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authorFlorian Weimer <fweimer@redhat.com>2021-07-09 10:59:22 +0200
committerFlorian Weimer <fweimer@redhat.com>2021-07-09 10:59:22 +0200
commit508ee037a30f1d4f6a1f8de2bd0d9866d4684625 (patch)
tree7784739365084bd7bef3913e01e58f31b7599ad5
parent01d780628278972cfa3630feeb74d7861b0fd5fc (diff)
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nptl: Use out-of-line wake function in __libc_lock_unlock slow path
This slightly reduces code size, as can be seen below. __libc_lock_unlock is usually used along with __libc_lock_lock in the same function. __libc_lock_lock already has an out-of-line slow path, so this change should not introduce many additional non-leaf functions. This change also fixes a link failure in 32-bit Arm thumb mode because commit 1f9c804fbd699104adefbce9e56d2c8aa711b6b9 ("nptl: Use internal low-level lock type for !IS_IN (libc)") introduced __libc_do_syscall calls outside of libc. Before x86-64: text data bss dec hex filename 1937748 20456 54896 2013100 1eb7ac libc.so.6 25601 856 12768 39225 9939 nss/libnss_db.so.2 40310 952 25144 66406 10366 nss/libnss_files.so.2 After x86-64: text data bss dec hex filename 1935312 20456 54896 2010664 1eae28 libc.so.6 25559 864 12768 39191 9917 nss/libnss_db.so.2 39764 960 25144 65868 1014c nss/libnss_files.so.2 Before i686: 2110961 11272 39144 2161377 20fae1 libc.so.6 27243 428 12652 40323 9d83 nss/libnss_db.so.2 43062 476 25028 68566 10bd6 nss/libnss_files.so.2 After i686: 2107347 11272 39144 2157763 20ecc3 libc.so.6 26929 432 12652 40013 9c4d nss/libnss_db.so.2 43132 480 25028 68640 10c20 nss/libnss_files.so.2 Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
-rw-r--r--nptl/Versions1
-rw-r--r--nptl/lowlevellock.c14
-rw-r--r--sysdeps/nptl/lowlevellock.h26
3 files changed, 33 insertions, 8 deletions
diff --git a/nptl/Versions b/nptl/Versions
index 2a75f013f2..3221de89d1 100644
--- a/nptl/Versions
+++ b/nptl/Versions
@@ -380,6 +380,7 @@ libc {
}
GLIBC_PRIVATE {
__libc_alloca_cutoff;
+ __lll_lock_wake_private;
__lll_lock_wait_private;
__nptl_create_event;
__nptl_death_event;
diff --git a/nptl/lowlevellock.c b/nptl/lowlevellock.c
index 2d077d8694..4f88178964 100644
--- a/nptl/lowlevellock.c
+++ b/nptl/lowlevellock.c
@@ -52,6 +52,20 @@ __lll_lock_wait (int *futex, int private)
}
libc_hidden_def (__lll_lock_wait)
+void
+__lll_lock_wake_private (int *futex)
+{
+ lll_futex_wake (futex, 1, LLL_PRIVATE);
+}
+libc_hidden_def (__lll_lock_wake_private)
+
+void
+__lll_lock_wake (int *futex, int private)
+{
+ lll_futex_wake (futex, 1, private);
+}
+libc_hidden_def (__lll_lock_wake)
+
#if ENABLE_ELISION_SUPPORT
int __pthread_force_elision __attribute__ ((nocommon));
libc_hidden_data_def (__pthread_force_elision)
diff --git a/sysdeps/nptl/lowlevellock.h b/sysdeps/nptl/lowlevellock.h
index be60c9ac28..4d95114ed3 100644
--- a/sysdeps/nptl/lowlevellock.h
+++ b/sysdeps/nptl/lowlevellock.h
@@ -125,6 +125,11 @@ libc_hidden_proto (__lll_lock_wait)
#define lll_cond_lock(futex, private) __lll_cond_lock (&(futex), private)
+extern void __lll_lock_wake_private (int *futex);
+libc_hidden_proto (__lll_lock_wake_private)
+extern void __lll_lock_wake (int *futex, int private);
+libc_hidden_proto (__lll_lock_wake)
+
/* This is an expression rather than a statement even though its value is
void, so that it can be used in a comma expression or as an expression
that's cast to void. */
@@ -137,14 +142,19 @@ libc_hidden_proto (__lll_lock_wait)
acquires the lock and when there will be no further lock acquisitions;
thus, we must not access the lock after releasing it, or those accesses
could be concurrent with mutex destruction or reuse of the memory. */
-#define __lll_unlock(futex, private) \
- ((void) \
- ({ \
- int *__futex = (futex); \
- int __private = (private); \
- int __oldval = atomic_exchange_rel (__futex, 0); \
- if (__glibc_unlikely (__oldval > 1)) \
- lll_futex_wake (__futex, 1, __private); \
+#define __lll_unlock(futex, private) \
+ ((void) \
+ ({ \
+ int *__futex = (futex); \
+ int __private = (private); \
+ int __oldval = atomic_exchange_rel (__futex, 0); \
+ if (__glibc_unlikely (__oldval > 1)) \
+ { \
+ if (__builtin_constant_p (private) && (private) == LLL_PRIVATE) \
+ __lll_lock_wake_private (__futex); \
+ else \
+ __lll_lock_wake (__futex, __private); \
+ } \
}))
#define lll_unlock(futex, private) \
__lll_unlock (&(futex), private)