linux-kernel - [RFC] MIPS: smp: Sleeping func called from start

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Message-ID: <6szkkqxpsw26zajwysdrwplpjvhl5abpnmxgu2xuj3dkzjnvsf@4daqrz4mf44k>
Date: Fri, 2 Aug 2024 11:45:23 +0300
From: Serge Semin <fancer.lancer@...il.com>
To: Thomas Bogendoerfer <tsbogend@...ha.franken.de>, 
	Jiaxun Yang <jiaxun.yang@...goat.com>, Thomas Gleixner <tglx@...utronix.de>
Cc: Serge Semin <fancer.lancer@...il.com>, 
	Andrew Morton <akpm@...ux-foundation.org>, Arnd Bergmann <arnd@...db.de>, 
	Keguang Zhang <keguang.zhang@...il.com>, Gregory CLEMENT <gregory.clement@...tlin.com>, 
	Théo Lebrun <theo.lebrun@...tlin.com>, Vladimir Kondratiev <vladimir.kondratiev@...ileye.com>, 
	Tawfik Bayouk <tawfik.bayouk@...ileye.com>, Huacai Chen <chenhuacai@...nel.org>, linux-mips@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: [RFC] MIPS: smp: Sleeping func called from start_secondary()

Hi folks,

To debug some another problem I recently enabled the
CONFIG_DEBUG_ATOMIC_SLEEP config for my SoC based on the 2xP5600 cores
with MIPS GIC as IRQ-controller. That caused the next BUG backtrace
started being printed to the system log during the device boot-up:

[    0.118053] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:283
[    0.118062] in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 0, name: swapper/1
[    0.118069] preempt_count: 1, expected: 0
[    0.118074] RCU nest depth: 0, expected: 0
[    0.118078] Preemption disabled at:
[    0.118082] [<80105040>] arch_dup_task_struct+0x20/0x118
[    0.118116] CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Not tainted 6.11.0-rc1-bt1-00312-gca6f9469050c-dirty #2460
[    0.118134] Stack : 816d0000 801b89bc 81870000 00000004 a02d0c08 00000000 84ae7dcc 801b84c0
[    0.118167]         00000000 00000002 00000000 00000000 00000000 00000001 84ae7d70 84aaf200
[    0.118195]         00000000 00000000 81115acc 00000000 00000059 84ae7bec 00000000 00000000
[    0.118222]         00000000 ffffffff ffffffea 00000020 816d0000 00000000 81115acc 00000002
[    0.118250]         00000000 04240021 a02d0c08 00000000 00000000 00000000 30400000 ac24242a
[    0.118277]         ...
[    0.118286] Call Trace:
[    0.118289] [<8010af2c>] show_stack+0x88/0x120
[    0.118309] [<80f09dfc>] dump_stack_lvl+0x78/0xb0
[    0.118323] [<801778d0>] __might_resched+0x190/0x1f0
[    0.118349] [<80f10f80>] mutex_lock+0x20/0x74
[    0.118365] [<801c8590>] irq_create_mapping_affinity+0x48/0x104
[    0.118390] [<801121ec>] r4k_clockevent_init+0x58/0x38c
[    0.118402] [<80116658>] start_secondary+0x34/0x134
[    0.118411] [<80f0b1e4>] smp_bootstrap+0x68/0x98
[    0.118424] 

I managed to investigate the problem a bit and the reason turned out to be
in the irq_create_mapping() method eventually invoked in the framework of the
secondary CPU start-up procedure. The more detailed calls chain is:
start_secondary()
+-> mips_clockevent_init()
    +-> r4k_clockevent_init()
        +-> get_c0_compare_int()
            +-> gic_get_c0_compare_int()
                +-> irq_create_mapping()
                    +-> irq_create_mapping_affinity()
                        +-> mutex_lock()
                            +-> might_sleep()
                                +-> might_resched()
                                    +-> __might_resched()
                                        +-> Print the log above

I currently lack of free time for further investigation in an attempt to
find a reasonable solution. So here is just a report and a short summary
of the problem. Should you have any idea of how to fix the problem I'll be
very glad to test it out on a short notice.

-Serge(y)