Patch "LoongArch/smp: Call rcutree_report_cpu_starting() earlier" has been added to the 6.1-stable tree

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This is a note to let you know that I've just added the patch titled

    LoongArch/smp: Call rcutree_report_cpu_starting() earlier

to the 6.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     loongarch-smp-call-rcutree_report_cpu_starting-earlier.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From a2ccf46333d7b2cf9658f0d82ac74097c1542fae Mon Sep 17 00:00:00 2001
From: Huacai Chen <chenhuacai@xxxxxxxxxxx>
Date: Wed, 8 Nov 2023 14:12:15 +0800
Subject: LoongArch/smp: Call rcutree_report_cpu_starting() earlier

From: Huacai Chen <chenhuacai@xxxxxxxxxxx>

commit a2ccf46333d7b2cf9658f0d82ac74097c1542fae upstream.

rcutree_report_cpu_starting() must be called before cpu_probe() to avoid
the following lockdep splat that triggered by calling __alloc_pages() when
CONFIG_PROVE_RCU_LIST=y:

 =============================
 WARNING: suspicious RCU usage
 6.6.0+ #980 Not tainted
 -----------------------------
 kernel/locking/lockdep.c:3761 RCU-list traversed in non-reader section!!
 other info that might help us debug this:
 RCU used illegally from offline CPU!
 rcu_scheduler_active = 1, debug_locks = 1
 1 lock held by swapper/1/0:
  #0: 900000000c82ef98 (&pcp->lock){+.+.}-{2:2}, at: get_page_from_freelist+0x894/0x1790
 CPU: 1 PID: 0 Comm: swapper/1 Not tainted 6.6.0+ #980
 Stack : 0000000000000001 9000000004f79508 9000000004893670 9000000100310000
         90000001003137d0 0000000000000000 90000001003137d8 9000000004f79508
         0000000000000000 0000000000000001 0000000000000000 90000000048a3384
         203a656d616e2065 ca43677b3687e616 90000001002c3480 0000000000000008
         000000000000009d 0000000000000000 0000000000000001 80000000ffffe0b8
         000000000000000d 0000000000000033 0000000007ec0000 13bbf50562dad831
         9000000005140748 0000000000000000 9000000004f79508 0000000000000004
         0000000000000000 9000000005140748 90000001002bad40 0000000000000000
         90000001002ba400 0000000000000000 9000000003573ec8 0000000000000000
         00000000000000b0 0000000000000004 0000000000000000 0000000000070000
         ...
 Call Trace:
 [<9000000003573ec8>] show_stack+0x38/0x150
 [<9000000004893670>] dump_stack_lvl+0x74/0xa8
 [<900000000360d2bc>] lockdep_rcu_suspicious+0x14c/0x190
 [<900000000361235c>] __lock_acquire+0xd0c/0x2740
 [<90000000036146f4>] lock_acquire+0x104/0x2c0
 [<90000000048a955c>] _raw_spin_lock_irqsave+0x5c/0x90
 [<900000000381cd5c>] rmqueue_bulk+0x6c/0x950
 [<900000000381fc0c>] get_page_from_freelist+0xd4c/0x1790
 [<9000000003821c6c>] __alloc_pages+0x1bc/0x3e0
 [<9000000003583b40>] tlb_init+0x150/0x2a0
 [<90000000035742a0>] per_cpu_trap_init+0xf0/0x110
 [<90000000035712fc>] cpu_probe+0x3dc/0x7a0
 [<900000000357ed20>] start_secondary+0x40/0xb0
 [<9000000004897138>] smpboot_entry+0x54/0x58

raw_smp_processor_id() is required in order to avoid calling into lockdep
before RCU has declared the CPU to be watched for readers.

See also commit 29368e093921 ("x86/smpboot: Move rcu_cpu_starting() earlier"),
commit de5d9dae150c ("s390/smp: move rcu_cpu_starting() earlier") and commit
99f070b62322 ("powerpc/smp: Call rcu_cpu_starting() earlier").

Signed-off-by: Huacai Chen <chenhuacai@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 arch/loongarch/kernel/smp.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/arch/loongarch/kernel/smp.c
+++ b/arch/loongarch/kernel/smp.c
@@ -471,8 +471,9 @@ asmlinkage void start_secondary(void)
 	unsigned int cpu;
 
 	sync_counter();
-	cpu = smp_processor_id();
+	cpu = raw_smp_processor_id();
 	set_my_cpu_offset(per_cpu_offset(cpu));
+	rcutree_report_cpu_starting(cpu);
 
 	cpu_probe();
 	constant_clockevent_init();


Patches currently in stable-queue which might be from chenhuacai@xxxxxxxxxxx are

queue-6.1/loongarch-smp-call-rcutree_report_cpu_starting-earlier.patch




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