[PATCH] USB Gadget: file_storage: remove "volatile" declarations

This patch (as612) removes the "volatile" declarations from the
file-storage gadget.  It turns out that they aren't needed for anything
much; adding a few memory barriers does a sufficient job.

The patch also removes a wait_queue.  Not much point having a queue when
only one task is ever going to be on it!

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 38 insertions, 21 deletions

diff --git a/drivers/usb/gadget/file_storage.c b/drivers/usb/gadget/file_storage.c
index f6c49b717d3f..0cea9782d7d4 100644
--- a/drivers/usb/gadget/file_storage.c
+++ b/drivers/usb/gadget/file_storage.c
@@ -239,7 +239,6 @@
 #include <linux/string.h>
 #include <linux/suspend.h>
 #include <linux/utsname.h>
-#include <linux/wait.h>
 
 #include <linux/usb_ch9.h>
 #include <linux/usb_gadget.h>
@@ -251,7 +250,7 @@
 
 #define DRIVER_DESC             "File-backed Storage Gadget"
 #define DRIVER_NAME             "g_file_storage"
-#define DRIVER_VERSION          "20 October 2004"
+#define DRIVER_VERSION          "28 November 2005"
 
 static const char longname[] = DRIVER_DESC;
 static const char shortname[] = DRIVER_NAME;
@@ -588,7 +587,7 @@ enum fsg_buffer_state {
 struct fsg_buffhd {
         void                            *buf;
         dma_addr_t                      dma;
-        volatile enum fsg_buffer_state  state;
+        enum fsg_buffer_state           state;
         struct fsg_buffhd               *next;
 
         /* The NetChip 2280 is faster, and handles some protocol faults
@@ -597,9 +596,9 @@ struct fsg_buffhd {
         unsigned int                    bulk_out_intended_length;
 
         struct usb_request              *inreq;
-        volatile int                    inreq_busy;
+        int                             inreq_busy;
         struct usb_request              *outreq;
-        volatile int                    outreq_busy;
+        int                             outreq_busy;
 };
 
 enum fsg_state {
@@ -637,11 +636,11 @@ struct fsg_dev {
 
         struct usb_ep           *ep0;           // Handy copy of gadget->ep0
         struct usb_request      *ep0req;        // For control responses
-        volatile unsigned int   ep0_req_tag;
+        unsigned int            ep0_req_tag;
         const char              *ep0req_name;
 
         struct usb_request      *intreq;        // For interrupt responses
-        volatile int            intreq_busy;
+        int                     intreq_busy;
         struct fsg_buffhd       *intr_buffhd;
 
         unsigned int            bulk_out_maxpacket;
@@ -671,7 +670,6 @@ struct fsg_dev {
         struct fsg_buffhd       *next_buffhd_to_drain;
         struct fsg_buffhd       buffhds[NUM_BUFFERS];
 
-        wait_queue_head_t       thread_wqh;
         int                     thread_wakeup_needed;
         struct completion       thread_notifier;
         struct task_struct      *thread_task;
@@ -1076,11 +1074,13 @@ static int populate_config_buf(struct usb_gadget *gadget,
 
 /* These routines may be called in process context or in_irq */
 
+/* Caller must hold fsg->lock */
 static void wakeup_thread(struct fsg_dev *fsg)
 {
         /* Tell the main thread that something has happened */
         fsg->thread_wakeup_needed = 1;
-        wake_up_all(&fsg->thread_wqh);
+        if (fsg->thread_task)
+                wake_up_process(fsg->thread_task);
 }
 
 
@@ -1167,11 +1167,12 @@ static void bulk_in_complete(struct usb_ep *ep, struct usb_request *req)
                 usb_ep_fifo_flush(ep);
 
         /* Hold the lock while we update the request and buffer states */
+        smp_wmb();
         spin_lock(&fsg->lock);
         bh->inreq_busy = 0;
         bh->state = BUF_STATE_EMPTY;
-        spin_unlock(&fsg->lock);
         wakeup_thread(fsg);
+        spin_unlock(&fsg->lock);
 }
 
 static void bulk_out_complete(struct usb_ep *ep, struct usb_request *req)
@@ -1188,11 +1189,12 @@ static void bulk_out_complete(struct usb_ep *ep, struct usb_request *req)
                 usb_ep_fifo_flush(ep);
 
         /* Hold the lock while we update the request and buffer states */
+        smp_wmb();
         spin_lock(&fsg->lock);
         bh->outreq_busy = 0;
         bh->state = BUF_STATE_FULL;
-        spin_unlock(&fsg->lock);
         wakeup_thread(fsg);
+        spin_unlock(&fsg->lock);
 }
 
 
@@ -1209,11 +1211,12 @@ static void intr_in_complete(struct usb_ep *ep, struct usb_request *req)
                 usb_ep_fifo_flush(ep);
 
         /* Hold the lock while we update the request and buffer states */
+        smp_wmb();
         spin_lock(&fsg->lock);
         fsg->intreq_busy = 0;
         bh->state = BUF_STATE_EMPTY;
-        spin_unlock(&fsg->lock);
         wakeup_thread(fsg);
+        spin_unlock(&fsg->lock);
 }
 
 #else
@@ -1264,8 +1267,8 @@ static void received_cbi_adsc(struct fsg_dev *fsg, struct fsg_buffhd *bh)
         fsg->cbbuf_cmnd_size = req->actual;
         memcpy(fsg->cbbuf_cmnd, req->buf, fsg->cbbuf_cmnd_size);
 
-        spin_unlock(&fsg->lock);
         wakeup_thread(fsg);
+        spin_unlock(&fsg->lock);
 }
 
 #else
@@ -1517,8 +1520,8 @@ static int fsg_setup(struct usb_gadget *gadget,
 
 /* Use this for bulk or interrupt transfers, not ep0 */
 static void start_transfer(struct fsg_dev *fsg, struct usb_ep *ep,
-                struct usb_request *req, volatile int *pbusy,
-                volatile enum fsg_buffer_state *state)
+                struct usb_request *req, int *pbusy,
+                enum fsg_buffer_state *state)
 {
         int     rc;
 
@@ -1526,8 +1529,11 @@ static void start_transfer(struct fsg_dev *fsg, struct usb_ep *ep,
                 dump_msg(fsg, "bulk-in", req->buf, req->length);
         else if (ep == fsg->intr_in)
                 dump_msg(fsg, "intr-in", req->buf, req->length);
+
+        spin_lock_irq(&fsg->lock);
         *pbusy = 1;
         *state = BUF_STATE_BUSY;
+        spin_unlock_irq(&fsg->lock);
         rc = usb_ep_queue(ep, req, GFP_KERNEL);
         if (rc != 0) {
                 *pbusy = 0;
@@ -1547,14 +1553,23 @@ static void start_transfer(struct fsg_dev *fsg, struct usb_ep *ep,
 
 static int sleep_thread(struct fsg_dev *fsg)
 {
-        int     rc;
+        int     rc = 0;
 
         /* Wait until a signal arrives or we are woken up */
-        rc = wait_event_interruptible(fsg->thread_wqh,
-                        fsg->thread_wakeup_needed);
+        for (;;) {
+                try_to_freeze();
+                set_current_state(TASK_INTERRUPTIBLE);
+                if (signal_pending(current)) {
+                        rc = -EINTR;
+                        break;
+                }
+                if (fsg->thread_wakeup_needed)
+                        break;
+                schedule();
+        }
+        __set_current_state(TASK_RUNNING);
         fsg->thread_wakeup_needed = 0;
-        try_to_freeze();
-        return (rc ? -EINTR : 0);
+        return rc;
 }
 
 
@@ -1791,6 +1806,7 @@ static int do_write(struct fsg_dev *fsg)
                 if (bh->state == BUF_STATE_EMPTY && !get_some_more)
                         break;                  // We stopped early
                 if (bh->state == BUF_STATE_FULL) {
+                        smp_rmb();
                         fsg->next_buffhd_to_drain = bh->next;
                         bh->state = BUF_STATE_EMPTY;
 
@@ -2359,6 +2375,7 @@ static int throw_away_data(struct fsg_dev *fsg)
 
                 /* Throw away the data in a filled buffer */
                 if (bh->state == BUF_STATE_FULL) {
+                        smp_rmb();
                         bh->state = BUF_STATE_EMPTY;
                         fsg->next_buffhd_to_drain = bh->next;
 
@@ -3024,6 +3041,7 @@ static int get_next_command(struct fsg_dev *fsg)
                         if ((rc = sleep_thread(fsg)) != 0)
                                 return rc;
                         }
+                smp_rmb();
                 rc = received_cbw(fsg, bh);
                 bh->state = BUF_STATE_EMPTY;
 
@@ -4072,7 +4090,6 @@ static int __init fsg_alloc(void)
         spin_lock_init(&fsg->lock);
         init_rwsem(&fsg->filesem);
         kref_init(&fsg->ref);
-        init_waitqueue_head(&fsg->thread_wqh);
         init_completion(&fsg->thread_notifier);
 
         the_fsg = fsg;