libgomp: Fix default value of GOMP_SPINCOUNT [PR 109062]

  Hi,

When OMP_WAIT_POLICY is not specified, current implementation will cause
icv flag GOMP_ICV_WAIT_POLICY unset, so global variable wait_policy
will remain its uninitialized value. Set it to -1 when the flag is not
specified to keep GOMP_SPINCOUNT behavior consistent with its description.

Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?

libgomp/ChangeLog:

	PR libgomp/109062
	* env.c (initialize_env): Set wait_policy to -1 if
	OMP_WAIT_POLICY is not specified.
	* testsuite/libgomp.c-c++-common/pr109062.c: New test.
---
 libgomp/env.c                                     |  2 ++
 libgomp/testsuite/libgomp.c-c++-common/pr109062.c | 14 ++++++++++++++
 2 files changed, 16 insertions(+)
 create mode 100644 libgomp/testsuite/libgomp.c-c++-common/pr109062.c
  

On Wed, Mar 08, 2023 at 02:31:38PM +0800, Hongyu Wang wrote:
> Hi,
> 
> When OMP_WAIT_POLICY is not specified, current implementation will cause
> icv flag GOMP_ICV_WAIT_POLICY unset, so global variable wait_policy
> will remain its uninitialized value. Set it to -1 when the flag is not
> specified to keep GOMP_SPINCOUNT behavior consistent with its description.
> 
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
> 
> libgomp/ChangeLog:
> 
> 	PR libgomp/109062
> 	* env.c (initialize_env): Set wait_policy to -1 if
> 	OMP_WAIT_POLICY is not specified.
> 	* testsuite/libgomp.c-c++-common/pr109062.c: New test.

I think the right spot to fix this would be instead in initialize_icvs,
change the
  icvs->wait_policy = 0;
in there to
  icvs->wait_policy = -1;
That way it will be the default for all the devices, not just the
initial one.

Ok for trunk with that change if it works.

> diff --git a/libgomp/env.c b/libgomp/env.c
> index c41c1f852cc..fa36a8697d6 100644
> --- a/libgomp/env.c
> +++ b/libgomp/env.c
> @@ -2249,6 +2249,8 @@ initialize_env (void)
>      wait_policy = none->icvs.wait_policy;
>    else if (all != NULL && gomp_get_icv_flag (all->flags, GOMP_ICV_WAIT_POLICY))
>      wait_policy = all->icvs.wait_policy;
> +  else
> +    wait_policy = -1;
>  
>    if (!parse_spincount ("GOMP_SPINCOUNT", &gomp_spin_count_var))
>      {
> diff --git a/libgomp/testsuite/libgomp.c-c++-common/pr109062.c b/libgomp/testsuite/libgomp.c-c++-common/pr109062.c
> new file mode 100644
> index 00000000000..5c7c287dafd
> --- /dev/null
> +++ b/libgomp/testsuite/libgomp.c-c++-common/pr109062.c
> @@ -0,0 +1,14 @@
> +/* { dg-do run } */
> +
> +#include <omp.h>
> +#include <stdlib.h>
> +
> +int
> +main ()
> +{
> +  omp_display_env (1);
> +
> +  return 0;
> +}
> +
> +/* { dg-output ".*\\\[host] GOMP_SPINCOUNT = '300000'.*" { target native } } */
> -- 
> 2.31.1

	Jakub
  

> I think the right spot to fix this would be instead in initialize_icvs,
> change the
>   icvs->wait_policy = 0;
> in there to
>   icvs->wait_policy = -1;
> That way it will be the default for all the devices, not just the
> initial one.

It doesn't work, for the code that determines value of wait_policy:

if (none != NULL && gomp_get_icv_flag (none->flags, GOMP_ICV_WAIT_POLICY))
  wait_policy = none->icvs.wait_policy;
else if (all != NULL && gomp_get_icv_flag (all->flags, GOMP_ICV_WAIT_POLICY))
  wait_policy = all->icvs.wait_policy;

gomp_get_icv_flag (none->flags, GOMP_ICV_WAIT_POLICY) returns true only when
OMP_WAIT_POLICY is explicitly set, so the initial icvs->wait_policy
could not affect the global wait_policy that used to set
GOMP_SPINCOUNT.
  

Hongyu Wang <wwwhhhyyy333@gmail.com> 于2023年3月8日周三 16:07写道：
>
> > I think the right spot to fix this would be instead in initialize_icvs,
> > change the
> >   icvs->wait_policy = 0;
> > in there to
> >   icvs->wait_policy = -1;
> > That way it will be the default for all the devices, not just the
> > initial one.
>
> It doesn't work, for the code that determines value of wait_policy:
>
> if (none != NULL && gomp_get_icv_flag (none->flags, GOMP_ICV_WAIT_POLICY))
>   wait_policy = none->icvs.wait_policy;
> else if (all != NULL && gomp_get_icv_flag (all->flags, GOMP_ICV_WAIT_POLICY))
>   wait_policy = all->icvs.wait_policy;
>
> gomp_get_icv_flag (none->flags, GOMP_ICV_WAIT_POLICY) returns true only when
> OMP_WAIT_POLICY is explicitly set, so the initial icvs->wait_policy
> could not affect the global wait_policy that used to set
> GOMP_SPINCOUNT.

Also the global variable wait_policy here is only used for setting
spin_count related values that do not
belong to any ICV, so there is no need to set icvs->wait_policy since
for OMP_WAIT_POLICY_(DEV|ALL)
itself only has value 0 for passive and value 1 for active.
  

On Wed, Mar 08, 2023 at 04:21:46PM +0800, Hongyu Wang wrote:
> Hongyu Wang <wwwhhhyyy333@gmail.com> 于2023年3月8日周三 16:07写道：
> >
> > > I think the right spot to fix this would be instead in initialize_icvs,
> > > change the
> > >   icvs->wait_policy = 0;
> > > in there to
> > >   icvs->wait_policy = -1;
> > > That way it will be the default for all the devices, not just the
> > > initial one.
> >
> > It doesn't work, for the code that determines value of wait_policy:
> >
> > if (none != NULL && gomp_get_icv_flag (none->flags, GOMP_ICV_WAIT_POLICY))
> >   wait_policy = none->icvs.wait_policy;
> > else if (all != NULL && gomp_get_icv_flag (all->flags, GOMP_ICV_WAIT_POLICY))
> >   wait_policy = all->icvs.wait_policy;
> >
> > gomp_get_icv_flag (none->flags, GOMP_ICV_WAIT_POLICY) returns true only when
> > OMP_WAIT_POLICY is explicitly set, so the initial icvs->wait_policy
> > could not affect the global wait_policy that used to set
> > GOMP_SPINCOUNT.
> 
> Also the global variable wait_policy here is only used for setting
> spin_count related values that do not
> belong to any ICV, so there is no need to set icvs->wait_policy since
> for OMP_WAIT_POLICY_(DEV|ALL)
> itself only has value 0 for passive and value 1 for active.

Seems for many ICVs the default values are done through
gomp_default_icv_values, but that doesn't cover wait_policy.
For other vars, the defaults are provided through just initializers of
those vars on the var definitions, e.g.:
char *gomp_affinity_format_var = "level %L thread %i affinity %A";
So, I'd do the initialize_icvs change and change
static int wait_policy;
to
static int wait_policy = -1;

	Jakub
  

> Seems for many ICVs the default values are done through
> gomp_default_icv_values, but that doesn't cover wait_policy.
> For other vars, the defaults are provided through just initializers of
> those vars on the var definitions, e.g.:
> char *gomp_affinity_format_var = "level %L thread %i affinity %A";
> So, I'd do the initialize_icvs change and change
> static int wait_policy;
> to
> static int wait_policy = -1;

Agreed, here is the updated patch, ok for trunk?

When OMP_WAIT_POLICY is not specified, current implementation will cause
icv flag GOMP_ICV_WAIT_POLICY unset, so global variable wait_policy
will remain its uninitialized value. Initialize it to -1 to make
GOMP_SPINCOUNT behavior consistent with its description.

libgomp/ChangeLog:

PR libgomp/109062
* env.c (wait_policy): Initialize to -1.
(initialize_icvs): Initialize icvs->wait_policy to -1.
* testsuite/libgomp.c-c++-common/pr109062.c: New test.
---
 libgomp/env.c                                     |  4 ++--
 libgomp/testsuite/libgomp.c-c++-common/pr109062.c | 14 ++++++++++++++
 2 files changed, 16 insertions(+), 2 deletions(-)
 create mode 100644 libgomp/testsuite/libgomp.c-c++-common/pr109062.c

diff --git a/libgomp/env.c b/libgomp/env.c
index c41c1f852cc..e7a035b593c 100644
--- a/libgomp/env.c
+++ b/libgomp/env.c
@@ -124,7 +124,7 @@ int goacc_default_dims[GOMP_DIM_MAX];

 #ifndef LIBGOMP_OFFLOADED_ONLY

-static int wait_policy;
+static int wait_policy = -1;
 static unsigned long stacksize = GOMP_DEFAULT_STACKSIZE;

 static void
@@ -1981,7 +1981,7 @@ initialize_icvs (struct gomp_initial_icvs *icvs)
   icvs->bind_var = gomp_default_icv_values.bind_var;
   icvs->nteams_var = gomp_default_icv_values.nteams_var;
   icvs->teams_thread_limit_var =
gomp_default_icv_values.teams_thread_limit_var;
-  icvs->wait_policy = 0;
+  icvs->wait_policy = -1;
 }

 /* Helper function for initialize_env to add a device specific ICV value
diff --git a/libgomp/testsuite/libgomp.c-c++-common/pr109062.c
b/libgomp/testsuite/libgomp.c-c++-common/pr109062.c
new file mode 100644
index 00000000000..5c7c287dafd
--- /dev/null
+++ b/libgomp/testsuite/libgomp.c-c++-common/pr109062.c
@@ -0,0 +1,14 @@
+/* { dg-do run } */
+
+#include <omp.h>
+#include <stdlib.h>
+
+int
+main ()
+{
+  omp_display_env (1);
+
+  return 0;
+}
+
+/* { dg-output ".*\\\[host] GOMP_SPINCOUNT = '300000'.*" { target native } } */
  

On Wed, Mar 08, 2023 at 04:54:20PM +0800, Hongyu Wang wrote:
> > Seems for many ICVs the default values are done through
> > gomp_default_icv_values, but that doesn't cover wait_policy.
> > For other vars, the defaults are provided through just initializers of
> > those vars on the var definitions, e.g.:
> > char *gomp_affinity_format_var = "level %L thread %i affinity %A";
> > So, I'd do the initialize_icvs change and change
> > static int wait_policy;
> > to
> > static int wait_policy = -1;
> 
> Agreed, here is the updated patch, ok for trunk?
> 
> When OMP_WAIT_POLICY is not specified, current implementation will cause
> icv flag GOMP_ICV_WAIT_POLICY unset, so global variable wait_policy
> will remain its uninitialized value. Initialize it to -1 to make
> GOMP_SPINCOUNT behavior consistent with its description.
> 
> libgomp/ChangeLog:
> 
> PR libgomp/109062
> * env.c (wait_policy): Initialize to -1.
> (initialize_icvs): Initialize icvs->wait_policy to -1.
> * testsuite/libgomp.c-c++-common/pr109062.c: New test.

Ok, thanks.

	Jakub