[PATCH] PPC64 iSeries: replace semaphores with completions

This replaces some usages of sempahores on the stack with completions.

We think we have had at least one bug report that could be caused by the
inherent race in the semaphore usage.

diff --git a/arch/ppc64/kernel/mf.c b/arch/ppc64/kernel/mf.c
index dd30aaad9d8c1e7b2999560ea74897f4abde93fc..02a68b1165779bf60897fe71eee10b217a98c727 100644 (file)
--- a/arch/ppc64/kernel/mf.c
+++ b/arch/ppc64/kernel/mf.c
@@ -31,6 +31,7 @@
 #include <linux/init.h>
 #include <linux/mm.h>
 #include <linux/module.h>
+#include <linux/completion.h>
 #include <asm/iSeries/HvLpConfig.h>
 #include <linux/slab.h>
 #include <linux/delay.h>
@@ -81,7 +82,7 @@ struct VspCmdData {
 };
 
 struct VspRspData {
-       struct semaphore *sem;
+       struct completion com;
        struct VspCmdData *response;
 };
 
@@ -276,12 +277,11 @@ static int signal_vsp_instruction(struct VspCmdData *vspCmd)
        struct pending_event *ev = new_pending_event();
        int rc;
        struct VspRspData response;
-       DECLARE_MUTEX_LOCKED(Semaphore);
 
        if (ev == NULL)
                return -ENOMEM;
 
-       response.sem = &Semaphore;
+       init_completion(&response.com);
        response.response = vspCmd;
        ev->event.hp_lp_event.xSubtype = 6;
        ev->event.hp_lp_event.x.xSubtypeData =
@@ -297,7 +297,7 @@ static int signal_vsp_instruction(struct VspCmdData *vspCmd)
 
        rc = signal_event(ev);
        if (rc == 0)
-               down(&Semaphore);
+               wait_for_completion(&response.com);
        return rc;
 }
 
@@ -477,8 +477,7 @@ static void ackReceived(struct IoMFLpEvent *event)
                                if (rsp != NULL) {
                                        if (rsp->response != NULL)
                                                memcpy(rsp->response, &(event->data.vsp_cmd), sizeof(event->data.vsp_cmd));
-                                       if (rsp->sem != NULL)
-                                               up(rsp->sem);
+                                       complete(&rsp->com);
                                } else
                                        printk(KERN_ERR "mf.c: no rsp\n");
                                freeIt = 1;
@@ -919,7 +918,7 @@ int mf_setRtcTime(unsigned long time)
 }
 
 struct RtcTimeData {
-       struct semaphore *sem;
+       struct completion com;
        struct CeMsgData xCeMsg;
        int xRc;
 };
@@ -930,7 +929,7 @@ void getRtcTimeComplete(void * token, struct CeMsgData *ceMsg)
 
        memcpy(&(rtc->xCeMsg), ceMsg, sizeof(rtc->xCeMsg));
        rtc->xRc = 0;
-       up(rtc->sem);
+       complete(&rtc->com);
 }
 
 static unsigned long lastsec = 1;
@@ -978,17 +977,16 @@ int mf_getRtc(struct rtc_time *tm)
        struct CeMsgCompleteData ceComplete;
        struct RtcTimeData rtcData;
        int rc;
-       DECLARE_MUTEX_LOCKED(Semaphore);
 
        memset(&ceComplete, 0, sizeof(ceComplete));
        memset(&rtcData, 0, sizeof(rtcData));
-       rtcData.sem = &Semaphore;
+       init_completion(&rtcData.com);
        ceComplete.handler = &getRtcTimeComplete;
        ceComplete.token = (void *)&rtcData;
        rc = signal_ce_msg("\x00\x00\x00\x40\x00\x00\x00\x00\x00\x00\x00\x00",
                        &ceComplete);
        if (rc == 0) {
-               down(&Semaphore);
+               wait_for_completion(&rtcData.com);
 
                if (rtcData.xRc == 0) {
                        if ((rtcData.xCeMsg.ce_msg[2] == 0xa9) ||