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drm/i915: Use trace_printk to provide a death rattle for GEM 

Trying to enable printk debugging for GEM is fraught with the issue of
spam; interactions with HW are very frequent and often boring. However,
one instance where they are not so boring is just before a BUG; here
ftrace provides a facility to dump its ringbuffer on an oops. So for CI
let's enable trace_printk() to capture the last exchanges with HW as a
death rattle.

For example,
[   79.234110] ------------[ cut here ]------------
[   79.234137] kernel BUG at drivers/gpu/drm/i915/intel_lrc.c:907!
[   79.234145] invalid opcode: 0000 [#1] SMP
[   79.234153] Dumping ftrace buffer:
[   79.234158] ---------------------------------
...
[   79.314044] gem_conc-1059    1..s1 79203443us : intel_lrc_irq_handler: bcs0 out[0]: ctx=5.2, seqno=145
[   79.314089] gem_conc-1059    1..s. 79220800us : intel_lrc_irq_handler: bcs0 csb[1/1]: status=0x00000018:0x00000005
[   79.314133] gem_conc-1059    1..s. 79220803us : intel_lrc_irq_handler: bcs0 out[0]: ctx=5.1, seqno=145
[   79.314177] gem_conc-1062    2..s1 79230458us : intel_lrc_irq_handler: bcs0 in[0]:  ctx=8.1, seqno=146
[   79.314220] gem_conc-1062    2..s1 79230515us : intel_lrc_irq_handler: bcs0 in[0]:  ctx=8.2, seqno=147
[   79.314265] gem_conc-1059    1..s1 79230951us : intel_lrc_irq_handler: bcs0 csb[2/3]: status=0x00000012:0x00000008
[   79.314309] gem_conc-1059    1..s1 79230954us : intel_lrc_irq_handler: bcs0 out[0]: ctx=8.2, seqno=147
[   79.314353] gem_conc-1059    1..s1 79230954us : intel_lrc_irq_handler: bcs0 csb[3/3]: status=0x00008002:0x00000008
[   79.314396] gem_conc-1059    1..s1 79230955us : intel_lrc_irq_handler: bcs0 out[0]: ctx=8.1, seqno=147
[   79.314402] ---------------------------------

v2: Tweak the formatting to be more consistent between in/out.
v3: do {} while (0) stub macro protection

Suggested-by: Michał Winiarski <michal.winiarski@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171109143019.16568-1-chris@chris-wilson.co.uk
This commit is contained in:
Chris Wilson 2017-11-09 14:30:19 +00:00
parent 2f7734770c
commit bccd3b8311
3 changed files with 37 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
drivers/gpu/drm/i915/Kconfig.debug
View File

@ -28,6 +28,7 @@ config DRM_I915_DEBUG
select SW_SYNC # signaling validation framework (igt/syncobj*)
select DRM_I915_SW_FENCE_DEBUG_OBJECTS
select DRM_I915_SELFTEST
select DRM_I915_TRACE_GEM
default n
help
Choose this option to turn on extra driver debugging that may affect
@ -49,6 +50,19 @@ config DRM_I915_DEBUG_GEM
If in doubt, say "N".
config DRM_I915_TRACE_GEM
bool "Insert extra ftrace output from the GEM internals"
select TRACING
default n
help
Enable additional and verbose debugging output that will spam
ordinary tests, but may be vital for post-mortem debugging when
used with /proc/sys/kernel/ftrace_dump_on_oops
Recommended for driver developers only.
If in doubt, say "N".
config DRM_I915_SW_FENCE_DEBUG_OBJECTS
bool "Enable additional driver debugging for fence objects"
depends on DRM_I915

6
drivers/gpu/drm/i915/i915_gem.h
View File

@ -44,6 +44,12 @@
#define GEM_DEBUG_BUG_ON(expr)
#endif
#if IS_ENABLED(CONFIG_DRM_I915_TRACE_GEM)
#define GEM_TRACE(...) trace_printk(__VA_ARGS__)
#else
#define GEM_TRACE(...) do { } while (0)
#endif
#define I915_NUM_ENGINES 5
#endif /* __I915_GEM_H__ */

17
drivers/gpu/drm/i915/intel_lrc.c
View File

@ -466,6 +466,11 @@ static void execlists_submit_ports(struct intel_engine_cs *engine)
port_set(&port[n], port_pack(rq, count));
desc = execlists_update_context(rq);
GEM_DEBUG_EXEC(port[n].context_id = upper_32_bits(desc));
GEM_TRACE("%s in[%d]: ctx=%d.%d, seqno=%x\n",
engine->name, n,
rq->ctx->hw_id, count,
rq->global_seqno);
} else {
GEM_BUG_ON(!n);
desc = 0;
@ -520,6 +525,7 @@ static void inject_preempt_context(struct intel_engine_cs *engine)
ce->ring->tail &= (ce->ring->size - 1);
ce->lrc_reg_state[CTX_RING_TAIL+1] = ce->ring->tail;
GEM_TRACE("\n");
for (n = execlists_num_ports(&engine->execlists); --n; )
elsp_write(0, elsp);
@ -832,6 +838,10 @@ static void intel_lrc_irq_handler(unsigned long data)
head = execlists->csb_head;
tail = READ_ONCE(buf[write_idx]);
}
GEM_TRACE("%s cs-irq head=%d [%d], tail=%d [%d]\n",
engine->name,
head, GEN8_CSB_READ_PTR(readl(dev_priv->regs + i915_mmio_reg_offset(RING_CONTEXT_STATUS_PTR(engine)))),
tail, GEN8_CSB_WRITE_PTR(readl(dev_priv->regs + i915_mmio_reg_offset(RING_CONTEXT_STATUS_PTR(engine)))));
while (head != tail) {
struct drm_i915_gem_request *rq;
@ -859,6 +869,9 @@ static void intel_lrc_irq_handler(unsigned long data)
*/
status = READ_ONCE(buf[2 * head]); /* maybe mmio! */
GEM_TRACE("%s csb[%dd]: status=0x%08x:0x%08x\n",
engine->name, head,
status, buf[2*head + 1]);
if (!(status & GEN8_CTX_STATUS_COMPLETED_MASK))
continue;
@ -886,6 +899,10 @@ static void intel_lrc_irq_handler(unsigned long data)
GEM_DEBUG_BUG_ON(buf[2 * head + 1] != port->context_id);
rq = port_unpack(port, &count);
GEM_TRACE("%s out[0]: ctx=%d.%d, seqno=%x\n",
engine->name,
rq->ctx->hw_id, count,
rq->global_seqno);
GEM_BUG_ON(count == 0);
if (--count == 0) {
GEM_BUG_ON(status & GEN8_CTX_STATUS_PREEMPTED);