commit 37f8abad1c7b274e66eaf2d04684bd8a7ba0bcef
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Mon Jan 30 18:07:32 2017 -0200
nptl: Remove COLORING_INCREMENT
This patch removes the COLORING_INCREMENT define and usage on allocatestack.c.
It has not been used since 564cd8b67ec487f (glibc-2.3.3) by any architecture.
The idea is to simplify the code by removing obsolete code.
* nptl/allocatestack.c [COLORING_INCREMENT] (nptl_ncreated): Remove.
(allocate_stack): Remove COLORING_INCREMENT usage.
* nptl/stack-aliasing.h (COLORING_INCREMENT). Likewise.
* sysdeps/i386/i686/stack-aliasing.h (COLORING_INCREMENT): Likewise.
Conflicts:
nptl/allocatestack.c
Textual conflict due to missing backport of commit
a1ffb40e32741f992c743e7b16c061fefa3747ac (Use glibc_likely instead
__builtin_expect.).
diff --git a/nptl/allocatestack.c b/nptl/allocatestack.c
index 0fba6ce3474e8b35..00f9dcffe721a6b3 100644
--- a/nptl/allocatestack.c
+++ b/nptl/allocatestack.c
@@ -124,11 +124,6 @@ static uintptr_t in_flight_stack;
list_t __stack_user __attribute__ ((nocommon));
hidden_data_def (__stack_user)
-#if COLORING_INCREMENT != 0
-/* Number of threads created. */
-static unsigned int nptl_ncreated;
-#endif
-
/* Check whether the stack is still used or not. */
#define FREE_P(descr) ((descr)->tid <= 0)
@@ -456,14 +451,6 @@ allocate_stack (const struct pthread_attr *attr, struct pthread **pdp,
const int prot = (PROT_READ | PROT_WRITE
| ((GL(dl_stack_flags) & PF_X) ? PROT_EXEC : 0));
-#if COLORING_INCREMENT != 0
- /* Add one more page for stack coloring. Don't do it for stacks
- with 16 times pagesize or larger. This might just cause
- unnecessary misalignment. */
- if (size <= 16 * pagesize_m1)
- size += pagesize_m1 + 1;
-#endif
-
/* Adjust the stack size for alignment. */
size &= ~__static_tls_align_m1;
assert (size != 0);
@@ -506,34 +493,11 @@ allocate_stack (const struct pthread_attr *attr, struct pthread **pdp,
So we can never get a null pointer back from mmap. */
assert (mem != NULL);
-#if COLORING_INCREMENT != 0
- /* Atomically increment NCREATED. */
- unsigned int ncreated = atomic_increment_val (&nptl_ncreated);
-
- /* We chose the offset for coloring by incrementing it for
- every new thread by a fixed amount. The offset used
- module the page size. Even if coloring would be better
- relative to higher alignment values it makes no sense to
- do it since the mmap() interface does not allow us to
- specify any alignment for the returned memory block. */
- size_t coloring = (ncreated * COLORING_INCREMENT) & pagesize_m1;
-
- /* Make sure the coloring offsets does not disturb the alignment
- of the TCB and static TLS block. */
- if (__builtin_expect ((coloring & __static_tls_align_m1) != 0, 0))
- coloring = (((coloring + __static_tls_align_m1)
- & ~(__static_tls_align_m1))
- & ~pagesize_m1);
-#else
- /* Unless specified we do not make any adjustments. */
-# define coloring 0
-#endif
-
/* Place the thread descriptor at the end of the stack. */
#if TLS_TCB_AT_TP
- pd = (struct pthread *) ((char *) mem + size - coloring) - 1;
+ pd = (struct pthread *) ((char *) mem + size) - 1;
#elif TLS_DTV_AT_TP
- pd = (struct pthread *) ((((uintptr_t) mem + size - coloring
+ pd = (struct pthread *) ((((uintptr_t) mem + size
- __static_tls_size)
& ~__static_tls_align_m1)
- TLS_PRE_TCB_SIZE);
diff --git a/nptl/stack-aliasing.h b/nptl/stack-aliasing.h
index 526b54e18f7e0a27..62fdc9265e0038e6 100644
--- a/nptl/stack-aliasing.h
+++ b/nptl/stack-aliasing.h
@@ -16,12 +16,6 @@
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
-/* This is a number of bytes (less than a page) by which to "color" the
- starting stack address of new threads. This number is multiplied by the
- number of threads created so far and then truncated modulo page size,
- to get a roughly even distribution of values for different threads. */
-#define COLORING_INCREMENT 0
-
/* This is a number of bytes that is an alignment that should be avoided
when choosing the exact size of a new thread's stack. If the size
chosen is aligned to this, an extra page will be added to render the
diff --git a/sysdeps/i386/i686/stack-aliasing.h b/sysdeps/i386/i686/stack-aliasing.h
index 1e35ceb2061d60f9..d73e45461f928a6a 100644
--- a/sysdeps/i386/i686/stack-aliasing.h
+++ b/sysdeps/i386/i686/stack-aliasing.h
@@ -16,11 +16,6 @@
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
-/* It turns out that stack coloring is in general not good on P4s. Some
- applications will benefit. We will probably have a configuration option
- at some point. To enable coloring, set this to 128. */
-#define COLORING_INCREMENT 0
-
/* What is useful is to avoid the 64k aliasing problem which reliably
happens if all stacks use sizes which are a multiple of 64k. Tell
the stack allocator to disturb this by allocation one more page if