Re: [Xen-devel] [PATCH v6 08/12] libxl: ocaml: drop the ocaml heap lock before calling into libxl

[Dave Scott <Dave.Scott@xxxxxxxxxx>]

Thanks, the whole series looks good to me...

Acked-by: David Scott <dave.scott@xxxxxxxxxxxxx>

> -----Original Message-----
> From: Rob Hoes [mailto:rob.hoes@xxxxxxxxxx]
> Sent: 26 November 2013 11:15 PM
> To: xen-devel@xxxxxxxxxxxxx
> Cc: Ian Campbell; Ian Jackson; Dave Scott; Rob Hoes; Ian Jackson
> Subject: [PATCH v6 08/12] libxl: ocaml: drop the ocaml heap lock before
> calling into libxl
> 
> Ocaml has a heap lock which must be held whenever ocaml code is running.
> Ocaml usually drops this lock when it enters a potentially blocking low-level
> function, such as writing to a file. Libxl has its own lock, which it may 
> acquire
> when being called.
> 
> Things get interesting when libxl calls back into ocaml code. There is a risk
> of ending up in a deadlock when a thread holds both locks at the same time,
> then temporarily drop the ocaml lock, while another thread calls another
> libxl function.
> 
> To avoid deadlocks, we drop the ocaml heap lock before entering libxl, and
> reacquire it in callbacks to ocaml. This way, the ocaml heap lock is never
> held together with the libxl lock, except in osevent registration callbacks,
> and xentoollog callbacks. If we guarantee to not call any libxl functions
> inside those callbacks, we can avoid deadlocks.
> 
> This patch handle the dropping and reacquiring of the ocaml heap lock by
> the caml_enter_blocking_section and caml_leave_blocking_section
> functions, and related macros. We are also careful to not call any functions
> that access the ocaml heap while the ocaml heap lock is dropped. This often
> involves copying ocaml values to C before dropping the ocaml lock.
> 
> Signed-off-by: Rob Hoes <rob.hoes@xxxxxxxxxx>
> CC: Ian Campbell <ian.campbell@xxxxxxxxxx>
> CC: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> CC: Dave Scott <dave.scott@xxxxxxxxxxxxx>
> ---
>  tools/ocaml/libs/xentoollog/Makefile           |    3 +
>  tools/ocaml/libs/xentoollog/xentoollog_stubs.c |   13 +-
>  tools/ocaml/libs/xl/Makefile                   |    5 +-
>  tools/ocaml/libs/xl/xenlight_stubs.c           |  265 
> +++++++++++++++++++-----
>  4 files changed, 229 insertions(+), 57 deletions(-)
> 
> diff --git a/tools/ocaml/libs/xentoollog/Makefile
> b/tools/ocaml/libs/xentoollog/Makefile
> index e535ba5..471b428 100644
> --- a/tools/ocaml/libs/xentoollog/Makefile
> +++ b/tools/ocaml/libs/xentoollog/Makefile
> @@ -2,6 +2,9 @@ TOPLEVEL=$(CURDIR)/../..
>  XEN_ROOT=$(TOPLEVEL)/../..
>  include $(TOPLEVEL)/common.make
> 
> +# allow mixed declarations and code
> +CFLAGS += -Wno-declaration-after-statement
> +
>  CFLAGS += $(CFLAGS_libxenctrl) $(CFLAGS_libxenguest)  OCAMLINCLUDE +=
> 
> diff --git a/tools/ocaml/libs/xentoollog/xentoollog_stubs.c
> b/tools/ocaml/libs/xentoollog/xentoollog_stubs.c
> index 3b2f91b..daf48fe 100644
> --- a/tools/ocaml/libs/xentoollog/xentoollog_stubs.c
> +++ b/tools/ocaml/libs/xentoollog/xentoollog_stubs.c
> @@ -31,6 +31,11 @@
> 
>  #include "caml_xentoollog.h"
> 
> +/* The following is equal to the CAMLreturn macro, but without the
> +return */ #define CAMLdone do{ \ caml_local_roots = caml__frame; \
> +}while (0)
> +
>  #define XTL ((xentoollog_logger *) Xtl_val(handle))
> 
>  static char * dup_String_val(value s)
> @@ -81,6 +86,7 @@ static void stub_xtl_ocaml_vmessage(struct
> xentoollog_logger *logger,
>       const char *format,
>       va_list al)
>  {
> +     caml_leave_blocking_section();
>       CAMLparam0();
>       CAMLlocalN(args, 4);
>       struct caml_xtl *xtl = (struct caml_xtl*)logger; @@ -103,7 +109,8 @@
> static void stub_xtl_ocaml_vmessage(struct xentoollog_logger *logger,
>       free(msg);
> 
>       caml_callbackN(*func, 4, args);
> -     CAMLreturn0;
> +     CAMLdone;
> +     caml_enter_blocking_section();
>  }
> 
>  static void stub_xtl_ocaml_progress(struct xentoollog_logger *logger, @@ -
> 111,6 +118,7 @@ static void stub_xtl_ocaml_progress(struct
> xentoollog_logger *logger,
>       const char *doing_what /* no \r,\n */,
>       int percent, unsigned long done, unsigned long total)  {
> +     caml_leave_blocking_section();
>       CAMLparam0();
>       CAMLlocalN(args, 5);
>       struct caml_xtl *xtl = (struct caml_xtl*)logger; @@ -129,7 +137,8 @@
> static void stub_xtl_ocaml_progress(struct xentoollog_logger *logger,
>       args[4] = caml_copy_int64(total);
> 
>       caml_callbackN(*func, 5, args);
> -     CAMLreturn0;
> +     CAMLdone;
> +     caml_enter_blocking_section();
>  }
> 
>  static void xtl_destroy(struct xentoollog_logger *logger) diff --git
> a/tools/ocaml/libs/xl/Makefile b/tools/ocaml/libs/xl/Makefile index
> 0408cc2..61eb44c 100644
> --- a/tools/ocaml/libs/xl/Makefile
> +++ b/tools/ocaml/libs/xl/Makefile
> @@ -2,8 +2,9 @@ TOPLEVEL=$(CURDIR)/../..
>  XEN_ROOT=$(TOPLEVEL)/../..
>  include $(TOPLEVEL)/common.make
> 
> -# ignore unused generated functions
> -CFLAGS += -Wno-unused
> +# ignore unused generated functions and allow mixed declarations and
> +code CFLAGS += -Wno-unused -Wno-declaration-after-statement
> +
>  CFLAGS += $(CFLAGS_libxenlight)
>  CFLAGS += -I ../xentoollog
> 
> diff --git a/tools/ocaml/libs/xl/xenlight_stubs.c
> b/tools/ocaml/libs/xl/xenlight_stubs.c
> index 88cca20..50b0325 100644
> --- a/tools/ocaml/libs/xl/xenlight_stubs.c
> +++ b/tools/ocaml/libs/xl/xenlight_stubs.c
> @@ -34,6 +34,11 @@
> 
>  #include "caml_xentoollog.h"
> 
> +/* The following is equal to the CAMLreturn macro, but without the
> +return */ #define CAMLdone do{ \ caml_local_roots = caml__frame; \
> +}while (0)
> +
>  #define Ctx_val(x)(*((libxl_ctx **) Data_custom_val(x)))  #define CTX
> ((libxl_ctx *) Ctx_val(ctx))
> 
> @@ -374,6 +379,7 @@ static char *String_option_val(value v)
> 
>  void async_callback(libxl_ctx *ctx, int rc, void *for_callback)  {
> +     caml_leave_blocking_section();
>       CAMLparam0();
>       CAMLlocal1(error);
>       int *task = (int *) for_callback;
> @@ -390,19 +396,22 @@ void async_callback(libxl_ctx *ctx, int rc, void
> *for_callback)
>               error = Val_some(Val_error(rc));
> 
>       caml_callback2(*func, error, (value) for_callback);
> +     CAMLdone;
> +     caml_enter_blocking_section();
>  }
> 
> -static libxl_asyncop_how *aohow_val(value async, libxl_asyncop_how
> *ao_how)
> +static libxl_asyncop_how *aohow_val(value async)
>  {
>       CAMLparam1(async);
> +     libxl_asyncop_how *ao_how = NULL;
> 
>       if (async != Val_none) {
> +             libxl_asyncop_how *ao_how = malloc(sizeof(*ao_how));
>               ao_how->callback = async_callback;
>               ao_how->u.for_callback = (void *) Some_val(async);
> -             CAMLreturnT(libxl_asyncop_how *, ao_how);
>       }
> -     else
> -             CAMLreturnT(libxl_asyncop_how *, NULL);
> +
> +     CAMLreturnT(libxl_asyncop_how *, ao_how);
>  }
> 
>  value stub_libxl_domain_create_new(value ctx, value domain_config,
> value async, value unit) @@ -411,7 +420,7 @@ value
> stub_libxl_domain_create_new(value ctx, value domain_config, value async,
>       int ret;
>       libxl_domain_config c_dconfig;
>       uint32_t c_domid;
> -     libxl_asyncop_how ao_how;
> +     libxl_asyncop_how *ao_how;
> 
>       libxl_domain_config_init(&c_dconfig);
>       ret = domain_config_val(CTX, &c_dconfig, domain_config); @@ -
> 420,9 +429,14 @@ value stub_libxl_domain_create_new(value ctx, value
> domain_config, value async,
>               failwith_xl(ret, "domain_create_new");
>       }
> 
> -     ret = libxl_domain_create_new(CTX, &c_dconfig, &c_domid,
> -             aohow_val(async, &ao_how), NULL);
> +     ao_how = aohow_val(async);
> 
> +     caml_enter_blocking_section();
> +     ret = libxl_domain_create_new(CTX, &c_dconfig, &c_domid, ao_how,
> NULL);
> +     caml_leave_blocking_section();
> +
> +     if (ao_how)
> +             free(ao_how);
>       libxl_domain_config_dispose(&c_dconfig);
> 
>       if (ret != 0)
> @@ -439,7 +453,8 @@ value stub_libxl_domain_create_restore(value ctx,
> value domain_config, value par
>       libxl_domain_config c_dconfig;
>       libxl_domain_restore_params c_params;
>       uint32_t c_domid;
> -     libxl_asyncop_how ao_how;
> +     libxl_asyncop_how *ao_how;
> +     int restore_fd;
> 
>       libxl_domain_config_init(&c_dconfig);
>       ret = domain_config_val(CTX, &c_dconfig, domain_config); @@ -
> 455,9 +470,16 @@ value stub_libxl_domain_create_restore(value ctx, value
> domain_config, value par
>               failwith_xl(ret, "domain_create_restore");
>       }
> 
> -     ret = libxl_domain_create_restore(CTX, &c_dconfig, &c_domid,
> Int_val(Field(params, 0)),
> -             &c_params, aohow_val(async, &ao_how), NULL);
> +     ao_how = aohow_val(async);
> +     restore_fd = Int_val(Field(params, 0));
> +
> +     caml_enter_blocking_section();
> +     ret = libxl_domain_create_restore(CTX, &c_dconfig, &c_domid,
> restore_fd,
> +             &c_params, ao_how, NULL);
> +     caml_leave_blocking_section();
> 
> +     if (ao_how)
> +             free(ao_how);
>       libxl_domain_config_dispose(&c_dconfig);
>       libxl_domain_restore_params_dispose(&c_params);
> 
> @@ -471,8 +493,12 @@ value stub_libxl_domain_shutdown(value ctx, value
> domid)  {
>       CAMLparam2(ctx, domid);
>       int ret;
> +     uint32_t c_domid = Int_val(domid);
> +
> +     caml_enter_blocking_section();
> +     ret = libxl_domain_shutdown(CTX, c_domid);
> +     caml_leave_blocking_section();
> 
> -     ret = libxl_domain_shutdown(CTX, Int_val(domid));
>       if (ret != 0)
>               failwith_xl(ret, "domain_shutdown");
> 
> @@ -483,8 +509,12 @@ value stub_libxl_domain_reboot(value ctx, value
> domid)  {
>       CAMLparam2(ctx, domid);
>       int ret;
> +     uint32_t c_domid = Int_val(domid);
> +
> +     caml_enter_blocking_section();
> +     ret = libxl_domain_reboot(CTX, c_domid);
> +     caml_leave_blocking_section();
> 
> -     ret = libxl_domain_reboot(CTX, Int_val(domid));
>       if (ret != 0)
>               failwith_xl(ret, "domain_reboot");
> 
> @@ -495,9 +525,16 @@ value stub_libxl_domain_destroy(value ctx, value
> domid, value async, value unit)  {
>       CAMLparam4(ctx, domid, async, unit);
>       int ret;
> -     libxl_asyncop_how ao_how;
> +     uint32_t c_domid = Int_val(domid);
> +     libxl_asyncop_how *ao_how = aohow_val(async);
> +
> +     caml_enter_blocking_section();
> +     ret = libxl_domain_destroy(CTX, c_domid, ao_how);
> +     caml_leave_blocking_section();
> +
> +     if (ao_how)
> +             free(ao_how);
> 
> -     ret = libxl_domain_destroy(CTX, Int_val(domid), aohow_val(async,
> &ao_how));
>       if (ret != 0)
>               failwith_xl(ret, "domain_destroy");
> 
> @@ -508,10 +545,17 @@ value stub_libxl_domain_suspend(value ctx, value
> domid, value fd, value async, v  {
>       CAMLparam5(ctx, domid, fd, async, unit);
>       int ret;
> -     libxl_asyncop_how ao_how;
> +     uint32_t c_domid = Int_val(domid);
> +     int c_fd = Int_val(fd);
> +     libxl_asyncop_how *ao_how = aohow_val(async);
> +
> +     caml_enter_blocking_section();
> +     ret = libxl_domain_suspend(CTX, c_domid, c_fd, 0, ao_how);
> +     caml_leave_blocking_section();
> +
> +     if (ao_how)
> +             free(ao_how);
> 
> -     ret = libxl_domain_suspend(CTX, Int_val(domid), Int_val(fd), 0,
> -             aohow_val(async, &ao_how));
>       if (ret != 0)
>               failwith_xl(ret, "domain_suspend");
> 
> @@ -522,8 +566,12 @@ value stub_libxl_domain_pause(value ctx, value
> domid)  {
>       CAMLparam2(ctx, domid);
>       int ret;
> +     uint32_t c_domid = Int_val(domid);
> +
> +     caml_enter_blocking_section();
> +     ret = libxl_domain_pause(CTX, c_domid);
> +     caml_leave_blocking_section();
> 
> -     ret = libxl_domain_pause(CTX, Int_val(domid));
>       if (ret != 0)
>               failwith_xl(ret, "domain_pause");
> 
> @@ -534,8 +582,12 @@ value stub_libxl_domain_unpause(value ctx, value
> domid)  {
>       CAMLparam2(ctx, domid);
>       int ret;
> +     uint32_t c_domid = Int_val(domid);
> +
> +     caml_enter_blocking_section();
> +     ret = libxl_domain_unpause(CTX, c_domid);
> +     caml_leave_blocking_section();
> 
> -     ret = libxl_domain_unpause(CTX, Int_val(domid));
>       if (ret != 0)
>               failwith_xl(ret, "domain_unpause");
> 
> @@ -552,13 +604,17 @@ value stub_xl_device_##type##_##op(value ctx,
> value info, value domid,      \
>       CAMLparam5(ctx, info, domid, async, unit);                      \
>       libxl_device_##type c_info;                                     \
>       int ret, marker_var;                                            \
> -     libxl_asyncop_how ao_how;                                       \
> +     uint32_t c_domid = Int_val(domid);
>       \
> +     libxl_asyncop_how *ao_how = aohow_val(async);
>       \
>                                                                       \
>       device_##type##_val(CTX, &c_info, info);                        \
>                                                                       \
> -     ret = libxl_##fn##_##op(CTX, Int_val(domid), &c_info,           \
> -             aohow_val(async, &ao_how));                             \
> +     caml_enter_blocking_section();
>       \
> +     ret = libxl_##fn##_##op(CTX, c_domid, &c_info, ao_how);
>       \
> +     caml_leave_blocking_section();
>       \
>                                                                       \
> +     if (ao_how)                                                     \
> +             free(ao_how);                                           \
>       libxl_device_##type##_dispose(&c_info);
>       \
>                                                                       \
>       if (ret != 0)                                                   \
> @@ -584,9 +640,16 @@ value stub_xl_device_nic_of_devid(value ctx, value
> domid, value devid)
>       CAMLparam3(ctx, domid, devid);
>       CAMLlocal1(nic);
>       libxl_device_nic c_nic;
> -     libxl_devid_to_device_nic(CTX, Int_val(domid), Int_val(devid),
> &c_nic);
> +     uint32_t c_domid = Int_val(domid);
> +     int c_devid = Int_val(devid);
> +
> +     caml_enter_blocking_section();
> +     libxl_devid_to_device_nic(CTX, c_domid, c_devid, &c_nic);
> +     caml_leave_blocking_section();
> +
>       nic = Val_device_nic(&c_nic);
>       libxl_device_nic_dispose(&c_nic);
> +
>       CAMLreturn(nic);
>  }
> 
> @@ -596,11 +659,12 @@ value stub_xl_device_nic_list(value ctx, value
> domid)
>       CAMLlocal2(list, temp);
>       libxl_device_nic *c_list;
>       int i, nb;
> -     uint32_t c_domid;
> -
> -     c_domid = Int_val(domid);
> +     uint32_t c_domid = Int_val(domid);
> 
> +     caml_enter_blocking_section();
>       c_list = libxl_device_nic_list(CTX, c_domid, &nb);
> +     caml_leave_blocking_section();
> +
>       if (!c_list)
>               failwith_xl(ERROR_FAIL, "nic_list");
> 
> @@ -624,11 +688,12 @@ value stub_xl_device_disk_list(value ctx, value
> domid)
>       CAMLlocal2(list, temp);
>       libxl_device_disk *c_list;
>       int i, nb;
> -     uint32_t c_domid;
> -
> -     c_domid = Int_val(domid);
> +     uint32_t c_domid = Int_val(domid);
> 
> +     caml_enter_blocking_section();
>       c_list = libxl_device_disk_list(CTX, c_domid, &nb);
> +     caml_leave_blocking_section();
> +
>       if (!c_list)
>               failwith_xl(ERROR_FAIL, "disk_list");
> 
> @@ -651,9 +716,19 @@ value stub_xl_device_disk_of_vdev(value ctx, value
> domid, value vdev)
>       CAMLparam3(ctx, domid, vdev);
>       CAMLlocal1(disk);
>       libxl_device_disk c_disk;
> -     libxl_vdev_to_device_disk(CTX, Int_val(domid), String_val(vdev),
> &c_disk);
> +     char *c_vdev;
> +     uint32_t c_domid = Int_val(domid);
> +
> +     c_vdev = strdup(String_val(vdev));
> +
> +     caml_enter_blocking_section();
> +     libxl_vdev_to_device_disk(CTX, c_domid, c_vdev, &c_disk);
> +     caml_leave_blocking_section();
> +
>       disk = Val_device_disk(&c_disk);
>       libxl_device_disk_dispose(&c_disk);
> +     free(c_vdev);
> +
>       CAMLreturn(disk);
>  }
> 
> @@ -663,11 +738,12 @@ value stub_xl_device_pci_list(value ctx, value
> domid)
>       CAMLlocal2(list, temp);
>       libxl_device_pci *c_list;
>       int i, nb;
> -     uint32_t c_domid;
> -
> -     c_domid = Int_val(domid);
> +     uint32_t c_domid = Int_val(domid);
> 
> +     caml_enter_blocking_section();
>       c_list = libxl_device_pci_list(CTX, c_domid, &nb);
> +     caml_leave_blocking_section();
> +
>       if (!c_list)
>               failwith_xl(ERROR_FAIL, "pci_list");
> 
> @@ -690,10 +766,13 @@ value stub_xl_device_pci_assignable_add(value
> ctx, value info, value rebind)
>       CAMLparam3(ctx, info, rebind);
>       libxl_device_pci c_info;
>       int ret, marker_var;
> +     int c_rebind = (int) Bool_val(rebind);
> 
>       device_pci_val(CTX, &c_info, info);
> 
> -     ret = libxl_device_pci_assignable_add(CTX, &c_info, (int)
> Bool_val(rebind));
> +     caml_enter_blocking_section();
> +     ret = libxl_device_pci_assignable_add(CTX, &c_info, c_rebind);
> +     caml_leave_blocking_section();
> 
>       libxl_device_pci_dispose(&c_info);
> 
> @@ -708,10 +787,13 @@ value
> stub_xl_device_pci_assignable_remove(value ctx, value info, value rebind)
>       CAMLparam3(ctx, info, rebind);
>       libxl_device_pci c_info;
>       int ret, marker_var;
> +     int c_rebind = (int) Bool_val(rebind);
> 
>       device_pci_val(CTX, &c_info, info);
> 
> -     ret = libxl_device_pci_assignable_remove(CTX, &c_info, (int)
> Bool_val(rebind));
> +     caml_enter_blocking_section();
> +     ret = libxl_device_pci_assignable_remove(CTX, &c_info, c_rebind);
> +     caml_leave_blocking_section();
> 
>       libxl_device_pci_dispose(&c_info);
> 
> @@ -729,7 +811,10 @@ value stub_xl_device_pci_assignable_list(value ctx)
>       int i, nb;
>       uint32_t c_domid;
> 
> +     caml_enter_blocking_section();
>       c_list = libxl_device_pci_assignable_list(CTX, &nb);
> +     caml_leave_blocking_section();
> +
>       if (!c_list)
>               failwith_xl(ERROR_FAIL, "pci_assignable_list");
> 
> @@ -754,7 +839,9 @@ value stub_xl_physinfo_get(value ctx)
>       libxl_physinfo c_physinfo;
>       int ret;
> 
> +     caml_enter_blocking_section();
>       ret = libxl_get_physinfo(CTX, &c_physinfo);
> +     caml_leave_blocking_section();
> 
>       if (ret != 0)
>               failwith_xl(ret, "get_physinfo");
> @@ -773,7 +860,9 @@ value stub_xl_cputopology_get(value ctx)
>       libxl_cputopology *c_topology;
>       int i, nr;
> 
> +     caml_enter_blocking_section();
>       c_topology = libxl_get_cpu_topology(CTX, &nr);
> +     caml_leave_blocking_section();
> 
>       if (!c_topology)
>               failwith_xl(ERROR_FAIL, "get_cpu_topologyinfo"); @@ -
> 801,7 +890,10 @@ value stub_xl_dominfo_list(value ctx)
>       libxl_dominfo *c_domlist;
>       int i, nb;
> 
> +     caml_enter_blocking_section();
>       c_domlist = libxl_list_domain(CTX, &nb);
> +     caml_leave_blocking_section();
> +
>       if (!c_domlist)
>               failwith_xl(ERROR_FAIL, "dominfo_list");
> 
> @@ -826,8 +918,12 @@ value stub_xl_dominfo_get(value ctx, value domid)
>       CAMLlocal1(dominfo);
>       libxl_dominfo c_dominfo;
>       int ret;
> +     uint32_t c_domid = Int_val(domid);
> +
> +     caml_enter_blocking_section();
> +     ret = libxl_domain_info(CTX, &c_dominfo, c_domid);
> +     caml_leave_blocking_section();
> 
> -     ret = libxl_domain_info(CTX, &c_dominfo, Int_val(domid));
>       if (ret != 0)
>               failwith_xl(ERROR_FAIL, "domain_info");
>       dominfo = Val_dominfo(&c_dominfo);
> @@ -841,8 +937,12 @@ value stub_xl_domain_sched_params_get(value ctx,
> value domid)
>       CAMLlocal1(scinfo);
>       libxl_domain_sched_params c_scinfo;
>       int ret;
> +     uint32_t c_domid = Int_val(domid);
> +
> +     caml_enter_blocking_section();
> +     ret = libxl_domain_sched_params_get(CTX, c_domid, &c_scinfo);
> +     caml_leave_blocking_section();
> 
> -     ret = libxl_domain_sched_params_get(CTX, Int_val(domid),
> &c_scinfo);
>       if (ret != 0)
>               failwith_xl(ret, "domain_sched_params_get");
> 
> @@ -858,10 +958,13 @@ value stub_xl_domain_sched_params_set(value
> ctx, value domid, value scinfo)
>       CAMLparam3(ctx, domid, scinfo);
>       libxl_domain_sched_params c_scinfo;
>       int ret;
> +     uint32_t c_domid = Int_val(domid);
> 
>       domain_sched_params_val(CTX, &c_scinfo, scinfo);
> 
> -     ret = libxl_domain_sched_params_set(CTX, Int_val(domid),
> &c_scinfo);
> +     caml_enter_blocking_section();
> +     ret = libxl_domain_sched_params_set(CTX, c_domid, &c_scinfo);
> +     caml_leave_blocking_section();
> 
>       libxl_domain_sched_params_dispose(&c_scinfo);
> 
> @@ -875,12 +978,15 @@ value stub_xl_send_trigger(value ctx, value domid,
> value trigger, value vcpuid)  {
>       CAMLparam4(ctx, domid, trigger, vcpuid);
>       int ret;
> +     uint32_t c_domid = Int_val(domid);
>       libxl_trigger c_trigger = LIBXL_TRIGGER_UNKNOWN;
> +     int c_vcpuid = Int_val(vcpuid);
> 
>       trigger_val(CTX, &c_trigger, trigger);
> 
> -     ret = libxl_send_trigger(CTX, Int_val(domid),
> -                              c_trigger, Int_val(vcpuid));
> +     caml_enter_blocking_section();
> +     ret = libxl_send_trigger(CTX, c_domid, c_trigger, c_vcpuid);
> +     caml_leave_blocking_section();
> 
>       if (ret != 0)
>               failwith_xl(ret, "send_trigger");
> @@ -892,8 +998,12 @@ value stub_xl_send_sysrq(value ctx, value domid,
> value sysrq)  {
>       CAMLparam3(ctx, domid, sysrq);
>       int ret;
> +     uint32_t c_domid = Int_val(domid);
> +     int c_sysrq = Int_val(sysrq);
> 
> -     ret = libxl_send_sysrq(CTX, Int_val(domid), Int_val(sysrq));
> +     caml_enter_blocking_section();
> +     ret = libxl_send_sysrq(CTX, c_domid, c_sysrq);
> +     caml_leave_blocking_section();
> 
>       if (ret != 0)
>               failwith_xl(ret, "send_sysrq");
> @@ -909,7 +1019,10 @@ value stub_xl_send_debug_keys(value ctx, value
> keys)
> 
>       c_keys = dup_String_val(keys);
> 
> +     caml_enter_blocking_section();
>       ret = libxl_send_debug_keys(CTX, c_keys);
> +     caml_leave_blocking_section();
> +
>       free(c_keys);
> 
>       if (ret != 0)
> @@ -933,9 +1046,12 @@ value stub_libxl_xen_console_read_start(value ctx,
> value clear)  {
>       CAMLparam2(ctx, clear);
>       CAMLlocal1(handle);
> +     int c_clear = Int_val(clear);
>       libxl_xen_console_reader *cr;
> 
> -     cr = libxl_xen_console_read_start(CTX, Int_val(clear));
> +     caml_enter_blocking_section();
> +     cr = libxl_xen_console_read_start(CTX, c_clear);
> +     caml_leave_blocking_section();
> 
>       handle =
> caml_alloc_custom(&libxl_console_reader_custom_operations, sizeof(cr), 0,
> 1);
>       Console_reader_val(handle) = cr;
> @@ -965,7 +1081,9 @@ value stub_libxl_xen_console_read_line(value ctx,
> value reader)
>       char *c_line;
>       libxl_xen_console_reader *cr = (libxl_xen_console_reader *)
> Console_reader_val(reader);
> 
> +     caml_enter_blocking_section();
>       ret = libxl_xen_console_read_line(CTX, cr, &c_line);
> +     caml_leave_blocking_section();
> 
>       if (ret < 0)
>               failwith_xl(ret, "xen_console_read_line"); @@ -982,7
> +1100,9 @@ value stub_libxl_xen_console_read_finish(value ctx, value
> reader)
>       CAMLparam2(ctx, reader);
>       libxl_xen_console_reader *cr = (libxl_xen_console_reader *)
> Console_reader_val(reader);
> 
> +     caml_enter_blocking_section();
>       libxl_xen_console_read_finish(CTX, cr);
> +     caml_leave_blocking_section();
> 
>       CAMLreturn(Val_unit);
>  }
> @@ -1074,6 +1194,7 @@ value Val_poll_events(short events)  int
> fd_register(void *user, int fd, void **for_app_registration_out,
>                       short events, void *for_libxl)  {
> +     caml_leave_blocking_section();
>       CAMLparam0();
>       CAMLlocalN(args, 4);
>       static value *func = NULL;
> @@ -1089,12 +1210,15 @@ int fd_register(void *user, int fd, void
> **for_app_registration_out,
>       args[3] = (value) for_libxl;
> 
>       caml_callbackN(*func, 4, args);
> -     CAMLreturn(0);
> +     CAMLdone;
> +     caml_enter_blocking_section();
> +     return 0;
>  }
> 
>  int fd_modify(void *user, int fd, void **for_app_registration_update,
>                     short events)
>  {
> +     caml_leave_blocking_section();
>       CAMLparam0();
>       CAMLlocalN(args, 3);
>       static value *func = NULL;
> @@ -1109,11 +1233,14 @@ int fd_modify(void *user, int fd, void
> **for_app_registration_update,
>       args[2] = Val_poll_events(events);
> 
>       caml_callbackN(*func, 3, args);
> -     CAMLreturn(0);
> +     CAMLdone;
> +     caml_enter_blocking_section();
> +     return 0;
>  }
> 
>  void fd_deregister(void *user, int fd, void *for_app_registration)  {
> +     caml_leave_blocking_section();
>       CAMLparam0();
>       CAMLlocalN(args, 2);
>       static value *func = NULL;
> @@ -1127,12 +1254,14 @@ void fd_deregister(void *user, int fd, void
> *for_app_registration)
>       args[1] = Val_int(fd);
> 
>       caml_callbackN(*func, 2, args);
> -     CAMLreturn0;
> +     CAMLdone;
> +     caml_enter_blocking_section();
>  }
> 
>  int timeout_register(void *user, void **for_app_registration_out,
>                            struct timeval abs, void *for_libxl)  {
> +     caml_leave_blocking_section();
>       CAMLparam0();
>       CAMLlocalN(args, 4);
>       static value *func = NULL;
> @@ -1148,12 +1277,15 @@ int timeout_register(void *user, void
> **for_app_registration_out,
>       args[3] = (value) for_libxl;
> 
>       caml_callbackN(*func, 4, args);
> -     CAMLreturn(0);
> +     CAMLdone;
> +     caml_enter_blocking_section();
> +     return 0;
>  }
> 
>  int timeout_modify(void *user, void **for_app_registration_update,
>                           struct timeval abs)  {
> +     caml_leave_blocking_section();
>       CAMLparam0();
>       static value *func = NULL;
> 
> @@ -1163,13 +1295,16 @@ int timeout_modify(void *user, void
> **for_app_registration_update,
>       }
> 
>       caml_callback(*func, (value) user);
> -     CAMLreturn(0);
> +     CAMLdone;
> +     caml_enter_blocking_section();
> +     return 0;
>  }
> 
>  void timeout_deregister(void *user, void *for_app_registration)  {
> +     caml_leave_blocking_section();
>       failwith_xl(ERROR_FAIL, "timeout_deregister not yet
> implemented");
> -     return;
> +     caml_enter_blocking_section();
>  }
> 
>  value stub_libxl_osevent_register_hooks(value ctx, value user) @@ -1186,7
> +1321,10 @@ value stub_libxl_osevent_register_hooks(value ctx, value user)
>       hooks->timeout_modify = timeout_modify;
>       hooks->timeout_deregister = timeout_deregister;
> 
> +     caml_enter_blocking_section();
>       libxl_osevent_register_hooks(CTX, hooks, (void *) user);
> +     caml_leave_blocking_section();
> +
>       result = caml_alloc(1, Abstract_tag);
>       *((libxl_osevent_hooks **) result) = hooks;
> 
> @@ -1197,15 +1335,25 @@ value stub_libxl_osevent_occurred_fd(value ctx,
> value for_libxl, value fd,
>       value events, value revents)
>  {
>       CAMLparam5(ctx, for_libxl, fd, events, revents);
> -     libxl_osevent_occurred_fd(CTX, (void *) for_libxl, Int_val(fd),
> -             Poll_events_val(events), Poll_events_val(revents));
> +     int c_fd = Int_val(fd);
> +     short c_events = Poll_events_val(events);
> +     short c_revents = Poll_events_val(revents);
> +
> +     caml_enter_blocking_section();
> +     libxl_osevent_occurred_fd(CTX, (void *) for_libxl, c_fd, c_events,
> c_revents);
> +     caml_leave_blocking_section();
> +
>       CAMLreturn(Val_unit);
>  }
> 
>  value stub_libxl_osevent_occurred_timeout(value ctx, value for_libxl)  {
>       CAMLparam2(ctx, for_libxl);
> +
> +     caml_enter_blocking_section();
>       libxl_osevent_occurred_timeout(CTX, (void *) for_libxl);
> +     caml_leave_blocking_section();
> +
>       CAMLreturn(Val_unit);
>  }
> 
> @@ -1216,6 +1364,7 @@ struct user_with_ctx {
> 
>  void event_occurs(void *user, libxl_event *event)  {
> +     caml_leave_blocking_section();
>       CAMLparam0();
>       CAMLlocalN(args, 2);
>       struct user_with_ctx *c_user = (struct user_with_ctx *) user; @@ -
> 1231,12 +1380,14 @@ void event_occurs(void *user, libxl_event *event)
>       libxl_event_free(c_user->ctx, event);
> 
>       caml_callbackN(*func, 2, args);
> -     CAMLreturn0;
> +     CAMLdone;
> +     caml_enter_blocking_section();
>  }
> 
>  void disaster(void *user, libxl_event_type type,
>                       const char *msg, int errnoval)  {
> +     caml_leave_blocking_section();
>       CAMLparam0();
>       CAMLlocalN(args, 4);
>       struct user_with_ctx *c_user = (struct user_with_ctx *) user; @@ -
> 1253,7 +1404,8 @@ void disaster(void *user, libxl_event_type type,
>       args[3] = Val_int(errnoval);
> 
>       caml_callbackN(*func, 4, args);
> -     CAMLreturn0;
> +     CAMLdone;
> +     caml_enter_blocking_section();
>  }
> 
>  value stub_libxl_event_register_callbacks(value ctx, value user) @@ -
> 1272,7 +1424,10 @@ value stub_libxl_event_register_callbacks(value ctx,
> value user)
>       hooks->event_occurs = event_occurs;
>       hooks->disaster = disaster;
> 
> +     caml_enter_blocking_section();
>       libxl_event_register_callbacks(CTX, hooks, (void *) c_user);
> +     caml_leave_blocking_section();
> +
>       result = caml_alloc(1, Abstract_tag);
>       *((libxl_event_hooks **) result) = hooks;
> 
> @@ -1282,9 +1437,13 @@ value stub_libxl_event_register_callbacks(value
> ctx, value user)  value stub_libxl_evenable_domain_death(value ctx, value
> domid, value user)  {
>       CAMLparam3(ctx, domid, user);
> +     uint32_t c_domid = Int_val(domid);
> +     int c_user = Int_val(user);
>       libxl_evgen_domain_death *evgen_out;
> 
> -     libxl_evenable_domain_death(CTX, Int_val(domid), Int_val(user),
> &evgen_out);
> +     caml_enter_blocking_section();
> +     libxl_evenable_domain_death(CTX, c_domid, c_user, &evgen_out);
> +     caml_leave_blocking_section();
> 
>       CAMLreturn(Val_unit);
>  }
> --
> 1.7.10.4


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