[PATCH] PPC64 iSeries: replace semaphores with completions

[Stephen Rothwell]

Hi Linus,

This patch 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.

Please apply.

--
Cheers,
Stephen Rothwell                    sfr at canb.auug.org.au
http://www.canb.auug.org.au/~sfr/
-------------- next part --------------
diff -ruN ppc64-linux-2.5/arch/ppc64/kernel/mf.c ppc64-linux-2.5.mf.1/arch/ppc64/kernel/mf.c
--- ppc64-linux-2.5/arch/ppc64/kernel/mf.c	2004-04-02 13:29:11.000000000 +1000
+++ ppc64-linux-2.5.mf.1/arch/ppc64/kernel/mf.c	2004-05-06 16:52:22.000000000 +1000
@@ -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 VspRspData {
-	struct semaphore *sem;
+	struct completion com;
 	struct VspCmdData *response;
 };

@@ -276,12 +277,11 @@
 	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 @@

 	rc = signal_event(ev);
 	if (rc == 0)
-		down(&Semaphore);
+		wait_for_completion(&response.com);
 	return rc;
 }

@@ -477,8 +477,7 @@
 				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 @@
 }

 struct RtcTimeData {
-	struct semaphore *sem;
+	struct completion com;
 	struct CeMsgData xCeMsg;
 	int xRc;
 };
@@ -930,7 +929,7 @@

 	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 @@
 	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) ||