diff options
Diffstat (limited to 'arch/powerpc/mm/book3s64/hash_utils.c')
| -rw-r--r-- | arch/powerpc/mm/book3s64/hash_utils.c | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/arch/powerpc/mm/book3s64/hash_utils.c b/arch/powerpc/mm/book3s64/hash_utils.c index 468169e33c86..9b9f92ad0e7a 100644 --- a/arch/powerpc/mm/book3s64/hash_utils.c +++ b/arch/powerpc/mm/book3s64/hash_utils.c @@ -1559,6 +1559,7 @@ static void hash_preload(struct mm_struct *mm, pte_t *ptep, unsigned long ea, pgd_t *pgdir; int rc, ssize, update_flags = 0; unsigned long access = _PAGE_PRESENT | _PAGE_READ | (is_exec ? _PAGE_EXEC : 0); + unsigned long flags; BUG_ON(get_region_id(ea) != USER_REGION_ID); @@ -1592,6 +1593,28 @@ static void hash_preload(struct mm_struct *mm, pte_t *ptep, unsigned long ea, return; #endif /* CONFIG_PPC_64K_PAGES */ + /* + * __hash_page_* must run with interrupts off, as it sets the + * H_PAGE_BUSY bit. It's possible for perf interrupts to hit at any + * time and may take a hash fault reading the user stack, see + * read_user_stack_slow() in the powerpc/perf code. + * + * If that takes a hash fault on the same page as we lock here, it + * will bail out when seeing H_PAGE_BUSY set, and retry the access + * leading to an infinite loop. + * + * Disabling interrupts here does not prevent perf interrupts, but it + * will prevent them taking hash faults (see the NMI test in + * do_hash_page), then read_user_stack's copy_from_user_nofault will + * fail and perf will fall back to read_user_stack_slow(), which + * walks the Linux page tables. + * + * Interrupts must also be off for the duration of the + * mm_is_thread_local test and update, to prevent preempt running the + * mm on another CPU (XXX: this may be racy vs kthread_use_mm). + */ + local_irq_save(flags); + /* Is that local to this CPU ? */ if (mm_is_thread_local(mm)) update_flags |= HPTE_LOCAL_UPDATE; @@ -1614,6 +1637,8 @@ static void hash_preload(struct mm_struct *mm, pte_t *ptep, unsigned long ea, mm_ctx_user_psize(&mm->context), mm_ctx_user_psize(&mm->context), pte_val(*ptep)); + + local_irq_restore(flags); } /* |