[PATCH 5/7] drm/i915/guc: Add stall timer to non blocking CTB send function
Matthew Brost
matthew.brost at intel.com
Thu Jul 1 00:36:24 UTC 2021
On Thu, Jul 01, 2021 at 01:23:36AM +0200, Michal Wajdeczko wrote:
>
>
> On 28.06.2021 01:14, Matthew Brost wrote:
> > Implement a stall timer which fails H2G CTBs once a period of time
> > with no forward progress is reached to prevent deadlock.
> >
> > v2:
> > (Michal)
> > - Improve error message in ct_deadlock()
> > - Set broken when ct_deadlock() returns true
> > - Return -EPIPE on ct_deadlock()
> >
> > Signed-off-by: John Harrison <John.C.Harrison at Intel.com>
> > Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
> > Signed-off-by: Matthew Brost <matthew.brost at intel.com>
> > ---
> > drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c | 62 ++++++++++++++++++++---
> > drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h | 4 ++
> > 2 files changed, 59 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
> > index 90ee95a240e8..8f553f7f9619 100644
> > --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
> > +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
> > @@ -319,6 +319,7 @@ int intel_guc_ct_enable(struct intel_guc_ct *ct)
> > goto err_deregister;
> >
> > ct->enabled = true;
> > + ct->stall_time = KTIME_MAX;
> >
> > return 0;
> >
> > @@ -391,9 +392,6 @@ static int ct_write(struct intel_guc_ct *ct,
> > u32 *cmds = ctb->cmds;
> > unsigned int i;
> >
> > - if (unlikely(ctb->broken))
> > - return -EPIPE;
> > -
> > if (unlikely(desc->status))
> > goto corrupted;
> >
> > @@ -509,6 +507,25 @@ static int wait_for_ct_request_update(struct ct_request *req, u32 *status)
> > return err;
> > }
> >
> > +#define GUC_CTB_TIMEOUT_MS 1500
> > +static inline bool ct_deadlocked(struct intel_guc_ct *ct)
> > +{
> > + long timeout = GUC_CTB_TIMEOUT_MS;
> > + bool ret = ktime_ms_delta(ktime_get(), ct->stall_time) > timeout;
> > +
> > + if (unlikely(ret)) {
> > + struct guc_ct_buffer_desc *send = ct->ctbs.send.desc;
> > + struct guc_ct_buffer_desc *recv = ct->ctbs.send.desc;
> > +
> > + CT_ERROR(ct, "Communication stalled for %lld, desc status=%#x,%#x\n",
>
> nit: missing unit in "stalled for ... ms"
> ^^^^
Yep, will fix.
>
> > + ktime_ms_delta(ktime_get(), ct->stall_time),
> > + send->status, recv->status);
> > + ct->ctbs.send.broken = true;
> > + }
> > +
> > + return ret;
> > +}
> > +
> > static inline bool h2g_has_room(struct intel_guc_ct_buffer *ctb, u32 len_dw)
> > {
> > struct guc_ct_buffer_desc *desc = ctb->desc;
> > @@ -520,6 +537,26 @@ static inline bool h2g_has_room(struct intel_guc_ct_buffer *ctb, u32 len_dw)
> > return space >= len_dw;
> > }
> >
> > +static int has_room_nb(struct intel_guc_ct *ct, u32 len_dw)
> > +{
> > + struct intel_guc_ct_buffer *ctb = &ct->ctbs.send;
> > +
> > + lockdep_assert_held(&ct->ctbs.send.lock);
> > +
> > + if (unlikely(!h2g_has_room(ctb, len_dw))) {
> > + if (ct->stall_time == KTIME_MAX)
> > + ct->stall_time = ktime_get();
> > +
> > + if (unlikely(ct_deadlocked(ct)))
> > + return -EPIPE;
> > + else
> > + return -EBUSY;
> > + }
> > +
> > + ct->stall_time = KTIME_MAX;
> > + return 0;
> > +}
> > +
> > static int ct_send_nb(struct intel_guc_ct *ct,
> > const u32 *action,
> > u32 len,
> > @@ -530,13 +567,14 @@ static int ct_send_nb(struct intel_guc_ct *ct,
> > u32 fence;
> > int ret;
> >
> > + if (unlikely(ctb->broken))
> > + return -EPIPE;
> > +
> > spin_lock_irqsave(&ctb->lock, spin_flags);
> >
> > - ret = h2g_has_room(ctb, len + GUC_CTB_HDR_LEN);
> > - if (unlikely(!ret)) {
> > - ret = -EBUSY;
> > + ret = has_room_nb(ct, len + GUC_CTB_HDR_LEN);
> > + if (unlikely(ret))
> > goto out;
> > - }
> >
> > fence = ct_get_next_fence(ct);
> > ret = ct_write(ct, action, len, fence, flags);
> > @@ -571,6 +609,9 @@ static int ct_send(struct intel_guc_ct *ct,
> > GEM_BUG_ON(!response_buf && response_buf_size);
> > might_sleep();
> >
> > + if (unlikely(ctb->broken))
> > + return -EPIPE;
>
> ok, but likely could be part of ct_can_send/has_room
>
No, this actually should be apart of 'intel_guc_ct_send'.
> > +
> > /*
> > * We use a lazy spin wait loop here as we believe that if the CT
> > * buffers are sized correctly the flow control condition should be
> > @@ -579,8 +620,13 @@ static int ct_send(struct intel_guc_ct *ct,
> > retry:
> > spin_lock_irqsave(&ctb->lock, flags);
> > if (unlikely(!h2g_has_room(ctb, len + GUC_CTB_HDR_LEN))) {
> > + if (ct->stall_time == KTIME_MAX)
> > + ct->stall_time = ktime_get();
> > spin_unlock_irqrestore(&ctb->lock, flags);
> >
> > + if (unlikely(ct_deadlocked(ct)))
> > + return -EPIPE;
> > +
>
> can't we really put all this into one place?
>
Maybe? IMO a helper with arguments might be worse that inline code
depending on how it looks in the end. Now that you mention this I
realize the patch that handles G2H credits is wrong as we really need to
reserve credits here too. When I rework that patch, I'll revisit this.
Matt
> static int ct_can_send(struct intel_guc_ct *ct, u32 len_dw, bool wait)
> {
> struct intel_guc_ct_buffer *ctb = &ct->ctbs.send;
>
> lockdep_assert_held(&ct->ctbs.send.lock);
>
> retry:
> if (ct->broken)
> return -EPIPE;
>
> if (unlikely(!ctb_has_room(ctb, len_dw + GUC_CTB_HDR_LEN))) {
> if (ct->stall_time == KTIME_MAX)
> ct->stall_time = ktime_get();
>
> if (unlikely(ct_deadlocked(ct)))
> return -EPIPE;
> if (!wait)
> return -EBUSY;
>
> spin_unlock_irqrestore(&ctb->lock, flags);
> ...
> spin_lock_irqrestore(&ctb->lock, flags);
>
> goto retry;
> }
>
> ct->stall_time = KTIME_MAX;
> return 0;
> }
>
> Michal
>
> > if (msleep_interruptible(sleep_period_ms))
> > return -EINTR;
> > sleep_period_ms = sleep_period_ms << 1;
> > @@ -588,6 +634,8 @@ static int ct_send(struct intel_guc_ct *ct,
> > goto retry;
> > }
> >
> > + ct->stall_time = KTIME_MAX;
> > +
> > fence = ct_get_next_fence(ct);
> > request.fence = fence;
> > request.status = 0;
> > diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h
> > index f6a4d5b33467..c9d6ae7848a7 100644
> > --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h
> > +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h
> > @@ -9,6 +9,7 @@
> > #include <linux/interrupt.h>
> > #include <linux/spinlock.h>
> > #include <linux/workqueue.h>
> > +#include <linux/ktime.h>
> >
> > #include "intel_guc_fwif.h"
> >
> > @@ -68,6 +69,9 @@ struct intel_guc_ct {
> > struct list_head incoming; /* incoming requests */
> > struct work_struct worker; /* handler for incoming requests */
> > } requests;
> > +
> > + /** @stall_time: time of first time a CTB submission is stalled */
> > + ktime_t stall_time;
> > };
> >
> > void intel_guc_ct_init_early(struct intel_guc_ct *ct);
> >
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