[v2,13/14] elf: Remove lazy tlsdesc relocation related code
Commit Message
Remove generic tlsdesc code related to lazy tlsdesc processing since
lazy tlsdesc relocation is no longer supported. This includes removing
GL(dl_load_lock) from _dl_make_tlsdesc_dynamic which is only called at
load time when that lock is already held.
Added a documentation comment too.
---
elf/tlsdeschtab.h | 53 +++++----------------------------------
sysdeps/aarch64/tlsdesc.c | 1 -
sysdeps/arm/tlsdesc.c | 1 -
sysdeps/i386/tlsdesc.c | 1 -
sysdeps/x86_64/tlsdesc.c | 1 -
5 files changed, 6 insertions(+), 51 deletions(-)
Comments
On 13/04/2021 05:21, Szabolcs Nagy via Libc-alpha wrote:
> Remove generic tlsdesc code related to lazy tlsdesc processing since
> lazy tlsdesc relocation is no longer supported. This includes removing
> GL(dl_load_lock) from _dl_make_tlsdesc_dynamic which is only called at
> load time when that lock is already held.
>
> Added a documentation comment too.
LGTM, thanks.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
> ---
> elf/tlsdeschtab.h | 53 +++++----------------------------------
> sysdeps/aarch64/tlsdesc.c | 1 -
> sysdeps/arm/tlsdesc.c | 1 -
> sysdeps/i386/tlsdesc.c | 1 -
> sysdeps/x86_64/tlsdesc.c | 1 -
> 5 files changed, 6 insertions(+), 51 deletions(-)
>
> diff --git a/elf/tlsdeschtab.h b/elf/tlsdeschtab.h
> index 21695fd1e9..85bd0415e1 100644
> --- a/elf/tlsdeschtab.h
> +++ b/elf/tlsdeschtab.h
> @@ -78,6 +78,10 @@ map_generation (struct link_map *map)
> return GL(dl_tls_generation) + 1;
> }
>
> +/* Returns the data pointer for a given map and tls offset that is used
> + to fill in one of the GOT entries referenced by a TLSDESC relocation
> + when using dynamic TLS. This requires allocation, returns NULL on
> + allocation failure. */
> void *
> _dl_make_tlsdesc_dynamic (struct link_map *map, size_t ti_offset)
> {
> @@ -85,18 +89,12 @@ _dl_make_tlsdesc_dynamic (struct link_map *map, size_t ti_offset)
> void **entry;
> struct tlsdesc_dynamic_arg *td, test;
>
> - /* FIXME: We could use a per-map lock here, but is it worth it? */
> - __rtld_lock_lock_recursive (GL(dl_load_lock));
> -
> ht = map->l_mach.tlsdesc_table;
> if (! ht)
> {
> ht = htab_create ();
> if (! ht)
> - {
> - __rtld_lock_unlock_recursive (GL(dl_load_lock));
> - return 0;
> - }
> + return 0;
> map->l_mach.tlsdesc_table = ht;
> }
>
Ok.
> @@ -104,15 +102,11 @@ _dl_make_tlsdesc_dynamic (struct link_map *map, size_t ti_offset)
> test.tlsinfo.ti_offset = ti_offset;
> entry = htab_find_slot (ht, &test, 1, hash_tlsdesc, eq_tlsdesc);
> if (! entry)
> - {
> - __rtld_lock_unlock_recursive (GL(dl_load_lock));
> - return 0;
> - }
> + return 0;
>
> if (*entry)
> {
> td = *entry;
> - __rtld_lock_unlock_recursive (GL(dl_load_lock));
> return td;
> }
>
Ok.
> @@ -122,44 +116,9 @@ _dl_make_tlsdesc_dynamic (struct link_map *map, size_t ti_offset)
> thread. */
> td->gen_count = map_generation (map);
> td->tlsinfo = test.tlsinfo;
> -
> - __rtld_lock_unlock_recursive (GL(dl_load_lock));
> return td;
> }
>
> # endif /* SHARED */
>
> -/* The idea of the following two functions is to stop multiple threads
> - from attempting to resolve the same TLS descriptor without busy
> - waiting. Ideally, we should be able to release the lock right
> - after changing td->entry, and then using say a condition variable
> - or a futex wake to wake up any waiting threads, but let's try to
> - avoid introducing such dependencies. */
> -
> -static int
> -__attribute__ ((unused))
> -_dl_tlsdesc_resolve_early_return_p (struct tlsdesc volatile *td, void *caller)
> -{
> - if (caller != atomic_load_relaxed (&td->entry))
> - return 1;
> -
> - __rtld_lock_lock_recursive (GL(dl_load_lock));
> - if (caller != atomic_load_relaxed (&td->entry))
> - {
> - __rtld_lock_unlock_recursive (GL(dl_load_lock));
> - return 1;
> - }
> -
> - atomic_store_relaxed (&td->entry, _dl_tlsdesc_resolve_hold);
> -
> - return 0;
> -}
> -
> -static void
> -__attribute__ ((unused))
> -_dl_tlsdesc_wake_up_held_fixups (void)
> -{
> - __rtld_lock_unlock_recursive (GL(dl_load_lock));
> -}
> -
> #endif
Ok.
> diff --git a/sysdeps/aarch64/tlsdesc.c b/sysdeps/aarch64/tlsdesc.c
> index 9b6a8b0ec4..3c1bcd8fe6 100644
> --- a/sysdeps/aarch64/tlsdesc.c
> +++ b/sysdeps/aarch64/tlsdesc.c
> @@ -22,7 +22,6 @@
> #include <tls.h>
> #include <dl-tlsdesc.h>
> #include <dl-unmap-segments.h>
> -#define _dl_tlsdesc_resolve_hold 0
> #include <tlsdeschtab.h>
>
> /* Unmap the dynamic object, but also release its TLS descriptor table
Ok.
> diff --git a/sysdeps/arm/tlsdesc.c b/sysdeps/arm/tlsdesc.c
> index 2f70adef5c..b3d1735af4 100644
> --- a/sysdeps/arm/tlsdesc.c
> +++ b/sysdeps/arm/tlsdesc.c
> @@ -20,7 +20,6 @@
> #include <tls.h>
> #include <dl-tlsdesc.h>
> #include <dl-unmap-segments.h>
> -#define _dl_tlsdesc_resolve_hold 0
> #include <tlsdeschtab.h>
>
> /* Unmap the dynamic object, but also release its TLS descriptor table
Ok.
> diff --git a/sysdeps/i386/tlsdesc.c b/sysdeps/i386/tlsdesc.c
> index 436a21f66b..364c7769ce 100644
> --- a/sysdeps/i386/tlsdesc.c
> +++ b/sysdeps/i386/tlsdesc.c
> @@ -20,7 +20,6 @@
> #include <tls.h>
> #include <dl-tlsdesc.h>
> #include <dl-unmap-segments.h>
> -#define _dl_tlsdesc_resolve_hold 0
> #include <tlsdeschtab.h>
>
> /* Unmap the dynamic object, but also release its TLS descriptor table
Ok.
> diff --git a/sysdeps/x86_64/tlsdesc.c b/sysdeps/x86_64/tlsdesc.c
> index ecf864d6ee..3bb80517a3 100644
> --- a/sysdeps/x86_64/tlsdesc.c
> +++ b/sysdeps/x86_64/tlsdesc.c
> @@ -20,7 +20,6 @@
> #include <tls.h>
> #include <dl-tlsdesc.h>
> #include <dl-unmap-segments.h>
> -#define _dl_tlsdesc_resolve_hold 0
> #include <tlsdeschtab.h>
>
> /* Unmap the dynamic object, but also release its TLS descriptor table
>
Ok.
@@ -78,6 +78,10 @@ map_generation (struct link_map *map)
return GL(dl_tls_generation) + 1;
}
+/* Returns the data pointer for a given map and tls offset that is used
+ to fill in one of the GOT entries referenced by a TLSDESC relocation
+ when using dynamic TLS. This requires allocation, returns NULL on
+ allocation failure. */
void *
_dl_make_tlsdesc_dynamic (struct link_map *map, size_t ti_offset)
{
@@ -85,18 +89,12 @@ _dl_make_tlsdesc_dynamic (struct link_map *map, size_t ti_offset)
void **entry;
struct tlsdesc_dynamic_arg *td, test;
- /* FIXME: We could use a per-map lock here, but is it worth it? */
- __rtld_lock_lock_recursive (GL(dl_load_lock));
-
ht = map->l_mach.tlsdesc_table;
if (! ht)
{
ht = htab_create ();
if (! ht)
- {
- __rtld_lock_unlock_recursive (GL(dl_load_lock));
- return 0;
- }
+ return 0;
map->l_mach.tlsdesc_table = ht;
}
@@ -104,15 +102,11 @@ _dl_make_tlsdesc_dynamic (struct link_map *map, size_t ti_offset)
test.tlsinfo.ti_offset = ti_offset;
entry = htab_find_slot (ht, &test, 1, hash_tlsdesc, eq_tlsdesc);
if (! entry)
- {
- __rtld_lock_unlock_recursive (GL(dl_load_lock));
- return 0;
- }
+ return 0;
if (*entry)
{
td = *entry;
- __rtld_lock_unlock_recursive (GL(dl_load_lock));
return td;
}
@@ -122,44 +116,9 @@ _dl_make_tlsdesc_dynamic (struct link_map *map, size_t ti_offset)
thread. */
td->gen_count = map_generation (map);
td->tlsinfo = test.tlsinfo;
-
- __rtld_lock_unlock_recursive (GL(dl_load_lock));
return td;
}
# endif /* SHARED */
-/* The idea of the following two functions is to stop multiple threads
- from attempting to resolve the same TLS descriptor without busy
- waiting. Ideally, we should be able to release the lock right
- after changing td->entry, and then using say a condition variable
- or a futex wake to wake up any waiting threads, but let's try to
- avoid introducing such dependencies. */
-
-static int
-__attribute__ ((unused))
-_dl_tlsdesc_resolve_early_return_p (struct tlsdesc volatile *td, void *caller)
-{
- if (caller != atomic_load_relaxed (&td->entry))
- return 1;
-
- __rtld_lock_lock_recursive (GL(dl_load_lock));
- if (caller != atomic_load_relaxed (&td->entry))
- {
- __rtld_lock_unlock_recursive (GL(dl_load_lock));
- return 1;
- }
-
- atomic_store_relaxed (&td->entry, _dl_tlsdesc_resolve_hold);
-
- return 0;
-}
-
-static void
-__attribute__ ((unused))
-_dl_tlsdesc_wake_up_held_fixups (void)
-{
- __rtld_lock_unlock_recursive (GL(dl_load_lock));
-}
-
#endif
@@ -22,7 +22,6 @@
#include <tls.h>
#include <dl-tlsdesc.h>
#include <dl-unmap-segments.h>
-#define _dl_tlsdesc_resolve_hold 0
#include <tlsdeschtab.h>
/* Unmap the dynamic object, but also release its TLS descriptor table
@@ -20,7 +20,6 @@
#include <tls.h>
#include <dl-tlsdesc.h>
#include <dl-unmap-segments.h>
-#define _dl_tlsdesc_resolve_hold 0
#include <tlsdeschtab.h>
/* Unmap the dynamic object, but also release its TLS descriptor table
@@ -20,7 +20,6 @@
#include <tls.h>
#include <dl-tlsdesc.h>
#include <dl-unmap-segments.h>
-#define _dl_tlsdesc_resolve_hold 0
#include <tlsdeschtab.h>
/* Unmap the dynamic object, but also release its TLS descriptor table
@@ -20,7 +20,6 @@
#include <tls.h>
#include <dl-tlsdesc.h>
#include <dl-unmap-segments.h>
-#define _dl_tlsdesc_resolve_hold 0
#include <tlsdeschtab.h>
/* Unmap the dynamic object, but also release its TLS descriptor table