From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S944951AbdE0BPz (ORCPT ); Fri, 26 May 2017 21:15:55 -0400 Received: from mga07.intel.com ([134.134.136.100]:23196 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S944953AbdEZU6V (ORCPT ); Fri, 26 May 2017 16:58:21 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.38,399,1491289200"; d="scan'208";a="1135171590" Message-ID: <1495832299.79527.3.camel@linux.intel.com> Subject: Re: [PATCH v2 2/5] HID: intel_ish-hid: clarify locking in client code From: Srinivas Pandruvada To: Arnd Bergmann , Jiri Kosina Cc: linux-input@vger.kernel.org, linux-kernel@vger.kernel.org Date: Fri, 26 May 2017 13:58:19 -0700 In-Reply-To: <20170518202144.3482304-3-arnd@arndb.de> References: <20170518202144.3482304-1-arnd@arndb.de> <20170518202144.3482304-3-arnd@arndb.de> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.20.5 (3.20.5-1.fc24) Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2017-05-18 at 22:21 +0200, Arnd Bergmann wrote: > 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 > --- >  drivers/hid/intel-ish-hid/ishtp/client.c | 43 +++++++++++++--------- > ---------- >  1 file changed, 17 insertions(+), 26 deletions(-) > > 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 @@ void recv_ishtp_cl_msg(struct ishtp_device *dev, >   * @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");