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Message-ID: <CAPM=9tyRYFJkPr3DcjfVM4soB-ErTZWXWmXxsFKaSq4MqqjPNQ@mail.gmail.com>
Date: Thu, 28 May 2015 13:38:11 +1000
From: Dave Airlie <airlied@...il.com>
To: Frediano Ziglio <fziglio@...hat.com>
Cc: spice-devel <spice-devel@...ts.freedesktop.org>,
David Airlie <airlied@...ux.ie>,
dri-devel <dri-devel@...ts.freedesktop.org>,
Dave Airlie <airlied@...hat.com>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [Spice-devel] [PATCH] Do not loop on ERESTARTSYS using
interruptible waits
On 19 May 2015 at 19:54, Frediano Ziglio <fziglio@...hat.com> wrote:
> This problem happens using KMS surfaces and QXL driver.
> To easy reproduce use KDE Plasma (which use surfaces a lot) and assure
> you are using KMS surfaces (QXL driver on Fedora/RedHat has a patch to
> stop using them). Open some complex application like LibreOffice and
> after a while your machine get stuck using 100% CPU on Xorg.
> The problem occurs as creating new surfaces not interruptible wait
> are used however instead of returning ERESTARTSYS back to userspace
> you try to loop but wait routines always keep returning ERESTARTSYS
> once the signal is marked.
> On out of memory conditions TTM module try to move objects to system
> memory and QXL assure surface is updated before the move.
> The fix handle differently this case using no interruptible wait so
> wait functions will wait instead of returning ERESTARTSYS.
> Note the when the loop occurs driver will send a lot of update requests
> causing more CPU usage on Qemu side too.
I actually don't think we should be enabling surfaces upstream, I
don't mind fixing
the kernel driver to not be crap, but I really don't think surfaces
really help the
SPICE protocol.
I should h ave pushed the disable surface in all cases upstream, feel free to do
so, they were a bad experiment, and nobody ever showed they were faster, or
at least when they hit eviction paths they didn't plummet down the
side of a massive
cliff.
The reason this loops in -ERESTARTSYS is that the hw craps itself if you try
and redo an operation, so you can't go back out to userspace and re-enter the
kernel, just one of many bad design points in the QXL hw.
you should probably drop wait_for_io_cmd completely.
Dave.
>
> Signed-off-by: Frediano Ziglio <fziglio@...hat.com>
> ---
> qxl/qxl_cmd.c | 12 +++---------
> qxl/qxl_drv.h | 2 +-
> qxl/qxl_ioctl.c | 2 +-
> 3 files changed, 5 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/gpu/drm/drivers/gpu/drm/qxl/qxl_cmd.c b/qxl/qxl_cmd.c
> index 9782364..bd5404e 100644
> --- a/drivers/gpu/drm/qxl/qxl_cmd.c
> +++ b/drivers/gpu/drm/qxl/qxl_cmd.c
> @@ -317,14 +317,11 @@ static void wait_for_io_cmd(struct qxl_device *qdev, uint8_t val, long port)
> {
> int ret;
>
> -restart:
> ret = wait_for_io_cmd_user(qdev, val, port, false);
> - if (ret == -ERESTARTSYS)
> - goto restart;
> }
>
> int qxl_io_update_area(struct qxl_ddevice *qdev, struct qxl_bo *surf,
> - const struct qxl_rect *area)
> + const struct qxl_rect *area, bool intr)
> {
> int surface_id;
> uint32_t surface_width, surface_height;
> @@ -350,7 +347,7 @@ int qxl_io_update_area(struct qxl_device *qdev, struct qxl_bo *surf,
> mutex_lock(&qdev->update_area_mutex);
> qdev->ram_header->update_area = *area;
> qdev->ram_header->update_surface = surface_id;
> - ret = wait_for_io_cmd_user(qdev, 0, QXL_IO_UPDATE_AREA_ASYNC, true);
> + ret = wait_for_io_cmd_user(qdev, 0, QXL_IO_UPDATE_AREA_ASYNC, intr);
> mutex_unlock(&qdev->update_area_mutex);
> return ret;
> }
> @@ -588,10 +585,7 @@ int qxl_update_surface(struct qxl_device *qdev, struct qxl_bo *surf)
> rect.right = surf->surf.width;
> rect.top = 0;
> rect.bottom = surf->surf.height;
> -retry:
> - ret = qxl_io_update_area(qdev, surf, &rect);
> - if (ret == -ERESTARTSYS)
> - goto retry;
> + ret = qxl_io_update_area(qdev, surf, &rect, false);
> return ret;
> }
>
> diff --git a/drivers/gpu/drm/drivers/gpu/drm/qxl/qxl_drv.h b/qxl/qxl_drv.h
> index 7c6cafe..6745c44 100644
> --- a/drivers/gpu/drm/qxl/qxl_drv.h
> +++ b/drivers/gpu/drm/qxl/qxl_drv.h
> @@ -462,7 +462,7 @@ void qxl_io_memslot_add(struct qxl_device *qdev, uint8_t id);
> void qxl_io_notify_oom(struct qxl_device *qdev);
>
> int qxl_io_update_area(struct qxl_device *qdev, struct qxl_bo *surf,
> - const struct qxl_rect *area);
> + const struct qxl_rect *area, bool intr);
>
> void qxl_io_reset(struct qxl_device *qdev);
> void qxl_io_monitors_config(struct qxl_device *qdev);
> diff --git a/drivers/gpu/drm/qxl/qxl_ioctl.c b/qxl/qxl_ioctl.c
> index b110883..afd7297 100644
> --- a/drivers/gpu/drm/qxl/qxl_ioctl.c
> +++ b/drivers/gpu/drm/qxl/qxl_ioctl.c
> @@ -348,7 +348,7 @@ static int qxl_update_area_ioctl(struct drm_device *dev, void *data,
> goto out2;
> if (!qobj->surface_id)
> DRM_ERROR("got update area for surface with no id %d\n", update_area->handle);
> - ret = qxl_io_update_area(qdev, qobj, &area);
> + ret = qxl_io_update_area(qdev, qobj, &area, true);
>
> out2:
> qxl_bo_unreserve(qobj);
> --
> 2.1.0
> _______________________________________________
> Spice-devel mailing list
> Spice-devel@...ts.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/spice-devel
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