tools/sched_ext: Fix scx_show_state per-scheduler state reads

scx_show_state.py still reads scx_aborting and scx_bypass_depth as
global symbols. Those symbols no longer exist after the state was mov

tools/sched_ext: Fix scx_show_state per-scheduler state reads

scx_show_state.py still reads scx_aborting and scx_bypass_depth as
global symbols. Those symbols no longer exist after the state was moved
into struct scx_sched, so the drgn script fails when it reaches either
field.

Read aborting and bypass_depth from scx_root instead. This preserves the
script's current root-scheduler view: with sub-scheduler support, the
reported values are for the root scheduler and sub-schedulers are not
enumerated.

Fixes: 5c8d98a1b4de ("sched_ext: Move bypass state into scx_sched")
Fixes: c1743da43cf5 ("sched_ext: Move aborting flag to per-scheduler field")
Signed-off-by: Zicheng Qu <quzicheng@huawei.com>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

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tools/sched_ext: scx_qmap: Silence task_ctx lookup miss

scx_fork() dispatches ops.init_task to exactly one scheduler - the one
owning the forking task's cgroup. A task forked inside a sub-scheduler'

tools/sched_ext: scx_qmap: Silence task_ctx lookup miss

scx_fork() dispatches ops.init_task to exactly one scheduler - the one
owning the forking task's cgroup. A task forked inside a sub-scheduler's
cgroup is init'd into the sub only; the root scheduler has no task_ctx
entry for it. When that task later appears as @prev in the root's
qmap_dispatch() (or flows through core-sched comparison via task_qdist),
the bpf_task_storage_get() legitimately misses.

qmap treated those misses as fatal via scx_bpf_error("task_ctx lookup
failed") and aborted the scheduler as soon as the first cross-sched
task hit the root. Drop the error in the sites where the miss is
legitimate: lookup_task_ctx() (helper; callers already check for NULL),
qmap_dispatch()'s @prev branch (bookkeeping-only), task_qdist()
(returns 0 which makes the comparison a no-op), and qmap_select_cpu()
(returns prev_cpu as a no-op fallback instead of -ESRCH). The existing
scx_error was a paranoid guard from the pre-sub-sched world where every
task was owned by the one and only scheduler.

v2: qmap_select_cpu() returns prev_cpu on NULL instead of -ESRCH, so
the root scheduler doesn't error on cross-sched tasks that pass
through it (Andrea Righi).

Fixes: 4f8b122848db ("sched_ext: Add basic building blocks for nested sub-scheduler dispatching")
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
Reviewed-by: Zhao Mengmeng <zhaomengmeng@kylinos.cn>

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