diff options
| -rw-r--r-- | drivers/gpu/drm/Kconfig | 14 | ||||
| -rw-r--r-- | drivers/gpu/drm/drm_dp_mst_topology.c | 234 | ||||
| -rw-r--r-- | include/drm/drm_dp_mst_helper.h | 45 |
3 files changed, 285 insertions, 8 deletions
diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig index caeef11976e8..933b916a99e3 100644 --- a/drivers/gpu/drm/Kconfig +++ b/drivers/gpu/drm/Kconfig @@ -93,6 +93,20 @@ config DRM_KMS_FB_HELPER help FBDEV helpers for KMS drivers. +config DRM_DEBUG_DP_MST_TOPOLOGY_REFS + bool "Enable refcount backtrace history in the DP MST helpers" + select STACKDEPOT + depends on DRM_KMS_HELPER + depends on DEBUG_KERNEL + depends on EXPERT + help + Enables debug tracing for topology refs in DRM's DP MST helpers. A + history of each topology reference/dereference will be printed to the + kernel log once a port or branch device's topology refcount reaches 0. + + This has the potential to use a lot of memory and print some very + large kernel messages. If in doubt, say "N". + config DRM_FBDEV_EMULATION bool "Enable legacy fbdev support for your modesetting driver" depends on DRM diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index 42eac2a59a4b..0a402d58fc5d 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -28,6 +28,13 @@ #include <linux/sched.h> #include <linux/seq_file.h> +#if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS) +#include <linux/stackdepot.h> +#include <linux/sort.h> +#include <linux/timekeeping.h> +#include <linux/math64.h> +#endif + #include <drm/drm_atomic.h> #include <drm/drm_atomic_helper.h> #include <drm/drm_dp_mst_helper.h> @@ -1399,12 +1406,184 @@ drm_dp_mst_put_port_malloc(struct drm_dp_mst_port *port) } EXPORT_SYMBOL(drm_dp_mst_put_port_malloc); +#if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS) + +#define STACK_DEPTH 8 + +static noinline void +__topology_ref_save(struct drm_dp_mst_topology_mgr *mgr, + struct drm_dp_mst_topology_ref_history *history, + enum drm_dp_mst_topology_ref_type type) +{ + struct drm_dp_mst_topology_ref_entry *entry = NULL; + depot_stack_handle_t backtrace; + ulong stack_entries[STACK_DEPTH]; + uint n; + int i; + + n = stack_trace_save(stack_entries, ARRAY_SIZE(stack_entries), 1); + backtrace = stack_depot_save(stack_entries, n, GFP_KERNEL); + if (!backtrace) + return; + + /* Try to find an existing entry for this backtrace */ + for (i = 0; i < history->len; i++) { + if (history->entries[i].backtrace == backtrace) { + entry = &history->entries[i]; + break; + } + } + + /* Otherwise add one */ + if (!entry) { + struct drm_dp_mst_topology_ref_entry *new; + int new_len = history->len + 1; + + new = krealloc(history->entries, sizeof(*new) * new_len, + GFP_KERNEL); + if (!new) + return; + + entry = &new[history->len]; + history->len = new_len; + history->entries = new; + + entry->backtrace = backtrace; + entry->type = type; + entry->count = 0; + } + entry->count++; + entry->ts_nsec = ktime_get_ns(); +} + +static int +topology_ref_history_cmp(const void *a, const void *b) +{ + const struct drm_dp_mst_topology_ref_entry *entry_a = a, *entry_b = b; + + if (entry_a->ts_nsec > entry_b->ts_nsec) + return 1; + else if (entry_a->ts_nsec < entry_b->ts_nsec) + return -1; + else + return 0; +} + +static inline const char * +topology_ref_type_to_str(enum drm_dp_mst_topology_ref_type type) +{ + if (type == DRM_DP_MST_TOPOLOGY_REF_GET) + return "get"; + else + return "put"; +} + +static void +__dump_topology_ref_history(struct drm_dp_mst_topology_ref_history *history, + void *ptr, const char *type_str) +{ + struct drm_printer p = drm_debug_printer(DBG_PREFIX); + char *buf = kzalloc(PAGE_SIZE, GFP_KERNEL); + int i; + + if (!buf) + return; + + if (!history->len) + goto out; + + /* First, sort the list so that it goes from oldest to newest + * reference entry + */ + sort(history->entries, history->len, sizeof(*history->entries), + topology_ref_history_cmp, NULL); + + drm_printf(&p, "%s (%p) topology count reached 0, dumping history:\n", + type_str, ptr); + + for (i = 0; i < history->len; i++) { + const struct drm_dp_mst_topology_ref_entry *entry = + &history->entries[i]; + ulong *entries; + uint nr_entries; + u64 ts_nsec = entry->ts_nsec; + u64 rem_nsec = do_div(ts_nsec, 1000000000); + + nr_entries = stack_depot_fetch(entry->backtrace, &entries); + stack_trace_snprint(buf, PAGE_SIZE, entries, nr_entries, 4); + + drm_printf(&p, " %d %ss (last at %5llu.%06llu):\n%s", + entry->count, + topology_ref_type_to_str(entry->type), + ts_nsec, rem_nsec / 1000, buf); + } + + /* Now free the history, since this is the only time we expose it */ + kfree(history->entries); +out: + kfree(buf); +} + +static __always_inline void +drm_dp_mst_dump_mstb_topology_history(struct drm_dp_mst_branch *mstb) +{ + __dump_topology_ref_history(&mstb->topology_ref_history, mstb, + "MSTB"); +} + +static __always_inline void +drm_dp_mst_dump_port_topology_history(struct drm_dp_mst_port *port) +{ + __dump_topology_ref_history(&port->topology_ref_history, port, + "Port"); +} + +static __always_inline void +save_mstb_topology_ref(struct drm_dp_mst_branch *mstb, + enum drm_dp_mst_topology_ref_type type) +{ + __topology_ref_save(mstb->mgr, &mstb->topology_ref_history, type); +} + +static __always_inline void +save_port_topology_ref(struct drm_dp_mst_port *port, + enum drm_dp_mst_topology_ref_type type) +{ + __topology_ref_save(port->mgr, &port->topology_ref_history, type); +} + +static inline void +topology_ref_history_lock(struct drm_dp_mst_topology_mgr *mgr) +{ + mutex_lock(&mgr->topology_ref_history_lock); +} + +static inline void +topology_ref_history_unlock(struct drm_dp_mst_topology_mgr *mgr) +{ + mutex_unlock(&mgr->topology_ref_history_lock); +} +#else +static inline void +topology_ref_history_lock(struct drm_dp_mst_topology_mgr *mgr) {} +static inline void +topology_ref_history_unlock(struct drm_dp_mst_topology_mgr *mgr) {} +static inline void +drm_dp_mst_dump_mstb_topology_history(struct drm_dp_mst_branch *mstb) {} +static inline void +drm_dp_mst_dump_port_topology_history(struct drm_dp_mst_port *port) {} +#define save_mstb_topology_ref(mstb, type) +#define save_port_topology_ref(port, type) +#endif + static void drm_dp_destroy_mst_branch_device(struct kref *kref) { struct drm_dp_mst_branch *mstb = container_of(kref, struct drm_dp_mst_branch, topology_kref); struct drm_dp_mst_topology_mgr *mgr = mstb->mgr; + drm_dp_mst_dump_mstb_topology_history(mstb); + INIT_LIST_HEAD(&mstb->destroy_next); /* @@ -1442,11 +1621,17 @@ static void drm_dp_destroy_mst_branch_device(struct kref *kref) static int __must_check drm_dp_mst_topology_try_get_mstb(struct drm_dp_mst_branch *mstb) { - int ret = kref_get_unless_zero(&mstb->topology_kref); + int ret; - if (ret) - DRM_DEBUG("mstb %p (%d)\n", mstb, - kref_read(&mstb->topology_kref)); + topology_ref_history_lock(mstb->mgr); + ret = kref_get_unless_zero(&mstb->topology_kref); + if (ret) { + DRM_DEBUG("mstb %p (%d)\n", + mstb, kref_read(&mstb->topology_kref)); + save_mstb_topology_ref(mstb, DRM_DP_MST_TOPOLOGY_REF_GET); + } + + topology_ref_history_unlock(mstb->mgr); return ret; } @@ -1467,9 +1652,14 @@ drm_dp_mst_topology_try_get_mstb(struct drm_dp_mst_branch *mstb) */ static void drm_dp_mst_topology_get_mstb(struct drm_dp_mst_branch *mstb) { + topology_ref_history_lock(mstb->mgr); + + save_mstb_topology_ref(mstb, DRM_DP_MST_TOPOLOGY_REF_GET); WARN_ON(kref_read(&mstb->topology_kref) == 0); kref_get(&mstb->topology_kref); DRM_DEBUG("mstb %p (%d)\n", mstb, kref_read(&mstb->topology_kref)); + + topology_ref_history_unlock(mstb->mgr); } /** @@ -1487,8 +1677,13 @@ static void drm_dp_mst_topology_get_mstb(struct drm_dp_mst_branch *mstb) static void drm_dp_mst_topology_put_mstb(struct drm_dp_mst_branch *mstb) { + topology_ref_history_lock(mstb->mgr); + DRM_DEBUG("mstb %p (%d)\n", mstb, kref_read(&mstb->topology_kref) - 1); + save_mstb_topology_ref(mstb, DRM_DP_MST_TOPOLOGY_REF_PUT); + + topology_ref_history_unlock(mstb->mgr); kref_put(&mstb->topology_kref, drm_dp_destroy_mst_branch_device); } @@ -1498,6 +1693,8 @@ static void drm_dp_destroy_port(struct kref *kref) container_of(kref, struct drm_dp_mst_port, topology_kref); struct drm_dp_mst_topology_mgr *mgr = port->mgr; + drm_dp_mst_dump_port_topology_history(port); + /* There's nothing that needs locking to destroy an input port yet */ if (port->input) { drm_dp_mst_put_port_malloc(port); @@ -1541,12 +1738,17 @@ static void drm_dp_destroy_port(struct kref *kref) static int __must_check drm_dp_mst_topology_try_get_port(struct drm_dp_mst_port *port) { - int ret = kref_get_unless_zero(&port->topology_kref); + int ret; - if (ret) - DRM_DEBUG("port %p (%d)\n", port, - kref_read(&port->topology_kref)); + topology_ref_history_lock(port->mgr); + ret = kref_get_unless_zero(&port->topology_kref); + if (ret) { + DRM_DEBUG("port %p (%d)\n", + port, kref_read(&port->topology_kref)); + save_port_topology_ref(port, DRM_DP_MST_TOPOLOGY_REF_GET); + } + topology_ref_history_unlock(port->mgr); return ret; } @@ -1565,9 +1767,14 @@ drm_dp_mst_topology_try_get_port(struct drm_dp_mst_port *port) */ static void drm_dp_mst_topology_get_port(struct drm_dp_mst_port *port) { + topology_ref_history_lock(port->mgr); + WARN_ON(kref_read(&port->topology_kref) == 0); kref_get(&port->topology_kref); DRM_DEBUG("port %p (%d)\n", port, kref_read(&port->topology_kref)); + save_port_topology_ref(port, DRM_DP_MST_TOPOLOGY_REF_GET); + + topology_ref_history_unlock(port->mgr); } /** @@ -1583,8 +1790,13 @@ static void drm_dp_mst_topology_get_port(struct drm_dp_mst_port *port) */ static void drm_dp_mst_topology_put_port(struct drm_dp_mst_port *port) { + topology_ref_history_lock(port->mgr); + DRM_DEBUG("port %p (%d)\n", port, kref_read(&port->topology_kref) - 1); + save_port_topology_ref(port, DRM_DP_MST_TOPOLOGY_REF_PUT); + + topology_ref_history_unlock(port->mgr); kref_put(&port->topology_kref, drm_dp_destroy_port); } @@ -4578,6 +4790,9 @@ int drm_dp_mst_topology_mgr_init(struct drm_dp_mst_topology_mgr *mgr, mutex_init(&mgr->delayed_destroy_lock); mutex_init(&mgr->up_req_lock); mutex_init(&mgr->probe_lock); +#if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS) + mutex_init(&mgr->topology_ref_history_lock); +#endif INIT_LIST_HEAD(&mgr->tx_msg_downq); INIT_LIST_HEAD(&mgr->destroy_port_list); INIT_LIST_HEAD(&mgr->destroy_branch_device_list); @@ -4644,6 +4859,9 @@ void drm_dp_mst_topology_mgr_destroy(struct drm_dp_mst_topology_mgr *mgr) mutex_destroy(&mgr->lock); mutex_destroy(&mgr->up_req_lock); mutex_destroy(&mgr->probe_lock); +#if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS) + mutex_destroy(&mgr->topology_ref_history_lock); +#endif } EXPORT_SYMBOL(drm_dp_mst_topology_mgr_destroy); diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h index 144027e27464..d5fc90b30487 100644 --- a/include/drm/drm_dp_mst_helper.h +++ b/include/drm/drm_dp_mst_helper.h @@ -26,6 +26,26 @@ #include <drm/drm_dp_helper.h> #include <drm/drm_atomic.h> +#if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS) +#include <linux/stackdepot.h> +#include <linux/timekeeping.h> + +enum drm_dp_mst_topology_ref_type { + DRM_DP_MST_TOPOLOGY_REF_GET, + DRM_DP_MST_TOPOLOGY_REF_PUT, +}; + +struct drm_dp_mst_topology_ref_history { + struct drm_dp_mst_topology_ref_entry { + enum drm_dp_mst_topology_ref_type type; + int count; + ktime_t ts_nsec; + depot_stack_handle_t backtrace; + } *entries; + int len; +}; +#endif /* IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS) */ + struct drm_dp_mst_branch; /** @@ -89,6 +109,14 @@ struct drm_dp_mst_port { */ struct kref malloc_kref; +#if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS) + /** + * @topology_ref_history: A history of each topology + * reference/dereference. See CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS. + */ + struct drm_dp_mst_topology_ref_history topology_ref_history; +#endif + u8 port_num; bool input; bool mcs; @@ -162,6 +190,14 @@ struct drm_dp_mst_branch { */ struct kref malloc_kref; +#if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS) + /** + * @topology_ref_history: A history of each topology + * reference/dereference. See CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS. + */ + struct drm_dp_mst_topology_ref_history topology_ref_history; +#endif + /** * @destroy_next: linked-list entry used by * drm_dp_delayed_destroy_work() @@ -647,6 +683,15 @@ struct drm_dp_mst_topology_mgr { * transmissions. */ struct work_struct up_req_work; + +#if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS) + /** + * @topology_ref_history_lock: protects + * &drm_dp_mst_port.topology_ref_history and + * &drm_dp_mst_branch.topology_ref_history. + */ + struct mutex topology_ref_history_lock; +#endif }; int drm_dp_mst_topology_mgr_init(struct drm_dp_mst_topology_mgr *mgr, |