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In coda_lookup, add LK_RETRY to locking of child vnode. The previous 

code paniced if the first attempt to lock the vnode failed, and such
failures are not errors - just cause to wait.  gdt was regularly
hitting this panic.

Correct one of two identical panic messages.

Add XXX comments about

  ISDOTDOT locking rules not being followed

  questioning the practice of unlocking parent before locking child.
  (But, given that the vnode is referenced, it can't be deleted, so
  maybe this is fine.)

  Why is failured to unlock not a panic but failure to lock is?
This commit is contained in:
gdt 2006-01-12 14:57:06 +00:00
parent 403fb83166
commit 6fbdb2adf5
1 changed files with 10 additions and 7 deletions
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17
sys/coda/coda_vnops.c
View File

@ -6,7 +6,7 @@ mkdir
rmdir
symlink
*/
/* $NetBSD: coda_vnops.c,v 1.45 2005/12/11 12:19:50 christos Exp $ */
/* $NetBSD: coda_vnops.c,v 1.46 2006/01/12 14:57:06 gdt Exp $ */
/*
*
@ -54,7 +54,7 @@ symlink
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: coda_vnops.c,v 1.45 2005/12/11 12:19:50 christos Exp $");
__KERNEL_RCSID(0, "$NetBSD: coda_vnops.c,v 1.46 2006/01/12 14:57:06 gdt Exp $");
#include <sys/param.h>
#include <sys/systm.h>
@ -1006,7 +1006,12 @@ coda_lookup(void *v)
* we are ISLASTCN
*/
if (!error || (error == EJUSTRETURN)) {
/* XXX ISDOTDOT changes locking rules - not handled. */
if (!(cnp->cn_flags & LOCKPARENT) || !(cnp->cn_flags & ISLASTCN)) {
/*
* XXX Lock child before unlocking parent?
* XXX Why is it ok to fail to unlock, but a panic to fail to lock?
*/
if ((error = VOP_UNLOCK(dvp, 0))) {
return error;
}
@ -1016,8 +1021,7 @@ coda_lookup(void *v)
* lock it without bothering to check anything else.
*/
if (*ap->a_vpp) {
if ((error = vn_lock(*ap->a_vpp, LK_EXCLUSIVE))) {
printf("coda_lookup: ");
if ((error = vn_lock(*ap->a_vpp, LK_EXCLUSIVE|LK_RETRY))) {
panic("unlocked parent but couldn't lock child");
}
}
@ -1025,9 +1029,8 @@ coda_lookup(void *v)
/* The parent is locked, and may be the same as the child */
if (*ap->a_vpp && (*ap->a_vpp != dvp)) {
/* Different, go ahead and lock it. */
if ((error = vn_lock(*ap->a_vpp, LK_EXCLUSIVE))) {
printf("coda_lookup: ");
panic("unlocked parent but couldn't lock child");
if ((error = vn_lock(*ap->a_vpp, LK_EXCLUSIVE|LK_RETRY))) {
panic("kept parent locked but couldn't lock child");
}
}
}