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AArch64: Prioritise init_have_lse_atomics constructor [PR 105708]

Message ID DB6PR0801MB18791C9A9C5C8213D039B75683D79@DB6PR0801MB1879.eurprd08.prod.outlook.com
State New
Headers
Series AArch64: Prioritise init_have_lse_atomics constructor [PR 105708] |

Commit Message

Wilco Dijkstra May 24, 2022, 4:45 p.m. UTC 
  Increase the priority of the init_have_lse_atomics constructor so it runs
before other constructors. This improves chances that rr works when LSE
atomics are supported.

Regress and bootstrap pass, OK for commit?

2022-05-24  Wilco Dijkstra  <wdijkstr@arm.com>

libgcc/
        PR libgcc/105708
        * config/aarch64/lse-init.c: Increase constructor priority.

---

Comments

Richard Sandiford May 25, 2022, 7:20 a.m. UTC | #1 
Wilco Dijkstra <Wilco.Dijkstra@arm.com> writes:
> Increase the priority of the init_have_lse_atomics constructor so it runs
> before other constructors. This improves chances that rr works when LSE
> atomics are supported.

Can you add a comment above the function explaining why we chose 90
in particular?  I see 100 was originally suggested in the PR.

Thanks,
Richard

> Regress and bootstrap pass, OK for commit?
>
> 2022-05-24  Wilco Dijkstra  <wdijkstr@arm.com>
>
> libgcc/
>         PR libgcc/105708
>         * config/aarch64/lse-init.c: Increase constructor priority.
>
> ---
> diff --git a/libgcc/config/aarch64/lse-init.c b/libgcc/config/aarch64/lse-init.c
> index fc875b7fe80e947623e570eac130e7a14b516551..988882d91dfeed77f299aa610d72091499271490 100644
> --- a/libgcc/config/aarch64/lse-init.c
> +++ b/libgcc/config/aarch64/lse-init.c
> @@ -38,7 +38,7 @@ _Bool __aarch64_have_lse_atomics
>
>  unsigned long int __getauxval (unsigned long int);
>
> -static void __attribute__((constructor))
> +static void __attribute__((constructor (90)))
>  init_have_lse_atomics (void)
>  {
>    unsigned long hwcap = __getauxval (AT_HWCAP);
Wilco Dijkstra May 25, 2022, 10:42 a.m. UTC | #2 
Hi Richard,

I've added a comment - as usual it's just a number. A quick grep in gcc and
glibc showed that priorities 98-101 are used, so I just went a bit below so it
has a higher priority than typical initializations.

Cheers,
Wilco

Here is v2:

Increase the priority of the init_have_lse_atomics constructor so it runs
before other constructors. This improves chances that rr works when LSE
atomics are supported.

Regress and bootstrap pass, OK for commit?

2022-05-24  Wilco Dijkstra  <wdijkstr@arm.com>

libgcc/
        PR libgcc/105708
        * config/aarch64/lse-init.c: Increase constructor priority.

---

diff --git a/libgcc/config/aarch64/lse-init.c b/libgcc/config/aarch64/lse-init.c
index fc875b7fe80e947623e570eac130e7a14b516551..33b97c8d766895cf0101a851e1dc4ed6a1a053d9 100644
--- a/libgcc/config/aarch64/lse-init.c
+++ b/libgcc/config/aarch64/lse-init.c
@@ -38,7 +38,9 @@ _Bool __aarch64_have_lse_atomics
 
 unsigned long int __getauxval (unsigned long int);
 
-static void __attribute__((constructor))
+/* Use a higher priority to ensure it runs before user constructors
+   and library constructors with priority 100. */
+static void __attribute__((constructor (90)))
 init_have_lse_atomics (void)
 {
   unsigned long hwcap = __getauxval (AT_HWCAP);
Richard Sandiford May 25, 2022, 11:57 a.m. UTC | #3 
Wilco Dijkstra <Wilco.Dijkstra@arm.com> writes:
> Hi Richard,
>
> I've added a comment - as usual it's just a number. A quick grep in gcc and
> glibc showed that priorities 98-101 are used, so I just went a bit below so it
> has a higher priority than typical initializations.

Thanks.  OK for trunk, and for backports after a trial period.

Richard

> Cheers,
> Wilco
>
> Here is v2:
>
> Increase the priority of the init_have_lse_atomics constructor so it runs
> before other constructors. This improves chances that rr works when LSE
> atomics are supported.
>
> Regress and bootstrap pass, OK for commit?
>
> 2022-05-24  Wilco Dijkstra  <wdijkstr@arm.com>
>
> libgcc/
>         PR libgcc/105708
>         * config/aarch64/lse-init.c: Increase constructor priority.
>
> ---
>
> diff --git a/libgcc/config/aarch64/lse-init.c b/libgcc/config/aarch64/lse-init.c
> index fc875b7fe80e947623e570eac130e7a14b516551..33b97c8d766895cf0101a851e1dc4ed6a1a053d9 100644
> --- a/libgcc/config/aarch64/lse-init.c
> +++ b/libgcc/config/aarch64/lse-init.c
> @@ -38,7 +38,9 @@ _Bool __aarch64_have_lse_atomics
>
>  unsigned long int __getauxval (unsigned long int);
>
> -static void __attribute__((constructor))
> +/* Use a higher priority to ensure it runs before user constructors
> +   and library constructors with priority 100. */
> +static void __attribute__((constructor (90)))
>  init_have_lse_atomics (void)
>  {
>    unsigned long hwcap = __getauxval (AT_HWCAP);
diff mbox series

Patch

diff --git a/libgcc/config/aarch64/lse-init.c b/libgcc/config/aarch64/lse-init.c
index fc875b7fe80e947623e570eac130e7a14b516551..988882d91dfeed77f299aa610d72091499271490 100644
--- a/libgcc/config/aarch64/lse-init.c
+++ b/libgcc/config/aarch64/lse-init.c
@@ -38,7 +38,7 @@  _Bool __aarch64_have_lse_atomics
 
 unsigned long int __getauxval (unsigned long int);
 
-static void __attribute__((constructor))
+static void __attribute__((constructor (90)))
 init_have_lse_atomics (void)
 {
   unsigned long hwcap = __getauxval (AT_HWCAP);