The patch titled
Subject: userfaultfd: fs/userfaultfd.c add more comments
has been removed from the -mm tree. Its filename was
userfaultfd-add-new-syscall-to-provide-memory-externalization-fix-fix.patch
This patch was dropped because it was folded into userfaultfd-add-new-syscall-to-provide-memory-externalization.patch
------------------------------------------------------
From: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Subject: userfaultfd: fs/userfaultfd.c add more comments
Add more commentary.
Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/userfaultfd.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)
diff -puN fs/userfaultfd.c~userfaultfd-add-new-syscall-to-provide-memory-externalization-fix-fix fs/userfaultfd.c
--- a/fs/userfaultfd.c~userfaultfd-add-new-syscall-to-provide-memory-externalization-fix-fix
+++ a/fs/userfaultfd.c
@@ -81,7 +81,20 @@ static int userfaultfd_wake_function(wai
goto out;
ret = wake_up_state(wq->private, mode);
if (ret)
- /* wake only once, autoremove behavior */
+ /*
+ * Wake only once, autoremove behavior.
+ *
+ * After the effect of list_del_init is visible to the
+ * other CPUs, the waitqueue may disappear from under
+ * us, see the !list_empty_careful() in
+ * handle_userfault(). try_to_wake_up() has an
+ * implicit smp_mb__before_spinlock, and the
+ * wq->private is read before calling the extern
+ * function "wake_up_state" (which in turns calls
+ * try_to_wake_up). While the spin_lock;spin_unlock;
+ * wouldn't be enough, the smp_mb__before_spinlock is
+ * enough to avoid an explicit smp_mb() here.
+ */
list_del_init(&wq->task_list);
out:
return ret;
_
Patches currently in -mm which might be from aarcange@xxxxxxxxxx are
userfaultfd-linux-documentation-vm-userfaultfdtxt.patch
userfaultfd-waitqueue-add-nr-wake-parameter-to-__wake_up_locked_key.patch
userfaultfd-uapi.patch
userfaultfd-linux-userfaultfd_kh.patch
userfaultfd-add-vm_userfaultfd_ctx-to-the-vm_area_struct.patch
userfaultfd-add-vm_uffd_missing-and-vm_uffd_wp.patch
userfaultfd-call-handle_userfault-for-userfaultfd_missing-faults.patch
userfaultfd-teach-vma_merge-to-merge-across-vma-vm_userfaultfd_ctx.patch
userfaultfd-prevent-khugepaged-to-merge-if-userfaultfd-is-armed.patch
userfaultfd-add-new-syscall-to-provide-memory-externalization.patch
userfaultfd-add-new-syscall-to-provide-memory-externalization-fix-fix-fix.patch
userfaultfd-rename-uffd_apibits-into-features-fixup.patch
userfaultfd-change-the-read-api-to-return-a-uffd_msg.patch
userfaultfd-change-the-read-api-to-return-a-uffd_msg-fix.patch
userfaultfd-change-the-read-api-to-return-a-uffd_msg-fix-2.patch
userfaultfd-wake-pending-userfaults.patch
userfaultfd-optimize-read-and-poll-to-be-o1.patch
userfaultfd-optimize-read-and-poll-to-be-o1-fix.patch
userfaultfd-allocate-the-userfaultfd_ctx-cacheline-aligned.patch
userfaultfd-solve-the-race-between-uffdio_copyzeropage-and-read.patch
userfaultfd-buildsystem-activation.patch
userfaultfd-activate-syscall.patch
userfaultfd-uffdio_copyuffdio_zeropage-uapi.patch
userfaultfd-mcopy_atomicmfill_zeropage-uffdio_copyuffdio_zeropage-preparation.patch
userfaultfd-avoid-mmap_sem-read-recursion-in-mcopy_atomic.patch
userfaultfd-uffdio_copy-and-uffdio_zeropage.patch
userfaultfd-require-uffdio_api-before-other-ioctls.patch
userfaultfd-allow-signals-to-interrupt-a-userfault.patch
userfaultfd-propagate-the-full-address-in-thp-faults.patch
userfaultfd-avoid-missing-wakeups-during-refile-in-userfaultfd_read.patch
userfaultfd-selftest.patch
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