user/sven/linux.git/kernel/futex.c, branch v5.14.7

Merge tag 'locking-core-2021-06-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2021-06-28T18:45:29Z

Pull locking updates from Ingo Molnar: - Core locking & atomics: - Convert all architectures to ARCH_ATOMIC: move every architecture to ARCH_ATOMIC, then get rid of ARCH_ATOMIC and all the transitory facilities and #ifdefs. Much reduction in complexity from that series: 63 files changed, 756 insertions(+), 4094 deletions(-) - Self-test enhancements - Futexes: - Add the new FUTEX_LOCK_PI2 ABI, which is a variant that doesn't set FLAGS_CLOCKRT (.e. uses CLOCK_MONOTONIC). [ The temptation to repurpose FUTEX_LOCK_PI's implicit setting of FLAGS_CLOCKRT & invert the flag's meaning to avoid having to introduce a new variant was resisted successfully. ] - Enhance futex self-tests - Lockdep: - Fix dependency path printouts - Optimize trace saving - Broaden & fix wait-context checks - Misc cleanups and fixes. * tag 'locking-core-2021-06-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (52 commits) locking/lockdep: Correct the description error for check_redundant() futex: Provide FUTEX_LOCK_PI2 to support clock selection futex: Prepare futex_lock_pi() for runtime clock selection lockdep/selftest: Remove wait-type RCU_CALLBACK tests lockdep/selftests: Fix selftests vs PROVE_RAW_LOCK_NESTING lockdep: Fix wait-type for empty stack locking/selftests: Add a selftest for check_irq_usage() lockding/lockdep: Avoid to find wrong lock dep path in check_irq_usage() locking/lockdep: Remove the unnecessary trace saving locking/lockdep: Fix the dep path printing for backwards BFS selftests: futex: Add futex compare requeue test selftests: futex: Add futex wait test seqlock: Remove trailing semicolon in macros locking/lockdep: Reduce LOCKDEP dependency list locking/lockdep,doc: Improve readability of the block matrix locking/atomics: atomic-instrumented: simplify ifdeffery locking/atomic: delete !ARCH_ATOMIC remnants locking/atomic: xtensa: move to ARCH_ATOMIC locking/atomic: sparc: move to ARCH_ATOMIC locking/atomic: sh: move to ARCH_ATOMIC ...

mm, futex: fix shared futex pgoff on shmem huge page

2021-06-25T02:40:54Z

If more than one futex is placed on a shmem huge page, it can happen that waking the second wakes the first instead, and leaves the second waiting: the key's shared.pgoff is wrong. When 3.11 commit 13d60f4b6ab5 ("futex: Take hugepages into account when generating futex_key"), the only shared huge pages came from hugetlbfs, and the code added to deal with its exceptional page->index was put into hugetlb source. Then that was missed when 4.8 added shmem huge pages. page_to_pgoff() is what others use for this nowadays: except that, as currently written, it gives the right answer on hugetlbfs head, but nonsense on hugetlbfs tails. Fix that by calling hugetlbfs-specific hugetlb_basepage_index() on PageHuge tails as well as on head. Yes, it's unconventional to declare hugetlb_basepage_index() there in pagemap.h, rather than in hugetlb.h; but I do not expect anything but page_to_pgoff() ever to need it. [akpm@linux-foundation.org: give hugetlb_basepage_index() prototype the correct scope] Link: https://lkml.kernel.org/r/b17d946b-d09-326e-b42a-52884c36df32@google.com Fixes: 800d8c63b2e9 ("shmem: add huge pages support") Reported-by: Neel Natu Signed-off-by: Hugh Dickins Reviewed-by: Matthew Wilcox (Oracle) Acked-by: Thomas Gleixner Cc: "Kirill A. Shutemov" Cc: Zhang Yi Cc: Mel Gorman Cc: Mike Kravetz Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Darren Hart Cc: Davidlohr Bueso Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

futex: Provide FUTEX_LOCK_PI2 to support clock selection

2021-06-22T14:42:09Z

The FUTEX_LOCK_PI futex operand uses a CLOCK_REALTIME based absolute timeout since it was implemented, but it does not require that the FUTEX_CLOCK_REALTIME flag is set, because that was introduced later. In theory as none of the user space implementations can set the FUTEX_CLOCK_REALTIME flag on this operand, it would be possible to creatively abuse it and make the meaning invers, i.e. select CLOCK_REALTIME when not set and CLOCK_MONOTONIC when set. But that's a nasty hackery. Another option would be to have a new FUTEX_CLOCK_MONOTONIC flag only for FUTEX_LOCK_PI, but that's also awkward because it does not allow libraries to handle the timeout clock selection consistently. So provide a new FUTEX_LOCK_PI2 operand which implements the timeout semantics which the other operands use and leave FUTEX_LOCK_PI alone. Reported-by: Kurt Kanzenbach Signed-off-by: Thomas Gleixner Signed-off-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20210422194705.440773992@linutronix.de

futex: Prepare futex_lock_pi() for runtime clock selection

2021-06-22T14:42:08Z

futex_lock_pi() is the only futex operation which cannot select the clock for timeouts (CLOCK_MONOTONIC/CLOCK_REALTIME). That's inconsistent and there is no particular reason why this cannot be supported. This was overlooked when CLOCK_REALTIME_FLAG was introduced and unfortunately not reported when the inconsistency was discovered in glibc. Prepare the function and enforce the CLOCK_REALTIME_FLAG on FUTEX_LOCK_PI so that a new FUTEX_LOCK_PI2 can implement it correctly. Reported-by: Kurt Kanzenbach Signed-off-by: Thomas Gleixner Signed-off-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20210422194705.338657741@linutronix.de

futex: Deduplicate cond_resched() invocation in futex_wake_op()

2021-05-25T15:30:15Z

After pagefaulting in futex_wake_op() both branches do cond_resched() before retry. Deduplicate it as compilers cannot figure it out themself. Signed-off-by: Pavel Begunkov Signed-off-by: Thomas Gleixner Reviewed-by: Davidlohr Bueso Link: https://lore.kernel.org/r/9b2588c1fd33c91fb01c4e348a3b647ab2c8baab.1621258128.git.asml.silence@gmail.com

locking: Fix comment typos

2021-05-12T18:11:17Z

A few snuck through. Signed-off-by: Ingo Molnar

futex: Make syscall entry points less convoluted

2021-05-06T18:19:04Z

The futex and the compat syscall entry points do pretty much the same except for the timespec data types and the corresponding copy from user function. Split out the rest into inline functions and share the functionality. Signed-off-by: Thomas Gleixner Acked-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20210422194705.244476369@linutronix.de

futex: Get rid of the val2 conditional dance

2021-05-06T18:19:04Z

There is no point in checking which FUTEX operand treats the utime pointer as 'val2' argument because that argument to do_futex() is only used by exactly these operands. So just handing it in unconditionally is not making any difference, but removes a lot of pointless gunk. Signed-off-by: Thomas Gleixner Acked-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20210422194705.125957049@linutronix.de

futex: Do not apply time namespace adjustment on FUTEX_LOCK_PI

2021-05-06T18:12:40Z

FUTEX_LOCK_PI does not require to have the FUTEX_CLOCK_REALTIME bit set because it has been using CLOCK_REALTIME based absolute timeouts forever. Due to that, the time namespace adjustment which is applied when FUTEX_CLOCK_REALTIME is not set, will wrongly take place for FUTEX_LOCK_PI and wreckage the timeout. Exclude it from that procedure. Fixes: c2f7d08cccf4 ("futex: Adjust absolute futex timeouts with per time namespace offset") Signed-off-by: Thomas Gleixner Acked-by: Peter Zijlstra (Intel) Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20210422194704.984540159@linutronix.de

Revert 337f13046ff0 ("futex: Allow FUTEX_CLOCK_REALTIME with FUTEX_WAIT op")

2021-05-06T18:12:40Z

The FUTEX_WAIT operand has historically a relative timeout which means that the clock id is irrelevant as relative timeouts on CLOCK_REALTIME are not subject to wall clock changes and therefore are mapped by the kernel to CLOCK_MONOTONIC for simplicity. If a caller would set FUTEX_CLOCK_REALTIME for FUTEX_WAIT the timeout is still treated relative vs. CLOCK_MONOTONIC and then the wait arms that timeout based on CLOCK_REALTIME which is broken and obviously has never been used or even tested. Reject any attempt to use FUTEX_CLOCK_REALTIME with FUTEX_WAIT again. The desired functionality can be achieved with FUTEX_WAIT_BITSET and a FUTEX_BITSET_MATCH_ANY argument. Fixes: 337f13046ff0 ("futex: Allow FUTEX_CLOCK_REALTIME with FUTEX_WAIT op") Signed-off-by: Thomas Gleixner Acked-by: Peter Zijlstra (Intel) Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20210422194704.834797921@linutronix.de