[PATCH, RFC] kill odd mm context pinning hack in frv

[PATCH, RFC] kill odd mm context pinning hack in frv

[Christoph Hellwig]

David, is that more than a debugging aid?   I'm trying to get rid of
tasklist_lock users and this one looks really suspicios..


Signed-off-by: Christoph Hellwig <hch@lst.de>

Index: linux-2.6/arch/frv/kernel/sysctl.c
===================================================================
--- linux-2.6.orig/arch/frv/kernel/sysctl.c	2005-08-11 16:45:53.000000000 +0200
+++ linux-2.6/arch/frv/kernel/sysctl.c	2005-08-11 19:17:24.000000000 +0200
@@ -117,69 +117,12 @@
 
 } /* end procctl_frv_cachemode() */
 
-/*****************************************************************************/
-/*
- * permit the mm_struct the nominated process is using have its MMU context ID pinned
- */
-#ifdef CONFIG_MMU
-static int procctl_frv_pin_cxnr(ctl_table *table, int write, struct file *filp,
-				void *buffer, size_t *lenp, loff_t *ppos)
-{
-	pid_t pid;
-	char buff[16], *p;
-	int len;
-
-	len = *lenp;
-
-	if (write) {
-		/* potential state change */
-		if (len <= 1 || len > sizeof(buff) - 1)
-			return -EINVAL;
-
-		if (copy_from_user(buff, buffer, len) != 0)
-			return -EFAULT;
-
-		if (buff[len - 1] == '\n')
-			buff[len - 1] = '\0';
-		else
-			buff[len] = '\0';
-
-		pid = simple_strtoul(buff, &p, 10);
-		if (*p)
-			return -EINVAL;
-
-		return cxn_pin_by_pid(pid);
-	}
-
-	/* read the currently pinned CXN */
-	if (filp->f_pos > 0) {
-		*lenp = 0;
-		return 0;
-	}
-
-	len = snprintf(buff, sizeof(buff), "%d\n", cxn_pinned);
-	if (len > *lenp)
-		len = *lenp;
-
-	if (copy_to_user(buffer, buff, len) != 0)
-		return -EFAULT;
-
-	*lenp = len;
-	filp->f_pos = len;
-	return 0;
-
-} /* end procctl_frv_pin_cxnr() */
-#endif
-
 /*
  * FR-V specific sysctls
  */
 static struct ctl_table frv_table[] =
 {
 	{ 1, "cache-mode",	NULL, 0, 0644, NULL, &procctl_frv_cachemode },
-#ifdef CONFIG_MMU
-	{ 2, "pin-cxnr",	NULL, 0, 0644, NULL, &procctl_frv_pin_cxnr },
-#endif
 	{ 0 }
 };
 
Index: linux-2.6/include/asm-frv/mmu.h
===================================================================
--- linux-2.6.orig/include/asm-frv/mmu.h	2005-08-11 16:46:04.000000000 +0200
+++ linux-2.6/include/asm-frv/mmu.h	2005-08-11 19:18:10.000000000 +0200
@@ -34,9 +34,4 @@
 
 } mm_context_t;
 
-#ifdef CONFIG_MMU
-extern int __nongpreldata cxn_pinned;
-extern int cxn_pin_by_pid(pid_t pid);
-#endif
-
 #endif /* _ASM_MMU_H */

Re: [PATCH, RFC] kill odd mm context pinning hack in frv

[David Howells]

Christoph Hellwig <hch@lst.de> wrote:

> David, is that more than a debugging aid?   I'm trying to get rid of
> tasklist_lock users and this one looks really suspicios..

Yes. The FR451 CPU (the only one with an MMU at the moment) has accounting and
profiling aids that are enabled by the context number set in the CXNR
register. This context number also selectively enables TLB entries on a per-mm
context basis.

So to profile a process you pin a context number to that process, and then the
profiling h/w is only active for that process.

David