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* [PATCH v3] drm/i915/gt: Use poll_timeout_us in place of sliding sleep window
@ 2026-06-30 15:25 Jonathan Cavitt
  2026-06-30 20:02 ` ✗ i915.CI.BAT: failure for drm/i915/gt: Use poll_timeout_us in place of sliding sleep window (rev3) Patchwork
                   ` (2 more replies)
  0 siblings, 3 replies; 6+ messages in thread
From: Jonathan Cavitt @ 2026-06-30 15:25 UTC (permalink / raw)
  To: intel-gfx; +Cc: alex.zuo, jonathan.cavitt, jani.nikula, andi.shyti

The functions intel_guc_send_busy_loop and ct_send can theoretically
loop forever.  In the former case, intel_guc_send_busy_loop can iterate
forever if intel_guc_send_nb repeatedly returns -EBUSY.  In the latter
case, ct_send can loop forever if the guc-to-host or host-to-guc buffers
get stuck in a full state.

Rework the functions to use the poll_timeout_us family of functions
instead of calculating sleep_period_ms repeatedly.  In both cases now,
if the loop condition is not met after 10 minutes, the function will
report it as a failure.

This also resolves a static analysis issue involving sleep_period_ms
overflowing after several shift-left-logical calls.

v2:
- Reduce default sleep/udelay duration (jcavitt)

v3:
- Use atomic in ct_send (jcavitt)

Suggested-by: Jani Nikula <jani.nikula@linux.intel.com>
Signed-off-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
Cc: Andi Shyti <andi.shyti@intel.com>
---
 drivers/gpu/drm/i915/gt/uc/intel_guc.h    | 32 +++++++++++------------
 drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c | 19 +++++---------
 2 files changed, 23 insertions(+), 28 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc.h b/drivers/gpu/drm/i915/gt/uc/intel_guc.h
index 053780f562c1..13be4f7e7ab7 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc.h
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc.h
@@ -7,6 +7,7 @@
 #define _INTEL_GUC_H_
 
 #include <linux/delay.h>
+#include <linux/iopoll.h>
 #include <linux/iosys-map.h>
 #include <linux/xarray.h>
 
@@ -360,8 +361,7 @@ static inline int intel_guc_send_busy_loop(struct intel_guc *guc,
 					   u32 g2h_len_dw,
 					   bool loop)
 {
-	int err;
-	unsigned int sleep_period_ms = 1;
+	int err, timedout;
 	bool not_atomic = !in_atomic() && !irqs_disabled();
 
 	/*
@@ -374,20 +374,20 @@ static inline int intel_guc_send_busy_loop(struct intel_guc *guc,
 	/* No sleeping with spin locks, just busy loop */
 	might_sleep_if(loop && not_atomic);
 
-retry:
-	err = intel_guc_send_nb(guc, action, len, g2h_len_dw);
-	if (unlikely(err == -EBUSY && loop)) {
-		if (likely(not_atomic)) {
-			if (msleep_interruptible(sleep_period_ms))
-				return -EINTR;
-			sleep_period_ms = sleep_period_ms << 1;
-		} else {
-			cpu_relax();
-		}
-		goto retry;
-	}
-
-	return err;
+	if (!loop)
+		return intel_guc_send_nb(guc, action, len, g2h_len_dw);
+
+	if (not_atomic)
+		timedout = poll_timeout_us(err = intel_guc_send_nb(guc, action,
+								   len, g2h_len_dw),
+					   err != -EBUSY, USEC_PER_MSEC,
+					   600 * USEC_PER_SEC, false);
+	else
+		timedout = poll_timeout_us_atomic(err = intel_guc_send_nb(guc, action,
+									  len, g2h_len_dw),
+						  err != -EBUSY, USEC_PER_MSEC,
+						  600 * USEC_PER_SEC, false);
+	return timedout ?: err;
 }
 
 /* Only call this from the interrupt handler code */
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 1c455d84bf9d..dc4a5486b42c 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
@@ -716,7 +716,6 @@ static int ct_send(struct intel_guc_ct *ct,
 	struct intel_guc_ct_buffer *ctb = &ct->ctbs.send;
 	struct ct_request request;
 	unsigned long flags;
-	unsigned int sleep_period_ms = 1;
 	bool send_again;
 	u32 fence;
 	int err;
@@ -736,22 +735,18 @@ static int ct_send(struct intel_guc_ct *ct,
 	 * rare. Reserving the maximum size in the G2H credits as we don't know
 	 * how big the response is going to be.
 	 */
-retry:
 	spin_lock_irqsave(&ctb->lock, flags);
-	if (unlikely(!h2g_has_room(ct, len + GUC_CTB_HDR_LEN) ||
-		     !g2h_has_room(ct, GUC_CTB_HXG_MSG_MAX_LEN))) {
+	err = poll_timeout_us_atomic(err = 0,
+				     !h2g_has_room(ct, len + GUC_CTB_HDR_LEN) ||
+				     !g2h_has_room(ct, GUC_CTB_HXG_MSG_MAX_LEN),
+				     USEC_PER_MSEC, 600 * USEC_PER_SEC, false);
+
+	if (err) {
 		if (ct->stall_time == KTIME_MAX)
 			ct->stall_time = ktime_get();
 		spin_unlock_irqrestore(&ctb->lock, flags);
 
-		if (unlikely(ct_deadlocked(ct)))
-			return -EPIPE;
-
-		if (msleep_interruptible(sleep_period_ms))
-			return -EINTR;
-		sleep_period_ms = sleep_period_ms << 1;
-
-		goto retry;
+		return unlikely(ct_deadlocked(ct)) ? -EPIPE : err;
 	}
 
 	ct->stall_time = KTIME_MAX;
-- 
2.53.0


^ permalink raw reply related	[flat|nested] 6+ messages in thread
end of thread, other threads:[~2026-07-03 15:12 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-06-30 15:25 [PATCH v3] drm/i915/gt: Use poll_timeout_us in place of sliding sleep window Jonathan Cavitt
2026-06-30 20:02 ` ✗ i915.CI.BAT: failure for drm/i915/gt: Use poll_timeout_us in place of sliding sleep window (rev3) Patchwork
2026-07-01  8:36 ` [PATCH v3] drm/i915/gt: Use poll_timeout_us in place of sliding sleep window Krzysztof Karas
2026-07-01 14:10   ` Cavitt, Jonathan
2026-07-02  6:26     ` Krzysztof Karas
2026-07-03 15:12 ` Andi Shyti

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