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* [glibc/nsz/bug19329] elf: Remove lazy tlsdesc relocation related code
@ 2021-02-15 11:54 Szabolcs Nagy
0 siblings, 0 replies; 2+ messages in thread
From: Szabolcs Nagy @ 2021-02-15 11:54 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=99e61c835b6365a54ee282392cc3241b2b7de46d
commit 99e61c835b6365a54ee282392cc3241b2b7de46d
Author: Szabolcs Nagy <szabolcs.nagy@arm.com>
Date: Thu Feb 11 13:24:47 2021 +0000
elf: Remove lazy tlsdesc relocation related code
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.
Diff:
---
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;
}
@@ -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
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
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
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
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
^ permalink raw reply [flat|nested] 2+ messages in thread
* [glibc/nsz/bug19329] elf: Remove lazy tlsdesc relocation related code
@ 2021-02-15 12:11 Szabolcs Nagy
0 siblings, 0 replies; 2+ messages in thread
From: Szabolcs Nagy @ 2021-02-15 12:11 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=191f5ae0f316e967e7e230fd9a919dce89d49b9f
commit 191f5ae0f316e967e7e230fd9a919dce89d49b9f
Author: Szabolcs Nagy <szabolcs.nagy@arm.com>
Date: Thu Feb 11 13:24:47 2021 +0000
elf: Remove lazy tlsdesc relocation related code
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.
Diff:
---
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;
}
@@ -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
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
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
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
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
^ permalink raw reply [flat|nested] 2+ messages in thread
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