>
> Hey,
>
> On Tue, May 19, 2015 at 05:54:54AM -0400, Frediano Ziglio 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.
> >
> > Signed-off-by: Frediano Ziglio <fziglio@xxxxxxxxxx>
> > ---
> > 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;
>
> I think this one is not directly related to the fix, but can be removed
> because wait_for_io_cmd_user(qdev, val, port, false); will call
> wait_event_timeout() which cannot return ERESTARTSYS? Or was this loop
> causing issues too?
>
Yes, but it has the same issue. Try till ERESTARTSYS are gone.
Currently perhaps not broken but prone to have same issue.
> > }
> >
> > 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)
> > {
> > 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);
>
> My understanding is that the fix is this hunk? If so, this could be made
> more obvious with an intermediate commit adding the 'bool intr' arg to
> qxl_io_update_area and only calling it with 'true' in the appropriate
> places.
> This code path is only triggered from qxl_surface_evict() which I assume
> is not necessarily easily interruptible, so this change makes sense to
> me. However it would be much better to get a review from Dave Airlie ;)
>
> Christophe
>
Are you asking if just removing the loop would fix the issue?
So you are proposing a first patch that add the argument always passing true and another that change some calls to false? It make sense but still the loop should be removed.
Frediano
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