mm: Add ptep_try_set() for lockless empty-slot installs

[kernel-patches-daemon-bpf]

Pull request for series with
subject: mm: Add ptep_try_set() for lockless empty-slot installs
version: 1
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=1099523

[kernel-patches-daemon-bpf]

Upstream branch: 49b1831
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=1099523
version: 1

Pull request is NOT updated. Failed to apply https://patchwork.kernel.org/project/netdevbpf/list/?series=1099523
error message:

Cmd('git') failed due to: exit code(128)
  cmdline: git am --3way
  stdout: 'Applying: mm: Add ptep_try_set() for lockless empty-slot installs
Applying: bpf: Recover arena kernel faults with scratch page
Using index info to reconstruct a base tree...
M	arch/arm64/mm/fault.c
M	arch/x86/mm/fault.c
M	include/linux/bpf.h
M	kernel/bpf/arena.c
M	kernel/bpf/core.c
Falling back to patching base and 3-way merge...
Auto-merging arch/arm64/mm/fault.c
Auto-merging arch/x86/mm/fault.c
Auto-merging include/linux/bpf.h
Auto-merging kernel/bpf/arena.c
Auto-merging kernel/bpf/core.c
Applying: bpf: Add sleepable variant of bpf_arena_alloc_pages for kernel callers
Applying: bpf: Add bpf_struct_ops_for_each_prog()
Applying: bpf/arena: Add bpf_arena_map_kern_vm_start() and bpf_prog_arena()
Applying: sched_ext: Require an arena for cid-form schedulers
Using index info to reconstruct a base tree...
M	kernel/sched/ext.c
M	kernel/sched/ext_internal.h
Falling back to patching base and 3-way merge...
Auto-merging kernel/sched/ext.c
CONFLICT (content): Merge conflict in kernel/sched/ext.c
Auto-merging kernel/sched/ext_internal.h
CONFLICT (content): Merge conflict in kernel/sched/ext_internal.h
Patch failed at 0006 sched_ext: Require an arena for cid-form schedulers'
  stderr: 'error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
hint: When you have resolved this problem, run "git am --continue".
hint: If you prefer to skip this patch, run "git am --skip" instead.
hint: To restore the original branch and stop patching, run "git am --abort".
hint: Disable this message with "git config set advice.mergeConflict false"'

conflict:

diff --cc kernel/sched/ext.c
index 38d90baf78cf,56f94ac32ba0..000000000000
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@@ -6492,6 -6735,24 +6494,27 @@@ static struct scx_sched_pnode *alloc_pn
  }
  
  /*
++<<<<<<< HEAD
++=======
+  * scx_enable() is offloaded to a dedicated system-wide RT kthread to avoid
+  * starvation. During the READY -> ENABLED task switching loop, the calling
+  * thread's sched_class gets switched from fair to ext. As fair has higher
+  * priority than ext, the calling thread can be indefinitely starved under
+  * fair-class saturation, leading to a system hang.
+  */
+ struct scx_enable_cmd {
+ 	struct kthread_work	work;
+ 	union {
+ 		struct sched_ext_ops		*ops;
+ 		struct sched_ext_ops_cid	*ops_cid;
+ 	};
+ 	bool			is_cid_type;
+ 	struct bpf_map		*arena_map;	/* arena ref to transfer to sch */
+ 	int			ret;
+ };
+ 
+ /*
++>>>>>>> sched_ext: Require an arena for cid-form schedulers
   * Allocate and initialize a new scx_sched. @cgrp's reference is always
   * consumed whether the function succeeds or fails.
   */
@@@ -6639,10 -6916,22 +6662,19 @@@ static struct scx_sched *scx_alloc_and_
  		return ERR_PTR(ret);
  	}
  #endif	/* CONFIG_EXT_SUB_SCHED */
+ 
+ 	/*
+ 	 * Consume the arena_map ref bpf_scx_reg_cid() took. Defer to here so
+ 	 * earlier failure paths leave cmd->arena_map set and bpf_scx_reg_cid
+ 	 * drops the ref. After this point, sch owns the ref and any cleanup
+ 	 * runs through scx_sched_free_rcu_work() which puts it.
+ 	 */
+ 	sch->arena_map = cmd->arena_map;
+ 	cmd->arena_map = NULL;
  	return sch;
  
 -#ifdef CONFIG_EXT_SUB_SCHED
  err_free_lb_resched:
 -	RCU_INIT_POINTER(ops->priv, NULL);
  	free_cpumask_var(sch->bypass_lb_resched_cpumask);
 -#endif
  err_free_lb_cpumask:
  	free_cpumask_var(sch->bypass_lb_donee_cpumask);
  err_stop_helper:
@@@ -7504,7 -7905,58 +7536,62 @@@ static int bpf_scx_check_member(const s
  
  static int bpf_scx_reg(void *kdata, struct bpf_link *link)
  {
++<<<<<<< HEAD
 +	return scx_enable(kdata, link);
++=======
+ 	struct scx_enable_cmd cmd = { .ops = kdata };
+ 
+ 	return scx_enable(&cmd, link);
+ }
+ 
+ struct scx_arena_scan {
+ 	struct bpf_map	*arena;
+ 	int		err;
+ };
+ 
+ /*
+  * The verifier enforces one arena per BPF program, so each struct_ops
+  * member prog contributes at most one arena via bpf_prog_arena().
+  * Require all non-NULL contributions to match.
+  */
+ static int scx_arena_scan_prog(struct bpf_prog *prog, void *data)
+ {
+ 	struct scx_arena_scan *s = data;
+ 	struct bpf_map *arena = bpf_prog_arena(prog);
+ 
+ 	if (!arena)
+ 		return 0;
+ 	if (s->arena && s->arena != arena) {
+ 		s->err = -EINVAL;
+ 		return 1;
+ 	}
+ 	s->arena = arena;
+ 	return 0;
+ }
+ 
+ static int bpf_scx_reg_cid(void *kdata, struct bpf_link *link)
+ {
+ 	struct scx_enable_cmd cmd = { .ops_cid = kdata, .is_cid_type = true };
+ 	struct scx_arena_scan scan = {};
+ 	int ret;
+ 
+ 	bpf_struct_ops_for_each_prog(kdata, scx_arena_scan_prog, &scan);
+ 	if (scan.err) {
+ 		pr_err("sched_ext: cid-form scheduler uses multiple arena maps\n");
+ 		return scan.err;
+ 	}
+ 	if (!scan.arena) {
+ 		pr_err("sched_ext: cid-form scheduler must use a BPF arena map\n");
+ 		return -EINVAL;
+ 	}
+ 
+ 	bpf_map_inc(scan.arena);
+ 	cmd.arena_map = scan.arena;
+ 	ret = scx_enable(&cmd, link);
+ 	if (cmd.arena_map)		/* not consumed by scx_alloc_and_add_sched() */
+ 		bpf_map_put(cmd.arena_map);
+ 	return ret;
++>>>>>>> sched_ext: Require an arena for cid-form schedulers
  }
  
  static void bpf_scx_unreg(void *kdata, struct bpf_link *link)
diff --cc kernel/sched/ext_internal.h
index a075732d4430,d40cfd29ddaa..000000000000
--- a/kernel/sched/ext_internal.h
+++ b/kernel/sched/ext_internal.h
@@@ -1009,7 -1099,26 +1009,30 @@@ struct scx_sched_pnode 
  };
  
  struct scx_sched {
++<<<<<<< HEAD
 +	struct sched_ext_ops	ops;
++=======
+ 	/*
+ 	 * cpu-form and cid-form ops share field offsets up to .priv (verified
+ 	 * by BUILD_BUG_ON in scx_init()). The anonymous union lets the kernel
+ 	 * access either view of the same storage without function-pointer
+ 	 * casts: use .ops for cpu-form and shared fields, .ops_cid for the
+ 	 * cid-renamed callbacks (set_cmask, select_cid, cid_online, ...).
+ 	 */
+ 	union {
+ 		struct sched_ext_ops		ops;
+ 		struct sched_ext_ops_cid	ops_cid;
+ 	};
+ 	bool			is_cid_type;	/* true if registered via bpf_sched_ext_ops_cid */
+ 
+ 	/*
+ 	 * Arena map auto-discovered from member progs at struct_ops attach.
+ 	 * cid-form schedulers must use exactly one arena across all member
+ 	 * progs. NULL on cpu-form.
+ 	 */
+ 	struct bpf_map		*arena_map;
+ 
++>>>>>>> sched_ext: Require an arena for cid-form schedulers
  	DECLARE_BITMAP(has_op, SCX_OPI_END);
  
  	/*