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During i915_request_retire() we decouple the i915_request.hwsp_seqno from the intel_timeline so that it may be freed before the request is released. However, we need to warn the compiler that the pointer may update under its nose. [ 171.438899] BUG: KCSAN: data-race in i915_request_await_dma_fence [i915] / i915_request_retire [i915] [ 171.438920] [ 171.438932] write to 0xffff8881e7e28ce0 of 8 bytes by task 148 on cpu 2: [ 171.439174] i915_request_retire+0x1ea/0x660 [i915] [ 171.439408] retire_requests+0x7a/0xd0 [i915] [ 171.439640] engine_retire+0xa1/0xe0 [i915] [ 171.439657] process_one_work+0x3b1/0x690 [ 171.439671] worker_thread+0x80/0x670 [ 171.439685] kthread+0x19a/0x1e0 [ 171.439701] ret_from_fork+0x1f/0x30 [ 171.439721] [ 171.439739] read to 0xffff8881e7e28ce0 of 8 bytes by task 696 on cpu 1: [ 171.439990] i915_request_await_dma_fence+0x162/0x520 [i915] [ 171.440230] i915_request_await_object+0x2fe/0x470 [i915] [ 171.440467] i915_gem_do_execbuffer+0x45dc/0x4c20 [i915] [ 171.440704] i915_gem_execbuffer2_ioctl+0x2c3/0x580 [i915] [ 171.440722] drm_ioctl_kernel+0xe4/0x120 [ 171.440736] drm_ioctl+0x297/0x4c7 [ 171.440750] ksys_ioctl+0x89/0xb0 [ 171.440766] __x64_sys_ioctl+0x42/0x60 [ 171.440788] do_syscall_64+0x6e/0x2c0 [ 171.440802] entry_SYSCALL_64_after_hwframe+0x44/0xa9 Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com> Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20200309110934.868-1-chris@chris-wilson.co.uk
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
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.