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NPTL: Refactor createthread.c

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This commit is contained in:
Roland McGrath 2014-11-18 11:03:00 -08:00
parent 107a5bf085
commit 32fed10f0f
3 changed files with 240 additions and 169 deletions
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24
ChangeLog
View File

@ -1,3 +1,27 @@
2014-11-18 Roland McGrath <roland@hack.frob.com>
* nptl/createthread.c: Add proper top-line comment.
(do_clone): Folded into ...
(create_thread): ... here. Take new arguments STOPPED_START and
THREAD_RAN. Always set PD->stopped_start to something here. Don't
increment __nptl_threads, do event-reporting logic, do
CHECK_THREAD_SYSINFO, or set THREAD_SELF->header.multiple_threads
here. Set *THREAD_RAN after ARCH_CLONE call succeeds. Don't do any
resource cleanup if sched_setaffinity or sched_setscheduler fails,
just send SIGCANCEL.
* nptl/pthread_create.c: Forward-declare create_thread before
including createthread.c.
(start_thread): Use new macro START_THREAD_DEFN to replace defining
declaration, and new macro START_THREAD_SELF to replace argument.
Remove return statement.
(report_thread_creation): New function.
(__pthread_create_2_1): Use it. Do TD_CREATE reporting,
synchronization logic, and __nptl_nthreads increment here, around
calling create_thread. Do CHECK_THREAD_SYSINFO and initialize
PD->parent_cancelhandling here, before create_thread. When
create_thread fails, do __nptl_nthreads decrement, setxid_futex wake,
__deallocate_stack, and ENOMEM translation here.
2014-11-18 Joseph Myers <joseph@codesourcery.com>
[BZ #17616]

232
nptl/createthread.c
View File

@ -1,4 +1,5 @@
/* Copyright (C) 2002-2014 Free Software Foundation, Inc.
/* Low-level thread creation for NPTL. Linux version.
Copyright (C) 2002-2014 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
@ -28,124 +29,49 @@
#include <arch-fork.h>
#define CLONE_SIGNAL (CLONE_SIGHAND | CLONE_THREAD)
#ifndef ARCH_CLONE
# define ARCH_CLONE __clone
#endif
/* See the comments in pthread_create.c for the requirements for these
two macros and the create_thread function. */
#define START_THREAD_DEFN \
static int __attribute__ ((noreturn)) start_thread (void *arg)
#define START_THREAD_SELF arg
/* pthread_create.c defines this using START_THREAD_DEFN
We need a forward declaration here so we can take its address. */
static int start_thread (void *arg) __attribute__ ((noreturn));
static int
do_clone (struct pthread *pd, const struct pthread_attr *attr,
int clone_flags, int (*fct) (void *), STACK_VARIABLES_PARMS,
int stopped)
create_thread (struct pthread *pd, const struct pthread_attr *attr,
bool stopped_start, STACK_VARIABLES_PARMS, bool *thread_ran)
{
TLS_DEFINE_INIT_TP (tp, pd);
/* Determine whether the newly created threads has to be started
stopped since we have to set the scheduling parameters or set the
affinity. */
if (attr != NULL
&& (__glibc_unlikely (attr->cpuset != NULL)
|| __glibc_unlikely ((attr->flags & ATTR_FLAG_NOTINHERITSCHED) != 0)))
stopped_start = true;
if (__glibc_unlikely (stopped != 0))
pd->stopped_start = stopped_start;
if (__glibc_unlikely (stopped_start))
/* We make sure the thread does not run far by forcing it to get a
lock. We lock it here too so that the new thread cannot continue
until we tell it to. */
lll_lock (pd->lock, LLL_PRIVATE);
/* One more thread. We cannot have the thread do this itself, since it
might exist but not have been scheduled yet by the time we've returned
and need to check the value to behave correctly. We must do it before
creating the thread, in case it does get scheduled first and then
might mistakenly think it was the only thread. In the failure case,
we momentarily store a false value; this doesn't matter because there
is no kosher thing a signal handler interrupting us right here can do
that cares whether the thread count is correct. */
atomic_increment (&__nptl_nthreads);
int rc = ARCH_CLONE (fct, STACK_VARIABLES_ARGS, clone_flags,
pd, &pd->tid, tp, &pd->tid);
if (__glibc_unlikely (rc == -1))
{
atomic_decrement (&__nptl_nthreads); /* Oops, we lied for a second. */
/* Perhaps a thread wants to change the IDs and if waiting
for this stillborn thread. */
if (__builtin_expect (atomic_exchange_acq (&pd->setxid_futex, 0)
== -2, 0))
lll_futex_wake (&pd->setxid_futex, 1, LLL_PRIVATE);
/* Free the resources. */
__deallocate_stack (pd);
/* We have to translate error codes. */
return errno == ENOMEM ? EAGAIN : errno;
}
/* Now we have the possibility to set scheduling parameters etc. */
if (__glibc_unlikely (stopped != 0))
{
INTERNAL_SYSCALL_DECL (err);
int res = 0;
/* Set the affinity mask if necessary. */
if (attr->cpuset != NULL)
{
res = INTERNAL_SYSCALL (sched_setaffinity, err, 3, pd->tid,
attr->cpusetsize, attr->cpuset);
if (__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (res, err)))
{
/* The operation failed. We have to kill the thread. First
send it the cancellation signal. */
INTERNAL_SYSCALL_DECL (err2);
err_out:
(void) INTERNAL_SYSCALL (tgkill, err2, 3,
THREAD_GETMEM (THREAD_SELF, pid),
pd->tid, SIGCANCEL);
/* We do not free the stack here because the canceled thread
itself will do this. */
return (INTERNAL_SYSCALL_ERROR_P (res, err)
? INTERNAL_SYSCALL_ERRNO (res, err)
: 0);
}
}
/* Set the scheduling parameters. */
if ((attr->flags & ATTR_FLAG_NOTINHERITSCHED) != 0)
{
res = INTERNAL_SYSCALL (sched_setscheduler, err, 3, pd->tid,
pd->schedpolicy, &pd->schedparam);
if (__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (res, err)))
goto err_out;
}
}
/* We now have for sure more than one thread. The main thread might
not yet have the flag set. No need to set the global variable
again if this is what we use. */
THREAD_SETMEM (THREAD_SELF, header.multiple_threads, 1);
return 0;
}
static int
create_thread (struct pthread *pd, const struct pthread_attr *attr,
STACK_VARIABLES_PARMS)
{
#if TLS_TCB_AT_TP
assert (pd->header.tcb != NULL);
#endif
/* We rely heavily on various flags the CLONE function understands:
CLONE_VM, CLONE_FS, CLONE_FILES
These flags select semantics with shared address space and
file descriptors according to what POSIX requires.
CLONE_SIGNAL
This flag selects the POSIX signal semantics.
CLONE_SIGHAND, CLONE_THREAD
This flag selects the POSIX signal semantics and various
other kinds of sharing (itimers, POSIX timers, etc.).
CLONE_SETTLS
The sixth parameter to CLONE determines the TLS area for the
@ -165,76 +91,64 @@ create_thread (struct pthread *pd, const struct pthread_attr *attr,
The termination signal is chosen to be zero which means no signal
is sent. */
int clone_flags = (CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGNAL
| CLONE_SETTLS | CLONE_PARENT_SETTID
| CLONE_CHILD_CLEARTID | CLONE_SYSVSEM
| 0);
const int clone_flags = (CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SYSVSEM
| CLONE_SIGHAND | CLONE_THREAD
| CLONE_SETTLS | CLONE_PARENT_SETTID
| CLONE_CHILD_CLEARTID
| 0);
if (__glibc_unlikely (THREAD_GETMEM (THREAD_SELF, report_events)))
TLS_DEFINE_INIT_TP (tp, pd);
if (__glibc_unlikely (ARCH_CLONE (&start_thread, STACK_VARIABLES_ARGS,
clone_flags, pd, &pd->tid, tp, &pd->tid)
== -1))
return errno;
/* It's started now, so if we fail below, we'll have to cancel it
and let it clean itself up. */
*thread_ran = true;
/* Now we have the possibility to set scheduling parameters etc. */
if (attr != NULL)
{
/* The parent thread is supposed to report events. Check whether
the TD_CREATE event is needed, too. */
const int _idx = __td_eventword (TD_CREATE);
const uint32_t _mask = __td_eventmask (TD_CREATE);
INTERNAL_SYSCALL_DECL (err);
int res;
if ((_mask & (__nptl_threads_events.event_bits[_idx]
| pd->eventbuf.eventmask.event_bits[_idx])) != 0)
/* Set the affinity mask if necessary. */
if (attr->cpuset != NULL)
{
/* We always must have the thread start stopped. */
pd->stopped_start = true;
assert (stopped_start);
/* Create the thread. We always create the thread stopped
so that it does not get far before we tell the debugger. */
int res = do_clone (pd, attr, clone_flags, start_thread,
STACK_VARIABLES_ARGS, 1);
if (res == 0)
res = INTERNAL_SYSCALL (sched_setaffinity, err, 3, pd->tid,
attr->cpusetsize, attr->cpuset);
if (__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (res, err)))
err_out:
{
/* Now fill in the information about the new thread in
the newly created thread's data structure. We cannot let
the new thread do this since we don't know whether it was
already scheduled when we send the event. */
pd->eventbuf.eventnum = TD_CREATE;
pd->eventbuf.eventdata = pd;
/* The operation failed. We have to kill the thread.
We let the normal cancellation mechanism do the work. */
/* Enqueue the descriptor. */
do
pd->nextevent = __nptl_last_event;
while (atomic_compare_and_exchange_bool_acq (&__nptl_last_event,
pd, pd->nextevent)
!= 0);
INTERNAL_SYSCALL_DECL (err2);
(void) INTERNAL_SYSCALL (tgkill, err2, 3,
THREAD_GETMEM (THREAD_SELF, pid),
pd->tid, SIGCANCEL);
/* Now call the function which signals the event. */
__nptl_create_event ();
/* And finally restart the new thread. */
lll_unlock (pd->lock, LLL_PRIVATE);
return INTERNAL_SYSCALL_ERRNO (res, err);
}
}
return res;
/* Set the scheduling parameters. */
if ((attr->flags & ATTR_FLAG_NOTINHERITSCHED) != 0)
{
assert (stopped_start);
res = INTERNAL_SYSCALL (sched_setscheduler, err, 3, pd->tid,
pd->schedpolicy, &pd->schedparam);
if (__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (res, err)))
goto err_out;
}
}
#ifdef NEED_DL_SYSINFO
CHECK_THREAD_SYSINFO (pd);
#endif
/* Determine whether the newly created threads has to be started
stopped since we have to set the scheduling parameters or set the
affinity. */
bool stopped = false;
if (attr != NULL && (attr->cpuset != NULL
|| (attr->flags & ATTR_FLAG_NOTINHERITSCHED) != 0))
stopped = true;
pd->stopped_start = stopped;
pd->parent_cancelhandling = THREAD_GETMEM (THREAD_SELF, cancelhandling);
/* Actually create the thread. */
int res = do_clone (pd, attr, clone_flags, start_thread,
STACK_VARIABLES_ARGS, stopped);
if (res == 0 && stopped)
/* And finally restart the new thread. */
lll_unlock (pd->lock, LLL_PRIVATE);
return res;
return 0;
}

153
nptl/pthread_create.c
View File

@ -36,10 +36,6 @@
#include <stap-probe.h>
/* Local function to start thread and handle cleanup. */
static int start_thread (void *arg);
/* Nozero if debugging mode is enabled. */
int __pthread_debug;
@ -56,7 +52,27 @@ unsigned int __nptl_nthreads = 1;
/* Code to allocate and deallocate a stack. */
#include "allocatestack.c"
/* Code to create the thread. */
/* createthread.c defines this function, and two macros:
START_THREAD_DEFN and START_THREAD_SELF (see below).
create_thread is obliged to initialize PD->stopped_start. It
should be true if the STOPPED_START parameter is true, or if
create_thread needs the new thread to synchronize at startup for
some other implementation reason. If PD->stopped_start will be
true, then create_thread is obliged to perform the operation
"lll_lock (PD->lock, LLL_PRIVATE)" before starting the thread.
The return value is zero for success or an errno code for failure.
If the return value is ENOMEM, that will be translated to EAGAIN,
so create_thread need not do that. On failure, *THREAD_RAN should
be set to true iff the thread actually started up and then got
cancelled before calling user code (*PD->start_routine), in which
case it is responsible for doing its own cleanup. */
static int create_thread (struct pthread *pd, const struct pthread_attr *attr,
bool stopped_start, STACK_VARIABLES_PARMS,
bool *thread_ran);
#include <createthread.c>
@ -228,10 +244,14 @@ __free_tcb (struct pthread *pd)
}
static int
start_thread (void *arg)
/* Local function to start thread and handle cleanup.
createthread.c defines the macro START_THREAD_DEFN to the
declaration that its create_thread function will refer to, and
START_THREAD_SELF to the expression to optimally deliver the new
thread's THREAD_SELF value. */
START_THREAD_DEFN
{
struct pthread *pd = (struct pthread *) arg;
struct pthread *pd = START_THREAD_SELF;
#if HP_TIMING_AVAIL
/* Remember the time when the thread was started. */
@ -439,7 +459,24 @@ start_thread (void *arg)
__exit_thread ();
/* NOTREACHED */
return 0;
}
/* Return true iff obliged to report TD_CREATE events. */
static bool
report_thread_creation (struct pthread *pd)
{
if (__glibc_unlikely (THREAD_GETMEM (THREAD_SELF, report_events)))
{
/* The parent thread is supposed to report events.
Check whether the TD_CREATE event is needed, too. */
const size_t idx = __td_eventword (TD_CREATE);
const uint32_t mask = __td_eventmask (TD_CREATE);
return ((mask & (__nptl_threads_events.event_bits[idx]
| pd->eventbuf.eventmask.event_bits[idx])) != 0);
}
return false;
}
@ -543,6 +580,15 @@ __pthread_create_2_1 (newthread, attr, start_routine, arg)
THREAD_COPY_POINTER_GUARD (pd);
#endif
/* Verify the sysinfo bits were copied in allocate_stack if needed. */
#ifdef NEED_DL_SYSINFO
CHECK_THREAD_SYSINFO (pd);
#endif
/* Inform start_thread (above) about cancellation state that might
translate into inherited signal state. */
pd->parent_cancelhandling = THREAD_GETMEM (THREAD_SELF, cancelhandling);
/* Determine scheduling parameters for the thread. */
if (__builtin_expect ((iattr->flags & ATTR_FLAG_NOTINHERITSCHED) != 0, 0)
&& (iattr->flags & (ATTR_FLAG_SCHED_SET | ATTR_FLAG_POLICY_SET)) != 0)
@ -593,8 +639,95 @@ __pthread_create_2_1 (newthread, attr, start_routine, arg)
LIBC_PROBE (pthread_create, 4, newthread, attr, start_routine, arg);
/* One more thread. We cannot have the thread do this itself, since it
might exist but not have been scheduled yet by the time we've returned
and need to check the value to behave correctly. We must do it before
creating the thread, in case it does get scheduled first and then
might mistakenly think it was the only thread. In the failure case,
we momentarily store a false value; this doesn't matter because there
is no kosher thing a signal handler interrupting us right here can do
that cares whether the thread count is correct. */
atomic_increment (&__nptl_nthreads);
bool thread_ran = false;
/* Start the thread. */
retval = create_thread (pd, iattr, STACK_VARIABLES_ARGS);
if (__glibc_unlikely (report_thread_creation (pd)))
{
/* Create the thread. We always create the thread stopped
so that it does not get far before we tell the debugger. */
retval = create_thread (pd, iattr, true, STACK_VARIABLES_ARGS,
&thread_ran);
if (retval == 0)
{
/* create_thread should have set this so that the logic below can
test it. */
assert (pd->stopped_start);
/* Now fill in the information about the new thread in
the newly created thread's data structure. We cannot let
the new thread do this since we don't know whether it was
already scheduled when we send the event. */
pd->eventbuf.eventnum = TD_CREATE;
pd->eventbuf.eventdata = pd;
/* Enqueue the descriptor. */
do
pd->nextevent = __nptl_last_event;
while (atomic_compare_and_exchange_bool_acq (&__nptl_last_event,
pd, pd->nextevent)
!= 0);
/* Now call the function which signals the event. */
__nptl_create_event ();
}
}
else
retval = create_thread (pd, iattr, false, STACK_VARIABLES_ARGS,
&thread_ran);
if (__glibc_unlikely (retval != 0))
{
/* If thread creation "failed", that might mean that the thread got
created and ran a little--short of running user code--but then
create_thread cancelled it. In that case, the thread will do all
its own cleanup just like a normal thread exit after a successful
creation would do. */
if (thread_ran)
assert (pd->stopped_start);
else
{
/* Oops, we lied for a second. */
atomic_decrement (&__nptl_nthreads);
/* Perhaps a thread wants to change the IDs and is waiting for this
stillborn thread. */
if (__glibc_unlikely (atomic_exchange_acq (&pd->setxid_futex, 0)
== -2))
lll_futex_wake (&pd->setxid_futex, 1, LLL_PRIVATE);
/* Free the resources. */
__deallocate_stack (pd);
}
/* We have to translate error codes. */
if (retval == ENOMEM)
retval = EAGAIN;
}
else
{
if (pd->stopped_start)
/* The thread blocked on this lock either because we're doing TD_CREATE
event reporting, or for some other reason that create_thread chose.
Now let it run free. */
lll_unlock (pd->lock, LLL_PRIVATE);
/* We now have for sure more than one thread. The main thread might
not yet have the flag set. No need to set the global variable
again if this is what we use. */
THREAD_SETMEM (THREAD_SELF, header.multiple_threads, 1);
}
out:
if (__glibc_unlikely (free_cpuset))