sched/ext.h
+++ b/kernel/sched/ext.h
@@ -29,6 +29,7 @@ static inline bool task_on_scx(const struct task_struct *p)
 	return scx_enabled() && p->sched_class == &ext_sched_class;
 }
 
+void scx_tick(struct rq *rq);
 void init_scx_entity(struct sched_ext_entity *scx);
 void scx_pre_fork(struct task_struct *p);
 int scx_fork(struct task_struct *p);
@@ -75,6 +76,7 @@ static inline const struct sched_class *next_active_class(const struct sched_cla
 #define scx_enabled()		false
 #define scx_switched_all()	false
 
+static inline void scx_tick(struct rq *rq) {}
 static inline void scx_pre_fork(struct task_struct *p) {}
 static inline int scx_fork(struct task_struct *p) { return 0; }
 static inline void scx_post_fork(struct task_struct *p) {}
diff --git a/tools/sched_ext/scx_qmap.bpf.c b/tools/sched_ext/scx_qmap.bpf.c
index ad0328bb3c6a..927c4cd8b218 100644
--- a/tools/sched_ext/scx_qmap.bpf.c
+++ b/tools/sched_ext/scx_qmap.bpf.c
@@ -29,6 +29,8 @@ enum consts {
 char _license[] SEC("license") = "GPL";
 
 const volatile u64 slice_ns = SCX_SLICE_DFL;
+const volatile u32 stall_user_nth;
+const volatile u32 stall_kernel_nth;
 const volatile u32 dsp_batch;
 const volatile bool switch_partial;
 
@@ -130,11 +132,20 @@ static int weight_to_idx(u32 weight)
 
 void BPF_STRUCT_OPS(qmap_enqueue, struct task_struct *p, u64 enq_flags)
 {
+	static u32 user_cnt, kernel_cnt;
 	struct task_ctx *tctx;
 	u32 pid = p->pid;
 	int idx = weight_to_idx(p->scx.weight);
 	void *ring;
 
+	if (p->flags & PF_KTHREAD) {
+		if (stall_kernel_nth && !(++kernel_cnt % stall_kernel_nth))
+			return;
+	} else {
+		if (stall_user_nth && !(++user_cnt % stall_user_nth))
+			return;
+	}
+
 	if (test_error_cnt && !--test_error_cnt)
 		scx_bpf_error("test triggering error");
 
@@ -265,4 +276,5 @@ SCX_OPS_DEFINE(qmap_ops,
 	       .init_task		= (void *)qmap_init_task,
 	       .init			= (void *)qmap_init,
 	       .exit			= (void *)qmap_exit,
+	       .timeout_ms		= 5000U,
 	       .name			= "qmap");
diff --git a/tools/sched_ext/scx_qmap.c b/tools/sched_ext/scx_qmap.c
index 1c0455c64f64..bce3f826cd6f 100644
--- a/tools/sched_ext/scx_qmap.c
+++ b/tools/sched_ext/scx_qmap.c
@@ -19,10 +19,12 @@ const char help_fmt[] =
 "\n"
 "See the top-level comment in .bpf.c for more details.\n"
 "\n"
-"Usage: %s [-s SLICE_US] [-e COUNT] [-b COUNT] [-p] [-v]\n"
+"Usage: %s [-s SLICE_US] [-e COUNT] [-t COUNT] [-T COUNT] [-b COUNT] [-p] [-v]\n"
 "\n"
 "  -s SLICE_US   Override slice duration\n"
 "  -e COUNT      Trigger scx_bpf_error() after COUNT enqueues\n"
+"  -t COUNT      Stall every COUNT'th user thread\n"
+"  -T COUNT      Stall every COUNT'th kernel thread\n"
 "  -b COUNT      Dispatch upto COUNT tasks together\n"
 "  -p            Switch only tasks on SCHED_EXT policy intead of all\n"
 "  -v            Print libbpf debug messages\n"
@@ -55,7 +57,7 @@ int main(int argc, char **argv)
 
 	skel = SCX_OPS_OPEN(qmap_ops, scx_qmap);
 
-	while ((opt = getopt(argc, argv, "s:e:b:pvh")) != -1) {
+	while ((opt = getopt(argc, argv, "s:e:t:T:b:pvh")) != -1) {
 		switch (opt) {
 		case 's':
 			skel->rodata->slice_ns = strtoull(optarg, NULL, 0) * 1000;
@@ -63,6 +65,12 @@ int main(int argc, char **argv)
 		case 'e':
 			skel->bss->test_error_cnt = strtoul(optarg, NULL, 0);
 			break;
+		case 't':
+			skel->rodata->stall_user_nth = strtoul(optarg, NULL, 0);
+			break;
+		case 'T':
+			skel->rodata->stall_kernel_nth = strtoul(optarg, NULL, 0);
+			break;
 		case 'b':
 			skel->rodata->dsp_batch = strtoul(optarg, NULL, 0);
 			break;
