[PATCH v9] um: Enable preemption in UML

[Johannes Berg]

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