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Message-ID: <20250920005931.2753828-40-tj@kernel.org>
Date: Fri, 19 Sep 2025 14:59:02 -1000
From: Tejun Heo <tj@...nel.org>
To: void@...ifault.com,
arighi@...dia.com,
multics69@...il.com
Cc: linux-kernel@...r.kernel.org,
sched-ext@...ts.linux.dev,
memxor@...il.com,
bpf@...r.kernel.org,
Tejun Heo <tj@...nel.org>
Subject: [PATCH 39/46] sched_ext: Support dumping multiple schedulers and add scheduler identification
Extend scx_dump_state() to support multiple schedulers and improve task
identification in dumps. The function now takes a specific scheduler to
dump and can optionally filter tasks by scheduler.
scx_dump_task() now displays which scheduler each task belongs to, using
"*" to mark tasks owned by the scheduler being dumped. Sub-schedulers
are identified with their level and cgroup ID.
The SysRq-D handler now iterates through all active schedulers under
scx_sched_lock and dumps each one separately. For SysRq-D dumps, only
tasks owned by each scheduler are dumped to avoid redundancy since all
schedulers are being dumped. Error-triggered dumps continue to dump all
tasks since only that specific scheduler is being dumped.
Signed-off-by: Tejun Heo <tj@...nel.org>
---
kernel/sched/ext.c | 54 ++++++++++++++++++++++++++++++++++++----------
1 file changed, 43 insertions(+), 11 deletions(-)
diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index fafffe3ee812..1a48510e6f98 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -4520,22 +4520,34 @@ static void ops_dump_exit(void)
scx_dump_data.cpu = -1;
}
-static void scx_dump_task(struct seq_buf *s, struct scx_dump_ctx *dctx,
+static void scx_dump_task(struct scx_sched *sch,
+ struct seq_buf *s, struct scx_dump_ctx *dctx,
struct task_struct *p, char marker)
{
static unsigned long bt[SCX_EXIT_BT_LEN];
- struct scx_sched *sch = scx_root;
+ struct scx_sched *task_sch = scx_task_sched(p);
+ const char *own_marker;
+ char sch_id_buf[32];
char dsq_id_buf[19] = "(n/a)";
unsigned long ops_state = atomic_long_read(&p->scx.ops_state);
unsigned int bt_len = 0;
+ own_marker = task_sch == sch ? "*" : "";
+
+ if (task_sch->level == 0)
+ scnprintf(sch_id_buf, sizeof(sch_id_buf), "root");
+ else
+ scnprintf(sch_id_buf, sizeof(sch_id_buf), "sub%d-%llu",
+ task_sch->level, task_sch->ops.sub_cgroup_id);
+
if (p->scx.dsq)
scnprintf(dsq_id_buf, sizeof(dsq_id_buf), "0x%llx",
(unsigned long long)p->scx.dsq->id);
dump_newline(s);
- dump_line(s, " %c%c %s[%d] %+ldms",
+ dump_line(s, " %c%c %s[%d] %s%s %+ldms",
marker, task_state_to_char(p), p->comm, p->pid,
+ own_marker, sch_id_buf,
jiffies_delta_msecs(p->scx.runnable_at, dctx->at_jiffies));
dump_line(s, " scx_state/flags=%u/0x%x dsq_flags=0x%x ops_state/qseq=%lu/%lu",
scx_get_task_state(p), p->scx.flags & ~SCX_TASK_STATE_MASK,
@@ -4563,11 +4575,18 @@ static void scx_dump_task(struct seq_buf *s, struct scx_dump_ctx *dctx,
}
}
-static void scx_dump_state(struct scx_exit_info *ei, size_t dump_len)
+/*
+ * Dump scheduler state. If @dump_all_tasks is true, dump all tasks regardless
+ * of which scheduler they belong to. If false, only dump tasks owned by @sch.
+ * For SysRq-D dumps, @dump_all_tasks=false since all schedulers are dumped
+ * separately. For error dumps, @dump_all_tasks=true since only the failing
+ * scheduler is dumped.
+ */
+static void scx_dump_state(struct scx_sched *sch, struct scx_exit_info *ei,
+ size_t dump_len, bool dump_all_tasks)
{
static DEFINE_RAW_SPINLOCK(dump_lock);
static const char trunc_marker[] = "\n\n~~~~ TRUNCATED ~~~~\n";
- struct scx_sched *sch = scx_root;
struct scx_dump_ctx dctx = {
.kind = ei->kind,
.exit_code = ei->exit_code,
@@ -4584,6 +4603,14 @@ static void scx_dump_state(struct scx_exit_info *ei, size_t dump_len)
seq_buf_init(&s, ei->dump, dump_len);
+#ifdef CONFIG_EXT_SUB_SCHED
+ if (sch->level == 0)
+ dump_line(&s, "%s: root", sch->ops.name);
+ else
+ dump_line(&s, "%s: sub%d-%llu %s",
+ sch->ops.name, sch->level, sch->ops.sub_cgroup_id,
+ sch->cgrp_path);
+#endif
if (ei->kind == SCX_EXIT_NONE) {
dump_line(&s, "Debug dump triggered by %s", ei->reason);
} else {
@@ -4676,11 +4703,13 @@ static void scx_dump_state(struct scx_exit_info *ei, size_t dump_len)
seq_buf_set_overflow(&s);
}
- if (rq->curr->sched_class == &ext_sched_class)
- scx_dump_task(&s, &dctx, rq->curr, '*');
+ if (rq->curr->sched_class == &ext_sched_class &&
+ (dump_all_tasks || scx_task_sched(rq->curr) == sch))
+ scx_dump_task(sch, &s, &dctx, rq->curr, '*');
list_for_each_entry(p, &rq->scx.runnable_list, scx.runnable_node)
- scx_dump_task(&s, &dctx, p, ' ');
+ if (dump_all_tasks || scx_task_sched(p) == sch)
+ scx_dump_task(sch, &s, &dctx, p, ' ');
next:
rq_unlock(rq, &rf);
}
@@ -4712,7 +4741,7 @@ static void scx_error_irq_workfn(struct irq_work *irq_work)
struct scx_exit_info *ei = sch->exit_info;
if (ei->kind >= SCX_EXIT_ERROR)
- scx_dump_state(ei, sch->ops.exit_dump_len);
+ scx_dump_state(sch, ei, sch->ops.exit_dump_len, true);
kthread_queue_work(sch->helper, &sch->disable_work);
}
@@ -5662,9 +5691,12 @@ static const struct sysrq_key_op sysrq_sched_ext_reset_op = {
static void sysrq_handle_sched_ext_dump(u8 key)
{
struct scx_exit_info ei = { .kind = SCX_EXIT_NONE, .reason = "SysRq-D" };
+ struct scx_sched *sch;
- if (scx_enabled())
- scx_dump_state(&ei, 0);
+ guard(raw_spinlock_irqsave)(&scx_sched_lock);
+
+ list_for_each_entry_rcu(sch, &scx_sched_all, all)
+ scx_dump_state(sch, &ei, 0, false);
}
static const struct sysrq_key_op sysrq_sched_ext_dump_op = {
--
2.51.0
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