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Use semaphore to mediate access to DataFlash-over-MAVLink #6003

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merged 2 commits into from Apr 6, 2017
Merged

Use semaphore to mediate access to DataFlash-over-MAVLink #6003

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3cbee43
DataFlash: improve privacy aspects of instance variables
peterbarker Apr 5, 2017
7e68c9f
DataFlash: add mutex for WritePrioritisedBlock
peterbarker Apr 5, 2017
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25 changes: 22 additions & 3 deletions libraries/DataFlash/DataFlash_MAVLink.cpp
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Expand Up @@ -25,6 +25,12 @@ extern const AP_HAL::HAL& hal;
// initialisation
void DataFlash_MAVLink::Init()
{
semaphore = hal.util->new_semaphore();
if (semaphore == nullptr) {
AP_HAL::panic("Failed to create DataFlash_MAVLink semaphore");
return;
}

DataFlash_Backend::Init();

_blocks = nullptr;
Expand Down Expand Up @@ -121,7 +127,13 @@ bool DataFlash_MAVLink::WritePrioritisedBlock(const void *pBuffer, uint16_t size
return false;
}

if (!semaphore->take_nonblocking()) {
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Do we really want to use non-blocking take? Would it be so bad to use it with a 10ms timeout?

dropped++;
return false;
}

if (! WriteBlockCheckStartupMessages()) {
semaphore->give();
return false;
}

Expand All @@ -130,6 +142,7 @@ bool DataFlash_MAVLink::WritePrioritisedBlock(const void *pBuffer, uint16_t size
// do not count the startup packets as being dropped...
dropped++;
}
semaphore->give();
return false;
}

Expand All @@ -141,6 +154,7 @@ bool DataFlash_MAVLink::WritePrioritisedBlock(const void *pBuffer, uint16_t size
if (_current_block == nullptr) {
// should not happen - there's a sanity check above
internal_error();
semaphore->give();
return false;
}
}
Expand All @@ -157,9 +171,7 @@ bool DataFlash_MAVLink::WritePrioritisedBlock(const void *pBuffer, uint16_t size
}
}

if (!_writing_startup_messages) {
// push_log_blocks();
}
semaphore->give();

return true;
}
Expand Down Expand Up @@ -465,13 +477,20 @@ void DataFlash_MAVLink::push_log_blocks()

DataFlash_Backend::WriteMoreStartupMessages();

if (!semaphore->take_nonblocking()) {
return;
}

if (! send_log_blocks_from_queue(_blocks_retry)) {
semaphore->give();
return;
}

if (! send_log_blocks_from_queue(_blocks_pending)) {
semaphore->give();
return;
}
semaphore->give();
}

void DataFlash_MAVLink::do_resends(uint32_t now)
Expand Down
11 changes: 8 additions & 3 deletions libraries/DataFlash/DataFlash_MAVLink.h
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Expand Up @@ -64,19 +64,23 @@ class DataFlash_MAVLink : public DataFlash_Backend
void ShowDeviceInfo(AP_HAL::BetterStream *port) override {}
void ListAvailableLogs(AP_HAL::BetterStream *port) override {}

void push_log_blocks() override;

void remote_log_block_status_msg(mavlink_channel_t chan, mavlink_message_t* msg) override;

private:

struct dm_block {
uint32_t seqno;
uint8_t buf[MAVLINK_MSG_REMOTE_LOG_DATA_BLOCK_FIELD_DATA_LEN];
uint32_t last_sent;
struct dm_block *next;
};
void push_log_blocks();
bool send_log_block(struct dm_block &block);
void handle_ack(mavlink_channel_t chan, mavlink_message_t* msg, uint32_t seqno);
void handle_retry(uint32_t block_num);
void do_resends(uint32_t now);
void set_channel(mavlink_channel_t chan);
void remote_log_block_status_msg(mavlink_channel_t chan, mavlink_message_t* msg) override;
void free_all_blocks();

// a stack for free blocks, queues for pending, sent, retries and sent
Expand All @@ -99,7 +103,6 @@ class DataFlash_MAVLink : public DataFlash_Backend
dm_block_queue_t _blocks_pending;
dm_block_queue_t _blocks_retry;

protected:
struct _stats {
// the following are reset any time we log stats (see "reset_stats")
uint32_t resends;
Expand Down Expand Up @@ -184,6 +187,8 @@ class DataFlash_MAVLink : public DataFlash_Backend
AP_HAL::Util::perf_counter_t _perf_errors;
AP_HAL::Util::perf_counter_t _perf_packing;
AP_HAL::Util::perf_counter_t _perf_overruns;

AP_HAL::Semaphore *semaphore;
};

#endif // DATAFLASH_MAVLINK_SUPPORT