Re: [PATCH 2/3] Remove __ASSUME_SET_ROBUST_LIST

[Adhemerval Zanella <adhemerval dot zanella at linaro dot org>]

Ping.

On 18/05/2016 18:57, Adhemerval Zanella wrote:
> This patch removes __ASSUME_SET_ROBUST_LIST usage and assumes that
> kernel will correctly return if it supports or not
> futex_atomic_cmpxchg_inatomic.
> 
> On minimum supported kernel (v3.2 and v2.6.32 for x86) kernel has:
> 
> 2418 SYSCALL_DEFINE2(set_robust_list, struct robust_list_head __user *, head,
> 2419                 size_t, len)
> 2420 {
> 2421         if (!futex_cmpxchg_enabled)
> 2422                 return -ENOSYS;
> 
> The patch also adds the __set_robust_list_avail runtime check for all
> architectures, since for some the syscall may still return ENOSYS if
> futex_atomic_cmpxchg_inatomic is not supported (for instance ARM).
> 
> Tested on armhf (with 3.8 kernel) and x86_64.
> 
> 	* nptl/nptl-init.c [__ASSUME_SET_ROBUST_LIST]
> 	(__set_robust_list_avail): Remove define.
> 	[__NR_set_robust_list] (__pthread_initialize_minimal_internal):
> 	Likewise.
> 	* nptl/pthreadP.h [__ASSUME_SET_ROBUST_LIST]
> 	(__set_robust_list_avail): Likewise.
> 	* nptl/pthread_create.c
> 	[__NR_set_robust_list && !__ASSUME_SET_ROBUST_LIST]
> 	(START_THREAD_DEFN): Likewise.
> 	* nptl/pthread_mutex_init.c [!__ASSUME_SET_ROBUST_LIST]
> 	(__pthread_mutex_init): Likewise.
> 	* sysdeps/unix/sysv/linux/arm/kernel-features.h
> 	(__ASSUME_SET_ROBUST_LIST): Likewise.
> 	* sysdeps/unix/sysv/linux/kernel-features.h:
> 	(__ASSUME_SET_ROBUST_LIST): Likewise.
> 	* sysdeps/unix/sysv/linux/m68k/kernel-features.h:
> 	(__ASSUME_SET_ROBUST_LIST): Likewise.
> 	* sysdeps/unix/sysv/linux/mips/kernel-features.h:
> 	(__ASSUME_SET_ROBUST_LIST): Likewise.
> 	* sysdeps/unix/sysv/linux/sparc/kernel-features.h:
> 	(__ASSUME_SET_ROBUST_LIST): Likewise.
> ---
>  ChangeLog                                       | 22 ++++++++++++++++++++++
>  nptl/nptl-init.c                                | 11 ++---------
>  nptl/pthreadP.h                                 |  2 --
>  nptl/pthread_create.c                           |  8 +-------
>  nptl/pthread_mutex_init.c                       |  2 --
>  sysdeps/unix/sysv/linux/arm/kernel-features.h   |  1 -
>  sysdeps/unix/sysv/linux/kernel-features.h       |  5 -----
>  sysdeps/unix/sysv/linux/m68k/kernel-features.h  |  1 -
>  sysdeps/unix/sysv/linux/mips/kernel-features.h  |  1 -
>  sysdeps/unix/sysv/linux/sparc/kernel-features.h |  1 -
>  10 files changed, 25 insertions(+), 29 deletions(-)
> 
> diff --git a/nptl/nptl-init.c b/nptl/nptl-init.c
> index bdbdfed..cad14c7 100644
> --- a/nptl/nptl-init.c
> +++ b/nptl/nptl-init.c
> @@ -48,14 +48,8 @@ int *__libc_multiple_threads_ptr attribute_hidden;
>  size_t __static_tls_size;
>  size_t __static_tls_align_m1;
>  
> -#ifndef __ASSUME_SET_ROBUST_LIST
>  /* Negative if we do not have the system call and we can use it.  */
>  int __set_robust_list_avail;
> -# define set_robust_list_not_avail() \
> -  __set_robust_list_avail = -1
> -#else
> -# define set_robust_list_not_avail() do { } while (0)
> -#endif
>  
>  #ifndef __ASSUME_FUTEX_CLOCK_REALTIME
>  /* Nonzero if we do not have FUTEX_CLOCK_REALTIME.  */
> @@ -328,7 +322,7 @@ __pthread_initialize_minimal_internal (void)
>      pd->robust_prev = &pd->robust_head;
>  #endif
>      pd->robust_head.list = &pd->robust_head;
> -#ifdef __NR_set_robust_list
> +
>      pd->robust_head.futex_offset = (offsetof (pthread_mutex_t, __data.__lock)
>  				    - offsetof (pthread_mutex_t,
>  						__data.__list.__next));
> @@ -336,8 +330,7 @@ __pthread_initialize_minimal_internal (void)
>      int res = INTERNAL_SYSCALL (set_robust_list, err, 2, &pd->robust_head,
>  				sizeof (struct robust_list_head));
>      if (INTERNAL_SYSCALL_ERROR_P (res, err))
> -#endif
> -      set_robust_list_not_avail ();
> +      __set_robust_list_avail = -1;
>    }
>  
>  #ifdef __NR_futex
> diff --git a/nptl/pthreadP.h b/nptl/pthreadP.h
> index 4edc74b..d479a3e 100644
> --- a/nptl/pthreadP.h
> +++ b/nptl/pthreadP.h
> @@ -199,10 +199,8 @@ hidden_proto (__pthread_keys)
>  /* Number of threads running.  */
>  extern unsigned int __nptl_nthreads attribute_hidden;
>  
> -#ifndef __ASSUME_SET_ROBUST_LIST
>  /* Negative if we do not have the system call and we can use it.  */
>  extern int __set_robust_list_avail attribute_hidden;
> -#endif
>  
>  /* Thread Priority Protection.  */
>  extern int __sched_fifo_min_prio attribute_hidden;
> diff --git a/nptl/pthread_create.c b/nptl/pthread_create.c
> index a834063..c3f4087 100644
> --- a/nptl/pthread_create.c
> +++ b/nptl/pthread_create.c
> @@ -271,10 +271,7 @@ START_THREAD_DEFN
>    if (__glibc_unlikely (atomic_exchange_acq (&pd->setxid_futex, 0) == -2))
>      futex_wake (&pd->setxid_futex, 1, FUTEX_PRIVATE);
>  
> -#ifdef __NR_set_robust_list
> -# ifndef __ASSUME_SET_ROBUST_LIST
> -  if (__set_robust_list_avail >= 0)
> -# endif
> +  if (__glibc_likely (__set_robust_list_avail >= 0))
>      {
>        INTERNAL_SYSCALL_DECL (err);
>        /* This call should never fail because the initial call in init.c
> @@ -282,7 +279,6 @@ START_THREAD_DEFN
>        INTERNAL_SYSCALL (set_robust_list, err, 2, &pd->robust_head,
>  			sizeof (struct robust_list_head));
>      }
> -#endif
>  
>  #ifdef SIGCANCEL
>    /* If the parent was running cancellation handlers while creating
> @@ -388,7 +384,6 @@ START_THREAD_DEFN
>       the breakpoint reports TD_THR_RUN state rather than TD_THR_ZOMBIE.  */
>    atomic_bit_set (&pd->cancelhandling, EXITING_BIT);
>  
> -#ifndef __ASSUME_SET_ROBUST_LIST
>    /* If this thread has any robust mutexes locked, handle them now.  */
>  # ifdef __PTHREAD_MUTEX_HAVE_PREV
>    void *robust = pd->robust_head.list;
> @@ -419,7 +414,6 @@ START_THREAD_DEFN
>  	}
>        while (robust != (void *) &pd->robust_head);
>      }
> -#endif
>  
>    /* Mark the memory of the stack as usable to the kernel.  We free
>       everything except for the space used for the TCB itself.  */
> diff --git a/nptl/pthread_mutex_init.c b/nptl/pthread_mutex_init.c
> index 6e5acb6..6aef890 100644
> --- a/nptl/pthread_mutex_init.c
> +++ b/nptl/pthread_mutex_init.c
> @@ -91,11 +91,9 @@ __pthread_mutex_init (pthread_mutex_t *mutex,
>  
>    if ((imutexattr->mutexkind & PTHREAD_MUTEXATTR_FLAG_ROBUST) != 0)
>      {
> -#ifndef __ASSUME_SET_ROBUST_LIST
>        if ((imutexattr->mutexkind & PTHREAD_MUTEXATTR_FLAG_PSHARED) != 0
>  	  && __set_robust_list_avail < 0)
>  	return ENOTSUP;
> -#endif
>  
>        mutex->__data.__kind |= PTHREAD_MUTEX_ROBUST_NORMAL_NP;
>      }
> diff --git a/sysdeps/unix/sysv/linux/arm/kernel-features.h b/sysdeps/unix/sysv/linux/arm/kernel-features.h
> index 6ca607e..4012751 100644
> --- a/sysdeps/unix/sysv/linux/arm/kernel-features.h
> +++ b/sysdeps/unix/sysv/linux/arm/kernel-features.h
> @@ -24,7 +24,6 @@
>     configuration.  */
>  #if __LINUX_KERNEL_VERSION < 0x030E03
>  # undef __ASSUME_REQUEUE_PI
> -# undef __ASSUME_SET_ROBUST_LIST
>  #endif
>  
>  /* Define this if your 32-bit syscall API requires 64-bit register
> diff --git a/sysdeps/unix/sysv/linux/kernel-features.h b/sysdeps/unix/sysv/linux/kernel-features.h
> index 43b72b1..45edad5 100644
> --- a/sysdeps/unix/sysv/linux/kernel-features.h
> +++ b/sysdeps/unix/sysv/linux/kernel-features.h
> @@ -59,11 +59,6 @@
>     they were introduced in 2.6.17-rc1, on SH in 2.6.19-rc1.  */
>  #define __ASSUME_ATFCTS	1
>  
> -/* Support for inter-process robust mutexes was added in 2.6.17 (but
> -   some architectures lack futex_atomic_cmpxchg_inatomic in some
> -   configurations).  */
> -#define __ASSUME_SET_ROBUST_LIST	1
> -
>  /* Support for private futexes was added in 2.6.22.  */
>  #define __ASSUME_PRIVATE_FUTEX	1
>  
> diff --git a/sysdeps/unix/sysv/linux/m68k/kernel-features.h b/sysdeps/unix/sysv/linux/m68k/kernel-features.h
> index 9e7f0e1..bec9539 100644
> --- a/sysdeps/unix/sysv/linux/m68k/kernel-features.h
> +++ b/sysdeps/unix/sysv/linux/m68k/kernel-features.h
> @@ -52,5 +52,4 @@
>  /* No support for PI futexes or robust mutexes before 3.10 for m68k.  */
>  #if __LINUX_KERNEL_VERSION < 0x030a00
>  # undef __ASSUME_REQUEUE_PI
> -# undef __ASSUME_SET_ROBUST_LIST
>  #endif
> diff --git a/sysdeps/unix/sysv/linux/mips/kernel-features.h b/sysdeps/unix/sysv/linux/mips/kernel-features.h
> index 09d5ece..3640b5f 100644
> --- a/sysdeps/unix/sysv/linux/mips/kernel-features.h
> +++ b/sysdeps/unix/sysv/linux/mips/kernel-features.h
> @@ -25,7 +25,6 @@
>     emulating LL/SC.  */
>  #if __mips == 1 || defined _MIPS_ARCH_R5900
>  # undef __ASSUME_REQUEUE_PI
> -# undef __ASSUME_SET_ROBUST_LIST
>  #endif
>  
>  /* Define this if your 32-bit syscall API requires 64-bit register
> diff --git a/sysdeps/unix/sysv/linux/sparc/kernel-features.h b/sysdeps/unix/sysv/linux/sparc/kernel-features.h
> index 69c9c7c..dc7c4aa 100644
> --- a/sysdeps/unix/sysv/linux/sparc/kernel-features.h
> +++ b/sysdeps/unix/sysv/linux/sparc/kernel-features.h
> @@ -35,5 +35,4 @@
>     futex_atomic_cmpxchg_inatomic.  */
>  #if !defined __arch64__ && !defined __sparc_v9__
>  # undef __ASSUME_REQUEUE_PI
> -# undef __ASSUME_SET_ROBUST_LIST
>  #endif
>