[PATCH v9] um: Enable preemption in UML

[Anton Ivanov]

On 01/07/2024 17:35, Johannes Berg wrote:
> On Mon, 2024-07-01 at 17:56 +0200, Johannes Berg wrote:
>> Hmm. I also see a ton of this:
>>
>> BUG: sleeping function called from invalid context at kernel/locking/rwsem.c:1525
>> in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 538, name: chan-switch.sh
>> preempt_count: 2, expected: 0
>> RCU nest depth: 0, expected: 0
>> no locks held by chan-switch.sh/538.
>> irq event stamp: 0
>> hardirqs last  enabled at (0): [<0000000000000000>] 0x0
>> hardirqs last disabled at (0): [<000000006004b961>] copy_process+0xbb7/0x2790
>> softirqs last  enabled at (0): [<000000006004b961>] copy_process+0xbb7/0x2790
>> softirqs last disabled at (0): [<0000000000000000>] 0x0
>> Preemption disabled at:
>> [<0000000060084b04>] preempt_count_add+0x11f/0x126
>> CPU: 0 PID: 538 Comm: chan-switch.sh Tainted: G        W  O       6.10.0-rc2 #11
>> Stack:
>>   714c7e40 605f2a9d 00000000 00000000
>>   ffffff00 607d2edc 00000000 60db7a48
>>   714c7e70 60620823 0000022c 606161d1
>> Call Trace:
>>   [<606161d1>] ? _printk+0x0/0x94
>>   [<6002fa2f>] show_stack+0xfe/0x159
>>   [<605f2a9d>] ? dump_stack_print_info+0xe1/0xf0
>>   [<60620823>] dump_stack_lvl+0x77/0xbe
>>   [<606161d1>] ? _printk+0x0/0x94
>>   [<60084b04>] ? preempt_count_add+0x11f/0x126
>>   [<60620884>] dump_stack+0x1a/0x1c
>>   [<60085b82>] __might_resched+0x3b0/0x3d2
>>   [<60085ca0>] __might_sleep+0xfc/0x107
>>   [<60627212>] down_read+0x34/0x224
>>   [<60032256>] force_flush_all+0x71/0x10d
>
> Which is, however, addressed by my own patchset
>
> https://patchwork.ozlabs.org/project/linux-um/list/?series=374492
>
> though it doesn't apply completely cleanly any more.
>
> johannes
>
As Benjamin pointed out we no longer need this, so we can junk this 
patch at this point. If there will be any need to save/restore FPU in 
kernel context, I will revisit it.

-- 
Anton R. Ivanov
Cambridgegreys Limited. Registered in England. Company Number 10273661
https://www.cambridgegreys.com/