On Fri, 2011-07-15 at 16:07 +0800, Shan Hai wrote: > > The following test case could reveal a bug in the futex_lock_pi() > > BUG: On FUTEX_LOCK_PI, there is a infinite loop in the futex_lock_pi() > on Powerpc e500 core. > Cause: The linux kernel on the e500 core has no write permission on > the COW page, refer the head comment of the following test code. > > ftrace on test case: > [000] 353.990181: futex_lock_pi_atomic <-futex_lock_pi > [000] 353.990185: cmpxchg_futex_value_locked <-futex_lock_pi_atomic > [snip] > [000] 353.990191: do_page_fault <-handle_page_fault > [000] 353.990192: bad_page_fault <-handle_page_fault > [000] 353.990193: search_exception_tables <-bad_page_fault > [snip] > [000] 353.990199: get_user_pages <-fault_in_user_writeable > [snip] > [000] 353.990208: mark_page_accessed <-follow_page > [000] 353.990222: futex_lock_pi_atomic <-futex_lock_pi > [snip] > [000] 353.990230: cmpxchg_futex_value_locked <-futex_lock_pi_atomic > [ a loop occures here ] >
But but but but, that get_user_pages(.write=1, .force=0) should result in a COW break, getting our own writable page. What is this e500 thing smoking that this doesn't work? _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
