diff options
Diffstat (limited to 'target/linux/brcm2708/patches-4.4/0427-vchiq_arm-Avoid-use-of-mutex-in-add_completion.patch')
| -rw-r--r-- | target/linux/brcm2708/patches-4.4/0427-vchiq_arm-Avoid-use-of-mutex-in-add_completion.patch | 192 |
1 files changed, 192 insertions, 0 deletions
diff --git a/target/linux/brcm2708/patches-4.4/0427-vchiq_arm-Avoid-use-of-mutex-in-add_completion.patch b/target/linux/brcm2708/patches-4.4/0427-vchiq_arm-Avoid-use-of-mutex-in-add_completion.patch new file mode 100644 index 0000000..6dfecc0 --- /dev/null +++ b/target/linux/brcm2708/patches-4.4/0427-vchiq_arm-Avoid-use-of-mutex-in-add_completion.patch @@ -0,0 +1,192 @@ +From 00d6172964200c5d72cef2264ff09d38f764bd69 Mon Sep 17 00:00:00 2001 +From: Phil Elwell <phil@raspberrypi.org> +Date: Mon, 20 Jun 2016 13:51:44 +0100 +Subject: [PATCH] vchiq_arm: Avoid use of mutex in add_completion + +Claiming the completion_mutex within add_completion did prevent some +messages appearing twice, but provokes a deadlock caused by vcsm using +vchiq within a page fault handler. + +Revert the use of completion_mutex, and instead fix the original +problem using more memory barriers. + +Signed-off-by: Phil Elwell <phil@raspberrypi.org> +--- + .../vc04_services/interface/vchiq_arm/vchiq_arm.c | 55 +++++++++++----------- + .../vc04_services/interface/vchiq_arm/vchiq_core.c | 14 ++++-- + 2 files changed, 37 insertions(+), 32 deletions(-) + +--- a/drivers/misc/vc04_services/interface/vchiq_arm/vchiq_arm.c ++++ b/drivers/misc/vc04_services/interface/vchiq_arm/vchiq_arm.c +@@ -64,10 +64,10 @@ + #define VCHIQ_MINOR 0 + + /* Some per-instance constants */ +-#define MAX_COMPLETIONS 16 ++#define MAX_COMPLETIONS 128 + #define MAX_SERVICES 64 + #define MAX_ELEMENTS 8 +-#define MSG_QUEUE_SIZE 64 ++#define MSG_QUEUE_SIZE 128 + + #define KEEPALIVE_VER 1 + #define KEEPALIVE_VER_MIN KEEPALIVE_VER +@@ -208,28 +208,24 @@ add_completion(VCHIQ_INSTANCE_T instance + void *bulk_userdata) + { + VCHIQ_COMPLETION_DATA_T *completion; ++ int insert; + DEBUG_INITIALISE(g_state.local) + +- mutex_lock(&instance->completion_mutex); +- +- while (instance->completion_insert == +- (instance->completion_remove + MAX_COMPLETIONS)) { ++ insert = instance->completion_insert; ++ while ((insert - instance->completion_remove) >= MAX_COMPLETIONS) { + /* Out of space - wait for the client */ + DEBUG_TRACE(SERVICE_CALLBACK_LINE); + vchiq_log_trace(vchiq_arm_log_level, + "add_completion - completion queue full"); + DEBUG_COUNT(COMPLETION_QUEUE_FULL_COUNT); + +- mutex_unlock(&instance->completion_mutex); + if (down_interruptible(&instance->remove_event) != 0) { + vchiq_log_info(vchiq_arm_log_level, + "service_callback interrupted"); + return VCHIQ_RETRY; + } + +- mutex_lock(&instance->completion_mutex); + if (instance->closing) { +- mutex_unlock(&instance->completion_mutex); + vchiq_log_info(vchiq_arm_log_level, + "service_callback closing"); + return VCHIQ_SUCCESS; +@@ -237,9 +233,7 @@ add_completion(VCHIQ_INSTANCE_T instance + DEBUG_TRACE(SERVICE_CALLBACK_LINE); + } + +- completion = +- &instance->completions[instance->completion_insert & +- (MAX_COMPLETIONS - 1)]; ++ completion = &instance->completions[insert & (MAX_COMPLETIONS - 1)]; + + completion->header = header; + completion->reason = reason; +@@ -260,12 +254,9 @@ add_completion(VCHIQ_INSTANCE_T instance + wmb(); + + if (reason == VCHIQ_MESSAGE_AVAILABLE) +- user_service->message_available_pos = +- instance->completion_insert; +- +- instance->completion_insert++; ++ user_service->message_available_pos = insert; + +- mutex_unlock(&instance->completion_mutex); ++ instance->completion_insert = ++insert; + + up(&instance->insert_event); + +@@ -795,6 +786,7 @@ vchiq_ioctl(struct file *file, unsigned + instance->completion_insert) + && !instance->closing) { + int rc; ++ + DEBUG_TRACE(AWAIT_COMPLETION_LINE); + mutex_unlock(&instance->completion_mutex); + rc = down_interruptible(&instance->insert_event); +@@ -809,24 +801,29 @@ vchiq_ioctl(struct file *file, unsigned + } + DEBUG_TRACE(AWAIT_COMPLETION_LINE); + +- /* A read memory barrier is needed to stop prefetch of a stale +- ** completion record +- */ +- rmb(); +- + if (ret == 0) { + int msgbufcount = args.msgbufcount; ++ int remove; ++ ++ remove = instance->completion_remove; ++ + for (ret = 0; ret < args.count; ret++) { + VCHIQ_COMPLETION_DATA_T *completion; + VCHIQ_SERVICE_T *service; + USER_SERVICE_T *user_service; + VCHIQ_HEADER_T *header; +- if (instance->completion_remove == +- instance->completion_insert) ++ ++ if (remove == instance->completion_insert) + break; ++ + completion = &instance->completions[ +- instance->completion_remove & +- (MAX_COMPLETIONS - 1)]; ++ remove & (MAX_COMPLETIONS - 1)]; ++ ++ ++ /* A read memory barrier is needed to prevent ++ ** the prefetch of a stale completion record ++ */ ++ rmb(); + + service = completion->service_userdata; + user_service = service->base.userdata; +@@ -903,7 +900,11 @@ vchiq_ioctl(struct file *file, unsigned + break; + } + +- instance->completion_remove++; ++ /* Ensure that the above copy has completed ++ ** before advancing the remove pointer. */ ++ mb(); ++ ++ instance->completion_remove = ++remove; + } + + if (msgbufcount != args.msgbufcount) { +--- a/drivers/misc/vc04_services/interface/vchiq_arm/vchiq_core.c ++++ b/drivers/misc/vc04_services/interface/vchiq_arm/vchiq_core.c +@@ -610,15 +610,15 @@ process_free_queue(VCHIQ_STATE_T *state) + BITSET_T service_found[BITSET_SIZE(VCHIQ_MAX_SERVICES)]; + int slot_queue_available; + +- /* Use a read memory barrier to ensure that any state that may have +- ** been modified by another thread is not masked by stale prefetched +- ** values. */ +- rmb(); +- + /* Find slots which have been freed by the other side, and return them + ** to the available queue. */ + slot_queue_available = state->slot_queue_available; + ++ /* Use a memory barrier to ensure that any state that may have been ++ ** modified by another thread is not masked by stale prefetched ++ ** values. */ ++ mb(); ++ + while (slot_queue_available != local->slot_queue_recycle) { + unsigned int pos; + int slot_index = local->slot_queue[slot_queue_available++ & +@@ -626,6 +626,8 @@ process_free_queue(VCHIQ_STATE_T *state) + char *data = (char *)SLOT_DATA_FROM_INDEX(state, slot_index); + int data_found = 0; + ++ rmb(); ++ + vchiq_log_trace(vchiq_core_log_level, "%d: pfq %d=%x %x %x", + state->id, slot_index, (unsigned int)data, + local->slot_queue_recycle, slot_queue_available); +@@ -741,6 +743,8 @@ process_free_queue(VCHIQ_STATE_T *state) + up(&state->data_quota_event); + } + ++ mb(); ++ + state->slot_queue_available = slot_queue_available; + up(&state->slot_available_event); + } |