diff options
| -rw-r--r-- | ChangeLog | 24 | ||||
| -rw-r--r-- | nptl/createthread.c | 232 | ||||
| -rw-r--r-- | nptl/pthread_create.c | 153 |
3 files changed, 240 insertions, 169 deletions
@@ -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] diff --git a/nptl/createthread.c b/nptl/createthread.c index 49442d9..7b05d48 100644 --- a/nptl/createthread.c +++ b/nptl/createthread.c @@ -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. @@ -28,91 +29,119 @@ #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); + /* We rely heavily on various flags the CLONE function understands: - int rc = ARCH_CLONE (fct, STACK_VARIABLES_ARGS, clone_flags, - pd, &pd->tid, tp, &pd->tid); + CLONE_VM, CLONE_FS, CLONE_FILES + These flags select semantics with shared address space and + file descriptors according to what POSIX requires. - if (__glibc_unlikely (rc == -1)) - { - atomic_decrement (&__nptl_nthreads); /* Oops, we lied for a second. */ + CLONE_SIGHAND, CLONE_THREAD + This flag selects the POSIX signal semantics and various + other kinds of sharing (itimers, POSIX timers, etc.). - /* 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); + CLONE_SETTLS + The sixth parameter to CLONE determines the TLS area for the + new thread. - /* Free the resources. */ - __deallocate_stack (pd); + CLONE_PARENT_SETTID + The kernels writes the thread ID of the newly created thread + into the location pointed to by the fifth parameters to CLONE. - /* We have to translate error codes. */ - return errno == ENOMEM ? EAGAIN : errno; - } + Note that it would be semantically equivalent to use + CLONE_CHILD_SETTID but it is be more expensive in the kernel. + + CLONE_CHILD_CLEARTID + The kernels clears the thread ID of a thread that has called + sys_exit() in the location pointed to by the seventh parameter + to CLONE. + + The termination signal is chosen to be zero which means no signal + is sent. */ + 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); + + 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 (__glibc_unlikely (stopped != 0)) + if (attr != NULL) { INTERNAL_SYSCALL_DECL (err); - int res = 0; + int res; /* Set the affinity mask if necessary. */ if (attr->cpuset != NULL) { + assert (stopped_start); + res = INTERNAL_SYSCALL (sched_setaffinity, err, 3, pd->tid, attr->cpusetsize, attr->cpuset); if (__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (res, err))) + err_out: { - /* The operation failed. We have to kill the thread. First - send it the cancellation signal. */ + /* The operation failed. We have to kill the thread. + We let the normal cancellation mechanism do the work. */ + 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); + return INTERNAL_SYSCALL_ERRNO (res, err); } } /* 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); @@ -121,120 +150,5 @@ do_clone (struct pthread *pd, const struct pthread_attr *attr, } } - /* 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_SETTLS - The sixth parameter to CLONE determines the TLS area for the - new thread. - - CLONE_PARENT_SETTID - The kernels writes the thread ID of the newly created thread - into the location pointed to by the fifth parameters to CLONE. - - Note that it would be semantically equivalent to use - CLONE_CHILD_SETTID but it is be more expensive in the kernel. - - CLONE_CHILD_CLEARTID - The kernels clears the thread ID of a thread that has called - sys_exit() in the location pointed to by the seventh parameter - to CLONE. - - 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); - - 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 int _idx = __td_eventword (TD_CREATE); - const uint32_t _mask = __td_eventmask (TD_CREATE); - - if ((_mask & (__nptl_threads_events.event_bits[_idx] - | pd->eventbuf.eventmask.event_bits[_idx])) != 0) - { - /* We always must have the thread start stopped. */ - pd->stopped_start = true; - - /* 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) - { - /* 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 (); - - /* And finally restart the new thread. */ - lll_unlock (pd->lock, LLL_PRIVATE); - } - - return res; - } - } - -#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; -} diff --git a/nptl/pthread_create.c b/nptl/pthread_create.c index 0055634..da3dc46 100644 --- a/nptl/pthread_create.c +++ b/nptl/pthread_create.c @@ -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)) |