From: Arnd Bergmann Date: Thu, 18 May 2017 20:21:41 +0000 (+0200) Subject: HID: intel_ish-hid: clarify locking in client code X-Git-Tag: v4.13~330^2~1^2~5 X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=538be0aa8610168d7a8f4b119452056f537cff46;p=mirror_ubuntu-artful-kernel.git HID: intel_ish-hid: clarify locking in client code I was trying to understand this code while working on a warning fix and the locking made no sense: spin_lock_irqsave() is pointless when run inside of an interrupt handler or nested inside of another spin_lock_irq() or spin_lock_irqsave(). Here it turned out that the comment above the function is wrong, as both recv_ishtp_cl_msg_dma() and recv_ishtp_cl_msg() can in fact be called from a work queue rather than an ISR, so we do have to use the irqsave() version once. This fixes the comments accordingly, removes the misleading 'dev_flags' variable and modifies the inner spinlock to not use 'irqsave'. No functional change is intended, this is just for readability and it slightly simplifies the object code. Signed-off-by: Arnd Bergmann Acked-by: Srinivas Pandruvada Signed-off-by: Jiri Kosina --- diff --git a/drivers/hid/intel-ish-hid/ishtp/client.c b/drivers/hid/intel-ish-hid/ishtp/client.c index 78d393e616a4..f54689ee67e1 100644 --- a/drivers/hid/intel-ish-hid/ishtp/client.c +++ b/drivers/hid/intel-ish-hid/ishtp/client.c @@ -803,7 +803,7 @@ void ishtp_cl_send_msg(struct ishtp_device *dev, struct ishtp_cl *cl) * @ishtp_hdr: Pointer to message header * * Receive and dispatch ISHTP client messages. This function executes in ISR - * context + * or work queue context */ void recv_ishtp_cl_msg(struct ishtp_device *dev, struct ishtp_msg_hdr *ishtp_hdr) @@ -813,7 +813,6 @@ void recv_ishtp_cl_msg(struct ishtp_device *dev, struct ishtp_cl_rb *new_rb; unsigned char *buffer = NULL; struct ishtp_cl_rb *complete_rb = NULL; - unsigned long dev_flags; unsigned long flags; int rb_count; @@ -828,7 +827,7 @@ void recv_ishtp_cl_msg(struct ishtp_device *dev, goto eoi; } - spin_lock_irqsave(&dev->read_list_spinlock, dev_flags); + spin_lock_irqsave(&dev->read_list_spinlock, flags); rb_count = -1; list_for_each_entry(rb, &dev->read_list.list, list) { ++rb_count; @@ -840,8 +839,7 @@ void recv_ishtp_cl_msg(struct ishtp_device *dev, /* If no Rx buffer is allocated, disband the rb */ if (rb->buffer.size == 0 || rb->buffer.data == NULL) { - spin_unlock_irqrestore(&dev->read_list_spinlock, - dev_flags); + spin_unlock_irqrestore(&dev->read_list_spinlock, flags); dev_err(&cl->device->dev, "Rx buffer is not allocated.\n"); list_del(&rb->list); @@ -857,8 +855,7 @@ void recv_ishtp_cl_msg(struct ishtp_device *dev, * back FC, so communication will be stuck anyway) */ if (rb->buffer.size < ishtp_hdr->length + rb->buf_idx) { - spin_unlock_irqrestore(&dev->read_list_spinlock, - dev_flags); + spin_unlock_irqrestore(&dev->read_list_spinlock, flags); dev_err(&cl->device->dev, "message overflow. size %d len %d idx %ld\n", rb->buffer.size, ishtp_hdr->length, @@ -884,14 +881,13 @@ void recv_ishtp_cl_msg(struct ishtp_device *dev, * the whole msg arrived, send a new FC, and add a new * rb buffer for the next coming msg */ - spin_lock_irqsave(&cl->free_list_spinlock, flags); + spin_lock(&cl->free_list_spinlock); if (!list_empty(&cl->free_rb_list.list)) { new_rb = list_entry(cl->free_rb_list.list.next, struct ishtp_cl_rb, list); list_del_init(&new_rb->list); - spin_unlock_irqrestore(&cl->free_list_spinlock, - flags); + spin_unlock(&cl->free_list_spinlock); new_rb->cl = cl; new_rb->buf_idx = 0; INIT_LIST_HEAD(&new_rb->list); @@ -900,8 +896,7 @@ void recv_ishtp_cl_msg(struct ishtp_device *dev, ishtp_hbm_cl_flow_control_req(dev, cl); } else { - spin_unlock_irqrestore(&cl->free_list_spinlock, - flags); + spin_unlock(&cl->free_list_spinlock); } } /* One more fragment in message (even if this was last) */ @@ -914,7 +909,7 @@ void recv_ishtp_cl_msg(struct ishtp_device *dev, break; } - spin_unlock_irqrestore(&dev->read_list_spinlock, dev_flags); + spin_unlock_irqrestore(&dev->read_list_spinlock, flags); /* If it's nobody's message, just read and discard it */ if (!buffer) { uint8_t rd_msg_buf[ISHTP_RD_MSG_BUF_SIZE]; @@ -941,7 +936,7 @@ eoi: * @hbm: hbm buffer * * Receive and dispatch ISHTP client messages using DMA. This function executes - * in ISR context + * in ISR or work queue context */ void recv_ishtp_cl_msg_dma(struct ishtp_device *dev, void *msg, struct dma_xfer_hbm *hbm) @@ -951,10 +946,10 @@ void recv_ishtp_cl_msg_dma(struct ishtp_device *dev, void *msg, struct ishtp_cl_rb *new_rb; unsigned char *buffer = NULL; struct ishtp_cl_rb *complete_rb = NULL; - unsigned long dev_flags; unsigned long flags; - spin_lock_irqsave(&dev->read_list_spinlock, dev_flags); + spin_lock_irqsave(&dev->read_list_spinlock, flags); + list_for_each_entry(rb, &dev->read_list.list, list) { cl = rb->cl; if (!cl || !(cl->host_client_id == hbm->host_client_id && @@ -966,8 +961,7 @@ void recv_ishtp_cl_msg_dma(struct ishtp_device *dev, void *msg, * If no Rx buffer is allocated, disband the rb */ if (rb->buffer.size == 0 || rb->buffer.data == NULL) { - spin_unlock_irqrestore(&dev->read_list_spinlock, - dev_flags); + spin_unlock_irqrestore(&dev->read_list_spinlock, flags); dev_err(&cl->device->dev, "response buffer is not allocated.\n"); list_del(&rb->list); @@ -983,8 +977,7 @@ void recv_ishtp_cl_msg_dma(struct ishtp_device *dev, void *msg, * back FC, so communication will be stuck anyway) */ if (rb->buffer.size < hbm->msg_length) { - spin_unlock_irqrestore(&dev->read_list_spinlock, - dev_flags); + spin_unlock_irqrestore(&dev->read_list_spinlock, flags); dev_err(&cl->device->dev, "message overflow. size %d len %d idx %ld\n", rb->buffer.size, hbm->msg_length, rb->buf_idx); @@ -1008,14 +1001,13 @@ void recv_ishtp_cl_msg_dma(struct ishtp_device *dev, void *msg, * the whole msg arrived, send a new FC, and add a new * rb buffer for the next coming msg */ - spin_lock_irqsave(&cl->free_list_spinlock, flags); + spin_lock(&cl->free_list_spinlock); if (!list_empty(&cl->free_rb_list.list)) { new_rb = list_entry(cl->free_rb_list.list.next, struct ishtp_cl_rb, list); list_del_init(&new_rb->list); - spin_unlock_irqrestore(&cl->free_list_spinlock, - flags); + spin_unlock(&cl->free_list_spinlock); new_rb->cl = cl; new_rb->buf_idx = 0; INIT_LIST_HEAD(&new_rb->list); @@ -1024,8 +1016,7 @@ void recv_ishtp_cl_msg_dma(struct ishtp_device *dev, void *msg, ishtp_hbm_cl_flow_control_req(dev, cl); } else { - spin_unlock_irqrestore(&cl->free_list_spinlock, - flags); + spin_unlock(&cl->free_list_spinlock); } /* One more fragment in message (this is always last) */ @@ -1038,7 +1029,7 @@ void recv_ishtp_cl_msg_dma(struct ishtp_device *dev, void *msg, break; } - spin_unlock_irqrestore(&dev->read_list_spinlock, dev_flags); + spin_unlock_irqrestore(&dev->read_list_spinlock, flags); /* If it's nobody's message, just read and discard it */ if (!buffer) { dev_err(dev->devc, "Dropped Rx (DMA) msg - no request\n");