[PATCH] tools/ocaml: Release the global lock before invoking block syscalls

[PATCH] tools/ocaml: Release the global lock before invoking block syscalls

[Yang Qian]

Functions related with event channel are parallelizable, so release global
lock before invoking C function which will finally call block syscalls.

Signed-off-by: Yang Qian <yang.qian@citrix.com>
---
 tools/ocaml/libs/eventchn/xeneventchn_stubs.c | 30 +++++++++++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)

diff --git a/tools/ocaml/libs/eventchn/xeneventchn_stubs.c b/tools/ocaml/libs/eventchn/xeneventchn_stubs.c
index 2b7984f..ba40078 100644
--- a/tools/ocaml/libs/eventchn/xeneventchn_stubs.c
+++ b/tools/ocaml/libs/eventchn/xeneventchn_stubs.c
@@ -32,6 +32,7 @@
 #include <caml/custom.h>
 #include <caml/callback.h>
 #include <caml/fail.h>
+#include <caml/signals.h>
 
 #define _H(__h) ((xenevtchn_handle *)(__h))
 
@@ -39,8 +40,12 @@ CAMLprim value stub_eventchn_init(void)
 {
 	CAMLparam0();
 	CAMLlocal1(result);
+	xenevtchn_handle *xce;
+
+	caml_enter_blocking_section();
+	xce = xenevtchn_open(NULL, 0);
+	caml_leave_blocking_section();
 
-	xenevtchn_handle *xce = xenevtchn_open(NULL, 0);
 	if (xce == NULL)
 		caml_failwith("open failed");
 
@@ -68,7 +73,10 @@ CAMLprim value stub_eventchn_notify(value xce, value port)
 	CAMLparam2(xce, port);
 	int rc;
 
+	caml_enter_blocking_section();
 	rc = xenevtchn_notify(_H(xce), Int_val(port));
+	caml_leave_blocking_section();
+
 	if (rc == -1)
 		caml_failwith("evtchn notify failed");
 
@@ -82,7 +90,10 @@ CAMLprim value stub_eventchn_bind_interdomain(value xce, value domid,
 	CAMLlocal1(port);
 	xenevtchn_port_or_error_t rc;
 
+	caml_enter_blocking_section();
 	rc = xenevtchn_bind_interdomain(_H(xce), Int_val(domid), Int_val(remote_port));
+	caml_leave_blocking_section();
+
 	if (rc == -1)
 		caml_failwith("evtchn bind_interdomain failed");
 	port = Val_int(rc);
@@ -96,7 +107,10 @@ CAMLprim value stub_eventchn_bind_virq(value xce, value virq_type)
 	CAMLlocal1(port);
 	xenevtchn_port_or_error_t rc;
 
+	caml_enter_blocking_section();
 	rc = xenevtchn_bind_virq(_H(xce), Int_val(virq_type));
+	caml_leave_blocking_section();
+
 	if (rc == -1)
 		caml_failwith("evtchn bind_virq failed");
 	port = Val_int(rc);
@@ -109,7 +123,10 @@ CAMLprim value stub_eventchn_unbind(value xce, value port)
 	CAMLparam2(xce, port);
 	int rc;
 
+	caml_enter_blocking_section();
 	rc = xenevtchn_unbind(_H(xce), Int_val(port));
+	caml_leave_blocking_section();
+
 	if (rc == -1)
 		caml_failwith("evtchn unbind failed");
 
@@ -122,7 +139,10 @@ CAMLprim value stub_eventchn_pending(value xce)
 	CAMLlocal1(result);
 	xenevtchn_port_or_error_t port;
 
+	caml_enter_blocking_section();
 	port = xenevtchn_pending(_H(xce));
+	caml_leave_blocking_section();
+
 	if (port == -1)
 		caml_failwith("evtchn pending failed");
 	result = Val_int(port);
@@ -134,9 +154,15 @@ CAMLprim value stub_eventchn_unmask(value xce, value _port)
 {
 	CAMLparam2(xce, _port);
 	evtchn_port_t port;
+	int rc;
 
 	port = Int_val(_port);
-	if (xenevtchn_unmask(_H(xce), port))
+
+	caml_enter_blocking_section();
+	rc = xenevtchn_unmask(_H(xce), port);
+	caml_leave_blocking_section();
+
+	if (rc)
 		caml_failwith("evtchn unmask failed");
 	CAMLreturn(Val_unit);
 }
-- 
2.9.5


_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

Re: [PATCH] tools/ocaml: Release the global lock before invoking block syscalls

[Christian Lindig]

> On 8 Oct 2018, at 04:10, Yang Qian <krizex@gmail.com> wrote:
> 
> Functions related with event channel are parallelizable, so release global
> lock before invoking C function which will finally call block syscalls.
> 
> Signed-off-by: Yang Qian <yang.qian@citrix.com>
> ---
> tools/ocaml/libs/eventchn/xeneventchn_stubs.c | 30 +++++++++++++++++++++++++--
> 1 file changed, 28 insertions(+), 2 deletions(-)

Acked-by: Christian Lindig <christian.lindig@citrix.com>

From an OCaml point of view this is looking good. But I would like to hear from developers understanding event channels that this is indeed safe to do.

— Christian


_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

Re: [PATCH] tools/ocaml: Release the global lock before invoking block syscalls

[Andrew Cooper]

On 08/10/18 08:58, Christian Lindig wrote:
>
>> On 8 Oct 2018, at 04:10, Yang Qian <krizex@gmail.com> wrote:
>>
>> Functions related with event channel are parallelizable, so release global
>> lock before invoking C function which will finally call block syscalls.
>>
>> Signed-off-by: Yang Qian <yang.qian@citrix.com>
>> ---
>> tools/ocaml/libs/eventchn/xeneventchn_stubs.c | 30 +++++++++++++++++++++++++--
>> 1 file changed, 28 insertions(+), 2 deletions(-)
> Acked-by: Christian Lindig <christian.lindig@citrix.com>
>
> From an OCaml point of view this is looking good. But I would like to hear from developers understanding event channels that this is indeed safe to do.

They all end up as ioctl()'s into the kernel, and from there some become
hypercalls into Xen.

Either way, this patch is fine.  Reviewed-by: Andrew Cooper
<andrew.cooper3@citrix.com>

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel