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Switch context before doing some i/o operations that might block if

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context would be switched on return to user mode.  This fixes some
denial of service problems.
This commit is contained in:
Bruce Evans 1999-02-02 12:11:01 +00:00
parent ed0e926999
commit 8b6ca0359b
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=43529
1 changed files with 26 additions and 1 deletions
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27
sys/kern/kern_subr.c
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@ -36,7 +36,7 @@
* SUCH DAMAGE.
*
* @(#)kern_subr.c 8.3 (Berkeley) 1/21/94
* $Id: kern_subr.c,v 1.23 1999/01/08 17:31:10 eivind Exp $
* $Id: kern_subr.c,v 1.24 1999/01/10 01:58:24 eivind Exp $
*/
#include <sys/param.h>
@ -44,6 +44,7 @@
#include <sys/proc.h>
#include <sys/malloc.h>
#include <sys/lock.h>
#include <sys/resourcevar.h>
#include <sys/vnode.h>
#include <vm/vm.h>
@ -51,6 +52,10 @@
#include <vm/vm_page.h>
#include <vm/vm_map.h>
#include <machine/cpu.h>
static void uio_yield __P((void));
int
uiomove(cp, n, uio)
register caddr_t cp;
@ -81,6 +86,8 @@ uiomove(cp, n, uio)
case UIO_USERSPACE:
case UIO_USERISPACE:
if (resched_wanted())
uio_yield();
if (uio->uio_rw == UIO_READ)
error = copyout(cp, iov->iov_base, cnt);
else
@ -139,6 +146,8 @@ uiomoveco(cp, n, uio, obj)
case UIO_USERSPACE:
case UIO_USERISPACE:
if (resched_wanted())
uio_yield();
if (uio->uio_rw == UIO_READ) {
if (vfs_ioopt && ((cnt & PAGE_MASK) == 0) &&
((((intptr_t) iov->iov_base) & PAGE_MASK) == 0) &&
@ -214,6 +223,8 @@ uioread(n, uio, obj, nread)
cnt &= ~PAGE_MASK;
if (resched_wanted())
uio_yield();
error = vm_uiomove(&curproc->p_vmspace->vm_map, obj,
uio->uio_offset, cnt,
(vm_offset_t) iov->iov_base, &npagesmoved);
@ -389,3 +400,17 @@ phashinit(elements, type, nentries)
*nentries = hashsize;
return (hashtbl);
}
static void
uio_yield()
{
struct proc *p;
int s;
p = curproc;
s = splhigh();
setrunqueue(p);
p->p_stats->p_ru.ru_nivcsw++;
mi_switch();
splx(s);
}