There are two problems in panthor's cache flushing/soft reset code related to locking.
The first problem is that the spinlocks are taken with _irqsave, even though the contended lock is never acquired in a raw interrupt handler. Only a threaded handler locks it. The second problem is that the wait_event condition references pending_reqs without holding the required lock. This means there's a data race. While resolving the first problem is easy, the second problem requires adding some more macro variants to wait.h, which is done in the first patch. New tracepoints to debug cache flushing duration without initial locking waits is thrown in for good measure as well, to complement what's in lock_stat and what the function tracer can already do. Signed-off-by: Nicolas Frattaroli <[email protected]> --- Changes in v3: - Drop new wait_event macro patch as the existing ones have a memory barrier that makes the current use valid - Rewrite fix patch to use scoped guards, and just get rid of the IRQ disabling - Add separate fix for the outside-of-lock pending_reqs clearing in soft reset path - Move tracepoint patch to before fixes for easier before/after testing - Link to v2: https://patch.msgid.link/[email protected] Changes in v2: - Use trace event template for the two tracepoints (ty Steven Rostedt) - Link to v1: https://patch.msgid.link/[email protected] --- Nicolas Frattaroli (3): drm/panthor: Add tracepoints for cache flushing drm/panthor: Revisit reqs_lock handling in flush/reset paths drm/panthor: Take reqs_lock in soft_reset for clearing pending_reqs drivers/gpu/drm/panthor/panthor_gpu.c | 70 +++++++++++++++++---------------- drivers/gpu/drm/panthor/panthor_trace.h | 49 +++++++++++++++++++++++ 2 files changed, 85 insertions(+), 34 deletions(-) --- base-commit: dc462ab791b686c48545c160ecc81be64f77a846 change-id: 20260728-panthor-cache-flush-fix-b36cb15f92c3 Best regards, -- Nicolas Frattaroli <[email protected]>
