Commit 48292738 authored by Chris Metcalf's avatar Chris Metcalf
Browse files

arch/tile: don't wait for migrating PTEs in an NMI handler 



Doing so raises the possibility of self-deadlock if we are waiting
for a backtrace for an oprofile or perf interrupt while we are
in the middle of migrating our own stack page.

Signed-off-by: default avatarChris Metcalf <cmetcalf@tilera.com>
parent 6731aa9e

arch/tile/mm/fault.c

+10 −3
Original line number Diff line number Diff line
@@ -203,9 +203,14 @@ static pgd_t *get_current_pgd(void) 
 * interrupt or a critical region, and must do as little as possible.

 * Similarly, we can't use atomic ops here, since we may be handling a

 * fault caused by an atomic op access.

 *

 * If we find a migrating PTE while we're in an NMI context, and we're

 * at a PC that has a registered exception handler, we don't wait,

 * since this thread may (e.g.) have been interrupted while migrating

 * its own stack, which would then cause us to self-deadlock.

 */

static int handle_migrating_pte(pgd_t *pgd, int fault_num,

				unsigned long address,

				unsigned long address, unsigned long pc,

				int is_kernel_mode, int write)

{

	pud_t *pud;
@@ -227,6 +232,8 @@ static int handle_migrating_pte(pgd_t *pgd, int fault_num, 
		pte_offset_kernel(pmd, address);

	pteval = *pte;

	if (pte_migrating(pteval)) {

		if (in_nmi() && search_exception_tables(pc))

			return 0;

		wait_for_migration(pte);

		return 1;

	}
@@ -300,7 +307,7 @@ static int handle_page_fault(struct pt_regs *regs, 
	 * rather than trying to patch up the existing PTE.

	 */

	pgd = get_current_pgd();

	if (handle_migrating_pte(pgd, fault_num, address,

	if (handle_migrating_pte(pgd, fault_num, address, regs->pc,

				 is_kernel_mode, write))

		return 1;
@@ -665,7 +672,7 @@ struct intvec_state do_page_fault_ics(struct pt_regs *regs, int fault_num, 
	 */

	if (fault_num == INT_DTLB_ACCESS)

		write = 1;

	if (handle_migrating_pte(pgd, fault_num, address, 1, write))

	if (handle_migrating_pte(pgd, fault_num, address, pc, 1, write))

		return state;



	/* Return zero so that we continue on with normal fault handling. */