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| author | Adhemerval Zanella <adhemerval.zanella@linaro.org> | 2018-05-09 10:32:25 -0300 |
|---|---|---|
| committer | Adhemerval Zanella <adhemerval.zanella@linaro.org> | 2019-01-03 18:38:14 -0200 |
| commit | 85c828a4626adda906f8844dc9c5a166c72d4f7d (patch) | |
| tree | 034152296ec94a9e33e360833068b01515fea4c7 /sysdeps | |
| parent | d0d7f85f66a19c3110d550c3c24247f7b4f2c58a (diff) | |
| download | glibc-85c828a4626adda906f8844dc9c5a166c72d4f7d.tar.gz glibc-85c828a4626adda906f8844dc9c5a166c72d4f7d.tar.xz glibc-85c828a4626adda906f8844dc9c5a166c72d4f7d.zip | |
x86_64: Remove wrong THREAD_ATOMIC_* macros
The x86 defines optimized THREAD_ATOMIC_* macros where reference always the current thread instead of the one indicated by input 'descr' argument. It work as long the input is the self thread pointer, however it generates wrong code if the semantic is to set a bit atomicialy from another thread. This is not an issue for current GLIBC usage, however the new cancellation code expects that some synchronization code to atomically set bits from different threads. The generic code generates an additional load to reference to TLS segment, for instance the code: THREAD_ATOMIC_BIT_SET (THREAD_SELF, cancelhandling, CANCELED_BIT); Compiles to: lock;orl $4, %fs:776 Where with patch changes it now compiles to: mov %fs:16,%rax lock;orl $4, 776(%rax) If some usage indeed proves to be a hotspot we can add an extra macro with a more descriptive name (THREAD_ATOMIC_BIT_SET_SELF for instance) where x86_64 might optimize it. Checked on x86_64-linux-gnu. * sysdeps/x86_64/nptl/tls.h (THREAD_ATOMIC_CMPXCHG_VAL, THREAD_ATOMIC_AND, THREAD_ATOMIC_BIT_SET): Remove macros.
Diffstat (limited to 'sysdeps')
| -rw-r--r-- | sysdeps/x86_64/nptl/tls.h | 37 |
1 files changed, 0 insertions, 37 deletions
diff --git a/sysdeps/x86_64/nptl/tls.h b/sysdeps/x86_64/nptl/tls.h index cb7f07ab7d..e25430a928 100644 --- a/sysdeps/x86_64/nptl/tls.h +++ b/sysdeps/x86_64/nptl/tls.h @@ -306,43 +306,6 @@ _Static_assert (offsetof (tcbhead_t, __glibc_unused2) == 0x80, }}) -/* Atomic compare and exchange on TLS, returning old value. */ -# define THREAD_ATOMIC_CMPXCHG_VAL(descr, member, newval, oldval) \ - ({ __typeof (descr->member) __ret; \ - __typeof (oldval) __old = (oldval); \ - if (sizeof (descr->member) == 4) \ - asm volatile (LOCK_PREFIX "cmpxchgl %2, %%fs:%P3" \ - : "=a" (__ret) \ - : "0" (__old), "r" (newval), \ - "i" (offsetof (struct pthread, member))); \ - else \ - /* Not necessary for other sizes in the moment. */ \ - abort (); \ - __ret; }) - - -/* Atomic logical and. */ -# define THREAD_ATOMIC_AND(descr, member, val) \ - (void) ({ if (sizeof ((descr)->member) == 4) \ - asm volatile (LOCK_PREFIX "andl %1, %%fs:%P0" \ - :: "i" (offsetof (struct pthread, member)), \ - "ir" (val)); \ - else \ - /* Not necessary for other sizes in the moment. */ \ - abort (); }) - - -/* Atomic set bit. */ -# define THREAD_ATOMIC_BIT_SET(descr, member, bit) \ - (void) ({ if (sizeof ((descr)->member) == 4) \ - asm volatile (LOCK_PREFIX "orl %1, %%fs:%P0" \ - :: "i" (offsetof (struct pthread, member)), \ - "ir" (1 << (bit))); \ - else \ - /* Not necessary for other sizes in the moment. */ \ - abort (); }) - - /* Set the stack guard field in TCB head. */ # define THREAD_SET_STACK_GUARD(value) \ THREAD_SETMEM (THREAD_SELF, header.stack_guard, value) |