Re: [PATCH RFC] m68k: skip kernel premption if interrupts were disabled

[Michael Schmitz <schmitzmic@gmail.com>]

Hi Geert,

On 27/03/24 21:38, Finn Thain wrote:
> On Wed, 27 Mar 2024, Finn Thain wrote:
>
>> On Wed, 27 Mar 2024, Michael Schmitz wrote:
>>
>>> it might be easier for Geert to merge the two patches (or a single one)
>>> on top of his preempt branch if they come in the usual git format.
>> I suppose that would be easier, assuming it doesn't need a lot of rework.
>> Anyway, here's the diff.
>>
>> diff --git a/arch/m68k/mm/motorola.c b/arch/m68k/mm/motorola.c
>> index c1761d309fc6..d0092a3127c0 100644
>> --- a/arch/m68k/mm/motorola.c
>> +++ b/arch/m68k/mm/motorola.c
>> @@ -15,6 +15,7 @@
>>   #include <linux/mm.h>
>>   #include <linux/swap.h>
>>   #include <linux/kernel.h>
>> +#include <linux/preempt.h>
>>   #include <linux/string.h>
>>   #include <linux/types.h>
>>   #include <linux/init.h>
>> @@ -139,10 +140,14 @@ void __init init_pointer_table(void *table, int type)
>>   
>>   void *get_pointer_table(int type)
>>   {
>> -	ptable_desc *dp = ptable_list[type].next;
>> -	unsigned int mask = list_empty(&ptable_list[type]) ? 0 : PD_MARKBITS(dp);
>> +	ptable_desc *dp;
>> +	unsigned int mask;
>>   	unsigned int tmp, off;
>>   
>> +	preempt_disable();
>> +
>> +	dp = ptable_list[type].next;
>> +	mask = list_empty(&ptable_list[type]) ? 0 : PD_MARKBITS(dp);
>>   	/*
>>   	 * For a pointer table for a user process address space, a
>>   	 * table is taken from a page allocated for the purpose.  Each
>> @@ -153,9 +158,13 @@ void *get_pointer_table(int type)
>>   		void *page;
>>   		ptable_desc *new;
>>   
>> +		sched_preempt_enable_no_resched();
>> +
>>   		if (!(page = (void *)get_zeroed_page(GFP_KERNEL)))
>>   			return NULL;
>>   
>> +		preempt_disable();
>> +
>>   		if (type == TABLE_PTE) {
>>   			/*
>>   			 * m68k doesn't have SPLIT_PTE_PTLOCKS for not having
>> @@ -170,6 +179,7 @@ void *get_pointer_table(int type)
>>   		PD_MARKBITS(new) = ptable_mask(type) - 1;
>>   		list_add_tail(new, dp);
>>   
>> +		sched_preempt_enable_no_resched();
>>   		return (pmd_t *)page;
>>   	}
>>   
>> @@ -180,6 +190,7 @@ void *get_pointer_table(int type)
>>   		/* move to end of list */
>>   		list_move_tail(dp, &ptable_list[type]);
>>   	}
>> +	sched_preempt_enable_no_resched();
>>   	return page_address(PD_PAGE(dp)) + off;
>>   }
>>   
>> @@ -190,6 +201,8 @@ int free_pointer_table(void *table, int type)
>>   	unsigned long page = ptable & PAGE_MASK;
>>   	unsigned int mask = 1U << ((ptable - page)/ptable_size(type));
>>   
>> +	preempt_disable();
>> +
>>   	dp = PD_PTABLE(page);
>>   	if (PD_MARKBITS (dp) & mask)
>>   		panic ("table already free!");
>> @@ -203,6 +216,7 @@ int free_pointer_table(void *table, int type)
>>   		if (type == TABLE_PTE)
>>   			pagetable_pte_dtor(virt_to_ptdesc((void *)page));
>>   		free_page (page);
>> +		sched_preempt_enable_no_resched();
>>   		return 1;
>>   	} else if (ptable_list[type].next != dp) {
>>   		/*
>> @@ -211,6 +225,7 @@ int free_pointer_table(void *table, int type)
>>   		 */
>>   		list_move(dp, &ptable_list[type]);
>>   	}
>> +	sched_preempt_enable_no_resched();
>>   	return 0;
>>   }
>>   
>>
> For my part,
>
> Signed-off-by: Finn Thain <fthain@linux-m68k.org>

Same for me:

Signed-off-by: Michael Schmitz <schmitzmic@gmail.com>