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drd/Linux: eliminate busy waiting when starting a thread

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git-svn-id: svn://svn.valgrind.org/valgrind/trunk@11920
This commit is contained in:
Bart Van Assche 2011-07-26 19:30:28 +00:00
parent 9066a0acab
commit 39b5365cd9
1 changed files with 50 additions and 6 deletions
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56
drd/drd_pthread_intercepts.c
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@ -55,6 +55,10 @@
#include <stdio.h> /* fprintf() */
#include <stdlib.h> /* malloc(), free() */
#include <unistd.h> /* confstr() */
#ifdef __linux__
#include <asm/unistd.h> /* __NR_futex */
#include <linux/futex.h> /* FUTEX_WAIT */
#endif
#include "config.h" /* HAVE_PTHREAD_MUTEX_ADAPTIVE_NP etc. */
#include "drd_basics.h" /* DRD_() */
#include "drd_clientreq.h"
@ -129,12 +133,16 @@ static int never_true;
/* Local data structures. */
typedef struct {
volatile int counter;
} DrdSema;
typedef struct
{
void* (*start)(void*);
void* arg;
int detachstate;
int wrapper_started;
DrdSema wrapper_started;
} DrdPosixThreadArgs;
@ -143,6 +151,10 @@ typedef struct
static void DRD_(init)(void) __attribute__((constructor));
static void DRD_(check_threading_library)(void);
static void DRD_(set_main_thread_state)(void);
static void DRD_(sema_init)(DrdSema* sema);
static void DRD_(sema_destroy)(DrdSema* sema);
static void DRD_(sema_down)(DrdSema* sema);
static void DRD_(sema_up)(DrdSema* sema);
/* Function definitions. */
@ -163,6 +175,38 @@ static void DRD_(init)(void)
DRD_(set_main_thread_state)();
}
static void DRD_(sema_init)(DrdSema* sema)
{
DRD_IGNORE_VAR(sema->counter);
sema->counter = 0;
}
static void DRD_(sema_destroy)(DrdSema* sema)
{
}
static void DRD_(sema_down)(DrdSema* sema)
{
while (sema->counter == 0) {
#ifdef __linux__
syscall(__NR_futex, (UWord)&sema->counter,
FUTEX_WAIT | FUTEX_PRIVATE_FLAG, 0);
#else
sched_yield();
#endif
}
sema->counter--;
}
static void DRD_(sema_up)(DrdSema* sema)
{
sema->counter++;
#ifdef __linux__
syscall(__NR_futex, (UWord)&sema->counter,
FUTEX_WAKE | FUTEX_PRIVATE_FLAG, 1);
#endif
}
/**
* POSIX threads and DRD each have their own mutex type identification.
* Convert POSIX threads' mutex type to DRD's mutex type. In the code below
@ -277,7 +321,7 @@ static void* DRD_(thread_wrapper)(void* arg)
* DRD_(set_joinable)() have been invoked to avoid a race with
* a pthread_detach() invocation for this thread from another thread.
*/
arg_ptr->wrapper_started = 1;
DRD_(sema_up)(&arg_ptr->wrapper_started);
return (arg_copy.start)(arg_copy.arg);
}
@ -379,8 +423,7 @@ int pthread_create_intercept(pthread_t* thread, const pthread_attr_t* attr,
thread_args.start = start;
thread_args.arg = arg;
DRD_IGNORE_VAR(thread_args.wrapper_started);
thread_args.wrapper_started = 0;
DRD_(sema_init)(&thread_args.wrapper_started);
/*
* Find out whether the thread will be started as a joinable thread
* or as a detached thread. If no thread attributes have been specified,
@ -402,10 +445,11 @@ int pthread_create_intercept(pthread_t* thread, const pthread_attr_t* attr,
if (ret == 0)
{
/* Wait until the thread wrapper started. */
while (!thread_args.wrapper_started)
sched_yield();
DRD_(sema_down)(&thread_args.wrapper_started);
}
DRD_(sema_destroy)(&thread_args.wrapper_started);
VALGRIND_DO_CLIENT_REQUEST_EXPR(-1, VG_USERREQ__DRD_START_NEW_SEGMENT,
pthread_self(), 0, 0, 0, 0);