Author: kib
Date: Fri Jun 22 06:39:28 2012
New Revision: 237431
URL: http://svn.freebsd.org/changeset/base/237431
Log:
Enchance the shared page chunk allocator.
Do not rely on the busy state of the page from which we allocate the
chunk, to protect allocator state. Use statically allocated sx lock
instead.
Provide more flexible KPI. In particular, allow to allocate chunk
without providing initial data, and allow writes into existing
allocation. Allow to get an sf buf which temporary maps the chunk, to
allow sequential updates to shared page content without unmapping in
between.
Reviewed by: jhb
Tested by: flo
MFC after: 1 month
Modified:
head/sys/kern/kern_exec.c
head/sys/sys/sysent.h
Modified: head/sys/kern/kern_exec.c
==============================================================================
--- head/sys/kern/kern_exec.c Fri Jun 22 06:38:31 2012 (r237430)
+++ head/sys/kern/kern_exec.c Fri Jun 22 06:39:28 2012 (r237431)
@@ -1512,33 +1512,81 @@ exec_unregister(execsw_arg)
return (0);
}
+static struct sx shared_page_alloc_sx;
static vm_object_t shared_page_obj;
static int shared_page_free;
-int
-shared_page_fill(int size, int align, const char *data)
+struct sf_buf *
+shared_page_write_start(int base)
{
vm_page_t m;
struct sf_buf *s;
+
+ VM_OBJECT_LOCK(shared_page_obj);
+ m = vm_page_grab(shared_page_obj, OFF_TO_IDX(base), VM_ALLOC_RETRY);
+ VM_OBJECT_UNLOCK(shared_page_obj);
+ s = sf_buf_alloc(m, SFB_DEFAULT);
+ return (s);
+}
+
+void
+shared_page_write_end(struct sf_buf *sf)
+{
+ vm_page_t m;
+
+ m = sf_buf_page(sf);
+ sf_buf_free(sf);
+ VM_OBJECT_LOCK(shared_page_obj);
+ vm_page_wakeup(m);
+ VM_OBJECT_UNLOCK(shared_page_obj);
+}
+
+void
+shared_page_write(int base, int size, const void *data)
+{
+ struct sf_buf *sf;
vm_offset_t sk;
+
+ sf = shared_page_write_start(base);
+ sk = sf_buf_kva(sf);
+ bcopy(data, (void *)(sk + (base & PAGE_MASK)), size);
+ shared_page_write_end(sf);
+}
+
+static int
+shared_page_alloc_locked(int size, int align)
+{
int res;
- VM_OBJECT_LOCK(shared_page_obj);
- m = vm_page_grab(shared_page_obj, 0, VM_ALLOC_RETRY);
res = roundup(shared_page_free, align);
if (res + size >= IDX_TO_OFF(shared_page_obj->size))
res = -1;
- else {
- VM_OBJECT_UNLOCK(shared_page_obj);
- s = sf_buf_alloc(m, SFB_DEFAULT);
- sk = sf_buf_kva(s);
- bcopy(data, (void *)(sk + res), size);
+ else
shared_page_free = res + size;
- sf_buf_free(s);
- VM_OBJECT_LOCK(shared_page_obj);
- }
- vm_page_wakeup(m);
- VM_OBJECT_UNLOCK(shared_page_obj);
+ return (res);
+}
+
+int
+shared_page_alloc(int size, int align)
+{
+ int res;
+
+ sx_xlock(&shared_page_alloc_sx);
+ res = shared_page_alloc_locked(size, align);
+ sx_xunlock(&shared_page_alloc_sx);
+ return (res);
+}
+
+int
+shared_page_fill(int size, int align, const void *data)
+{
+ int res;
+
+ sx_xlock(&shared_page_alloc_sx);
+ res = shared_page_alloc_locked(size, align);
+ if (res != -1)
+ shared_page_write(res, size, data);
+ sx_xunlock(&shared_page_alloc_sx);
return (res);
}
@@ -1547,6 +1595,7 @@ shared_page_init(void *dummy __unused)
{
vm_page_t m;
+ sx_init(&shared_page_alloc_sx, "shpsx");
shared_page_obj = vm_pager_allocate(OBJT_PHYS, 0, PAGE_SIZE,
VM_PROT_DEFAULT, 0, NULL);
VM_OBJECT_LOCK(shared_page_obj);
Modified: head/sys/sys/sysent.h
==============================================================================
--- head/sys/sys/sysent.h Fri Jun 22 06:38:31 2012 (r237430)
+++ head/sys/sys/sysent.h Fri Jun 22 06:39:28 2012 (r237431)
@@ -256,8 +256,13 @@ int lkmressys(struct thread *, struct no
int syscall_thread_enter(struct thread *td, struct sysent *se);
void syscall_thread_exit(struct thread *td, struct sysent *se);
-int shared_page_fill(int size, int align, const char *data);
+struct sf_buf;
+int shared_page_alloc(int size, int align);
+int shared_page_fill(int size, int align, const void *data);
+void shared_page_write(int base, int size, const void *data);
void exec_sysvec_init(void *param);
+struct sf_buf *shared_page_write_start(int base);
+void shared_page_write_end(struct sf_buf *sf);
#define INIT_SYSENTVEC(name, sv) \
SYSINIT(name, SI_SUB_EXEC, SI_ORDER_ANY, \
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