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We have a race condition in below scenario, say have 3 continuous stripes, sh1, sh2 and sh3, sh1 is the stripe_head of sh2 and sh3: CPU1 CPU2 CPU3 handle_stripe(sh3) stripe_add_to_batch_list(sh3) -> lock(sh2, sh3) -> lock batch_lock(sh1) -> add sh3 to batch_list of sh1 -> unlock batch_lock(sh1) clear_batch_ready(sh1) -> lock(sh1) and batch_lock(sh1) -> clear STRIPE_BATCH_READY for all stripes in batch_list -> unlock(sh1) and batch_lock(sh1) ->clear_batch_ready(sh3) -->test_and_clear_bit(STRIPE_BATCH_READY, sh3) --->return 0 as sh->batch == NULL -> sh3->batch_head = sh1 -> unlock (sh2, sh3) In CPU1, handle_stripe will continue handle sh3 even it's in batch stripe list of sh1. By moving sh3->batch_head assignment in to batch_lock, we make it impossible to clear STRIPE_BATCH_READY before batch_head is set. Thanks Stephane for helping debug this tricky issue. Reported-and-tested-by: Stephane Thiell <sthiell@stanford.edu> Cc: stable@vger.kernel.org (v4.1+) Signed-off-by: Shaohua Li <shli@fb.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.