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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: Chris Metcalf <cmetcalf@tilera.com>
This commit is contained in:
Chris Metcalf 2012-03-29 15:34:52 -04:00
parent 6731aa9eae
commit 48292738d0
1 changed files with 10 additions and 3 deletions
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13
arch/tile/mm/fault.c
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@ -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. */