On Tue, 26 Mar 2024, Michael Schmitz wrote:
see below (hopefully not whitespace-damaged).
Following your approach, I added mutual exclusion to the other candidate in the same file, namely get_pointer_table(). Together with your patch, that seems to be sufficient to make stress-ng happy. I don't know the real extent of the data race here so I've probably used too much locking in this experiment (?) diff --git a/arch/m68k/mm/motorola.c b/arch/m68k/mm/motorola.c index 068ad7c9bb5c..d1ad55ee1b60 100644 --- a/arch/m68k/mm/motorola.c +++ b/arch/m68k/mm/motorola.c @@ -140,10 +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 @@ -154,8 +158,13 @@ void *get_pointer_table(int type) void *page; ptable_desc *new; - if (!(page = (void *)get_zeroed_page(GFP_KERNEL))) + sched_preempt_enable_no_resched(); + + if (!(page = (void *)get_zeroed_page(GFP_KERNEL))) { return NULL; + } + + preempt_disable(); if (type == TABLE_PTE) { /* @@ -171,6 +180,7 @@ 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; } @@ -181,6 +191,7 @@ 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; }