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Add and use new glibc-internal futex API.

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This adds new functions for futex operations, starting with wait,
abstimed_wait, reltimed_wait, wake.  They add documentation and error
checking according to the current draft of the Linux kernel futex manpage.

Waiting with absolute or relative timeouts is split into separate functions.
This allows for removing a few cases of code duplication in pthreads code,
which uses absolute timeouts; also, it allows us to put platform-specific
code to go from an absolute to a relative timeout into the platform-specific
futex abstractions..

Futex operations that can be canceled are also split out into separate
functions suffixed by "_cancelable".

There are separate versions for both Linux and NaCl; while they currently
differ only slightly, my expectation is that the separate versions of
lowlevellock-futex.h will eventually be merged into futex-internal.h
when we get to move the lll_ functions over to the new futex API.
This commit is contained in:
Torvald Riegel
2014-12-04 14:12:23 +01:00
parent 203c1a898d
commit a2f0363f81
40 changed files with 963 additions and 492 deletions
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14
nptl/pthread_create.c
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@@ -31,6 +31,7 @@
#include <kernel-features.h>
#include <exit-thread.h>
#include <default-sched.h>
#include <futex-internal.h>
#include <shlib-compat.h>
@@ -269,7 +270,7 @@ START_THREAD_DEFN
/* Allow setxid from now onwards. */
if (__glibc_unlikely (atomic_exchange_acq (&pd->setxid_futex, 0) == -2))
lll_futex_wake (&pd->setxid_futex, 1, LLL_PRIVATE);
futex_wake (&pd->setxid_futex, 1, FUTEX_PRIVATE);
#ifdef __NR_set_robust_list
# ifndef __ASSUME_SET_ROBUST_LIST
@@ -414,7 +415,8 @@ START_THREAD_DEFN
this->__list.__next = NULL;
atomic_or (&this->__lock, FUTEX_OWNER_DIED);
lll_futex_wake (&this->__lock, 1, /* XYZ */ LLL_SHARED);
futex_wake ((unsigned int *) &this->__lock, 1,
/* XYZ */ FUTEX_SHARED);
}
while (robust != (void *) &pd->robust_head);
}
@@ -442,7 +444,11 @@ START_THREAD_DEFN
/* Some other thread might call any of the setXid functions and expect
us to reply. In this case wait until we did that. */
do
lll_futex_wait (&pd->setxid_futex, 0, LLL_PRIVATE);
/* XXX This differs from the typical futex_wait_simple pattern in that
the futex_wait condition (setxid_futex) is different from the
condition used in the surrounding loop (cancelhandling). We need
to check and document why this is correct. */
futex_wait_simple (&pd->setxid_futex, 0, FUTEX_PRIVATE);
while (pd->cancelhandling & SETXID_BITMASK);
/* Reset the value so that the stack can be reused. */
@@ -683,7 +689,7 @@ __pthread_create_2_1 (newthread, attr, start_routine, arg)
stillborn thread. */
if (__glibc_unlikely (atomic_exchange_acq (&pd->setxid_futex, 0)
== -2))
lll_futex_wake (&pd->setxid_futex, 1, LLL_PRIVATE);
futex_wake (&pd->setxid_futex, 1, FUTEX_PRIVATE);
/* Free the resources. */
__deallocate_stack (pd);