From bd8ef10261d7ae92ad2b4925afd2b56f46175c47 Mon Sep 17 00:00:00 2001 From: Paul Fertser Date: Tue, 28 Jul 2009 00:58:48 +0400 Subject: [PATCH] mfd: revise locking for pcf50633 ADC Current implementation is prone to races, this patch attempts to remove all but one (in pcf50633_adc_sync_read). The idea is that we need to guard the queue access only on inserting and removing items. If we insert and there're no more items in the queue it means that the last irq already happened and we need to trigger ADC manually. If not, then the next conversion will be triggered by the irq handler upon completion of the previous. Signed-off-by: Paul Fertser Signed-off-by: Samuel Ortiz --- drivers/mfd/pcf50633-adc.c | 32 ++++++++++++++++---------------- 1 file changed, 16 insertions(+), 16 deletions(-) diff --git a/drivers/mfd/pcf50633-adc.c b/drivers/mfd/pcf50633-adc.c index c2d05becfa97..3d31e97d6a45 100644 --- a/drivers/mfd/pcf50633-adc.c +++ b/drivers/mfd/pcf50633-adc.c @@ -73,15 +73,10 @@ static void trigger_next_adc_job_if_any(struct pcf50633 *pcf) struct pcf50633_adc *adc = __to_adc(pcf); int head; - mutex_lock(&adc->queue_mutex); - head = adc->queue_head; - if (!adc->queue[head]) { - mutex_unlock(&adc->queue_mutex); + if (!adc->queue[head]) return; - } - mutex_unlock(&adc->queue_mutex); adc_setup(pcf, adc->queue[head]->mux, adc->queue[head]->avg); } @@ -99,16 +94,17 @@ adc_enqueue_request(struct pcf50633 *pcf, struct pcf50633_adc_request *req) if (adc->queue[tail]) { mutex_unlock(&adc->queue_mutex); + dev_err(pcf->dev, "ADC queue is full, dropping request\n"); return -EBUSY; } adc->queue[tail] = req; + if (head == tail) + trigger_next_adc_job_if_any(pcf); adc->queue_tail = (tail + 1) & (PCF50633_MAX_ADC_FIFO_DEPTH - 1); mutex_unlock(&adc->queue_mutex); - trigger_next_adc_job_if_any(pcf); - return 0; } @@ -124,6 +120,7 @@ pcf50633_adc_sync_read_callback(struct pcf50633 *pcf, void *param, int result) int pcf50633_adc_sync_read(struct pcf50633 *pcf, int mux, int avg) { struct pcf50633_adc_request *req; + int err; /* req is freed when the result is ready, in interrupt handler */ req = kzalloc(sizeof(*req), GFP_KERNEL); @@ -136,9 +133,13 @@ int pcf50633_adc_sync_read(struct pcf50633 *pcf, int mux, int avg) req->callback_param = req; init_completion(&req->completion); - adc_enqueue_request(pcf, req); + err = adc_enqueue_request(pcf, req); + if (err) + return err; + wait_for_completion(&req->completion); + /* FIXME by this time req might be already freed */ return req->result; } EXPORT_SYMBOL_GPL(pcf50633_adc_sync_read); @@ -159,9 +160,7 @@ int pcf50633_adc_async_read(struct pcf50633 *pcf, int mux, int avg, req->callback = callback; req->callback_param = callback_param; - adc_enqueue_request(pcf, req); - - return 0; + return adc_enqueue_request(pcf, req); } EXPORT_SYMBOL_GPL(pcf50633_adc_async_read); @@ -184,7 +183,7 @@ static void pcf50633_adc_irq(int irq, void *data) struct pcf50633_adc *adc = data; struct pcf50633 *pcf = adc->pcf; struct pcf50633_adc_request *req; - int head; + int head, res; mutex_lock(&adc->queue_mutex); head = adc->queue_head; @@ -199,12 +198,13 @@ static void pcf50633_adc_irq(int irq, void *data) adc->queue_head = (head + 1) & (PCF50633_MAX_ADC_FIFO_DEPTH - 1); + res = adc_result(pcf); + trigger_next_adc_job_if_any(pcf); + mutex_unlock(&adc->queue_mutex); - req->callback(pcf, req->callback_param, adc_result(pcf)); + req->callback(pcf, req->callback_param, res); kfree(req); - - trigger_next_adc_job_if_any(pcf); } static int __devinit pcf50633_adc_probe(struct platform_device *pdev)