Re: [PATCH] Use inline syscalls for non-cancellable versions

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

On issue I found for this patchset is it fails for tile (and it is the
only architecture I found that this warning shows) with:

--

malloc.c: In function ‘_int_free’:
../sysdeps/unix/sysv/linux/malloc-sysdep.h:51:35: error: ‘val’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
    may_shrink_heap = n > 0 && val == '2';
                                   ^
../sysdeps/unix/sysv/linux/malloc-sysdep.h:49:9: note: ‘val’ was declared here
    char val;

--

It is due the fact 'read_not_cancel' now calls the INLINE_SYSCALL for the
architecture and so 'tile' version is triggering this issue for some reason
(I did not check exactly why, any tile expert could help me out here?).

The straightforward fix would just initialize this variable, but this is
just clobbering tile potential issue.  Any recommendations? 

On 20-05-2015 11:19, Adhemerval Zanella wrote:
> Hi
> 
> This patch is one of the required adjustments for the fix for bz12683
> (Race conditions in pthread cancellation) and the idea is to not rely
> on the non-cancelable entry points for cancelable syscalls (since the
> upcoming fill will remove them).
>  
> This patch uses inline calls (through INLINE_SYSCALL macro) to define
> the non-cancellable functions macros to avoid use of the
> syscall_nocancel entrypoint.
> 
> Tested on i386, x86_64, x32, powerpc32, powerpc64, arm, and aarch64.
> 
> ---
> 
> 	* sysdeps/unix/sysv/linux/not-cancel.h (open_not_cancel): Rewrite to
> 	be an inline implementation regardless of library is built within.
> 	(open_not_cancel_2): Likewise.
> 	(__read_nocancel): Likewise.
> 	(__write_nocancel): Likewise.
> 	(openat_not_cancel): Likewise.
> 	(openat_not_cancel_3): Likewise.
> 	(openat64_not_cancel): Likewise.
> 	(openat64_not_cancel_3): Likewise.
> 	(__close_nocancel): Likewise.
> 	(pause_not_cancel): Likewise.
> 	(nanosleep_not_cancel): Likewise.
> 	(sigsuspend_not_cancel): Likewise.
> 
> --
> 
> diff --git a/sysdeps/unix/sysv/linux/not-cancel.h b/sysdeps/unix/sysv/linux/not-cancel.h
> index 62d487f..8a358fd 100644
> --- a/sysdeps/unix/sysv/linux/not-cancel.h
> +++ b/sysdeps/unix/sysv/linux/not-cancel.h
> @@ -17,48 +17,48 @@
>     License along with the GNU C Library; if not, see
>     <http://www.gnu.org/licenses/>.  */
>  
> +#ifndef NOT_CANCEL_H
> +# define NOT_CANCEL_H
> +
>  #include <sysdep.h>
> +#include <errno.h>
> +#include <unistd.h>
> +#include <sys/syscall.h>
>  
> -#if IS_IN (libc) || IS_IN (libpthread) || IS_IN (librt)
> -extern int __open_nocancel (const char *, int, ...) attribute_hidden;
> -extern int __close_nocancel (int) attribute_hidden;
> -extern int __read_nocancel (int, void *, size_t) attribute_hidden;
> -extern int __write_nocancel (int, const void *, size_t) attribute_hidden;
> -extern pid_t __waitpid_nocancel (pid_t, int *, int) attribute_hidden;
> -extern int __openat_nocancel (int fd, const char *fname, int oflag,
> -				mode_t mode) attribute_hidden;
> -extern int __openat64_nocancel (int fd, const char *fname, int oflag,
> -				  mode_t mode) attribute_hidden;
> +/* Uncancelable open.  */
> +#ifdef __NR_open
> +# define open_not_cancel(name, flags, mode) \
> +   INLINE_SYSCALL (open, 3, name, flags, mode)
> +# define open_not_cancel_2(name, flags) \
> +   INLINE_SYSCALL (open, 2, name, flags)
>  #else
> -# define __open_nocancel(name, ...) __open (name, __VA_ARGS__)
> -# define __close_nocancel(fd) __close (fd)
> -# define __read_nocancel(fd, buf, len) __read (fd, buf, len)
> -# define __write_nocancel(fd, buf, len) __write (fd, buf, len)
> -# define __waitpid_nocancel(pid, stat_loc, options) \
> -  __waitpid (pid, stat_loc, options)
> -# define __openat_nocancel(fd, fname, oflag, mode) \
> -  openat (fd, fname, oflag, mode)
> -# define __openat64_nocancel(fd, fname, oflag, mode) \
> -  openat64 (fd, fname, oflag, mode)
> +# define open_not_cancel(name, flags, mode) \
> +   INLINE_SYSCALL (openat, 4, AT_FDCWD, name, flags, mode)
> +# define open_not_cancel_2(name, flags) \
> +   INLINE_SYSCALL (openat, 3, AT_FDCWD, name, flags)
>  #endif
>  
> -/* Uncancelable open.  */
> -#define open_not_cancel(name, flags, mode) \
> -   __open_nocancel (name, flags, mode)
> -#define open_not_cancel_2(name, flags) \
> -   __open_nocancel (name, flags)
> +/* Uncancelable read.  */
> +#define __read_nocancel(fd, buf, len) \
> +  INLINE_SYSCALL (read, 3, fd, buf, len)
> +
> +/* Uncancelable write.  */
> +#define __write_nocancel(fd, buf, len) \
> +  INLINE_SYSCALL (write, 3, fd, buf, len)
>  
>  /* Uncancelable openat.  */
>  #define openat_not_cancel(fd, fname, oflag, mode) \
> -  __openat_nocancel (fd, fname, oflag, mode)
> +  INLINE_SYSCALL (openat, 4, fd, fname, oflag, mode)
>  #define openat_not_cancel_3(fd, fname, oflag) \
> -  __openat_nocancel (fd, fname, oflag, 0)
> +  INLINE_SYSCALL (openat, 3, fd, fname, oflag)
>  #define openat64_not_cancel(fd, fname, oflag, mode) \
> -  __openat64_nocancel (fd, fname, oflag, mode)
> +  INLINE_SYSCALL (openat, 4, fd, fname, oflag | O_LARGEFILE, mode)
>  #define openat64_not_cancel_3(fd, fname, oflag) \
> -  __openat64_nocancel (fd, fname, oflag, 0)
> +  INLINE_SYSCALL (openat, 3, fd, fname, oflag | O_LARGEFILE)
>  
>  /* Uncancelable close.  */
> +#define __close_nocancel(fd) \
> +  INLINE_SYSCALL (close, 1, fd)
>  #define close_not_cancel(fd) \
>    __close_nocancel (fd)
>  #define close_not_cancel_no_status(fd) \
> @@ -83,17 +83,27 @@ extern int __openat64_nocancel (int fd, const char *fname, int oflag,
>    __fcntl_nocancel (fd, cmd, val)
>  
>  /* Uncancelable waitpid.  */
> -#define waitpid_not_cancel(pid, stat_loc, options) \
> +#define __waitpid_nocancel(pid, stat_loc, options) \
>    INLINE_SYSCALL (wait4, 4, pid, stat_loc, options, NULL)
> +#define waitpid_not_cancel(pid, stat_loc, options) \
> +  __waitpid_nocancel(pid, stat_loc, options)
>  
>  /* Uncancelable pause.  */
>  #define pause_not_cancel() \
> -  __pause_nocancel ()
> +  ({ sigset_t set; 							     \
> +     int __rc = INLINE_SYSCALL (rt_sigprocmask, 4, SIG_BLOCK, NULL, &set,    \
> +				_NSIG / 8);				     \
> +     if (__rc == 0)							     \
> +       __rc = INLINE_SYSCALL (rt_sigsuspend, 2, &set, _NSIG / 8);	     \
> +     __rc;								     \
> +  })
>  
>  /* Uncancelable nanosleep.  */
>  #define nanosleep_not_cancel(requested_time, remaining) \
> -  __nanosleep_nocancel (requested_time, remaining)
> +  INLINE_SYSCALL (nanosleep, 2, requested_time, remaining)
>  
>  /* Uncancelable sigsuspend.  */
>  #define sigsuspend_not_cancel(set) \
> -  __sigsuspend_nocancel (set)
> +  INLINE_SYSCALL (rt_sigsuspend, 2, set, _NSIG / 8)
> +
> +#endif /* NOT_CANCEL_H  */
> diff --git a/sysdeps/unix/sysv/linux/powerpc/get_clockfreq.c b/sysdeps/unix/sysv/linux/powerpc/get_clockfreq.c
> index 5b6bb51..3578ea8 100644
> --- a/sysdeps/unix/sysv/linux/powerpc/get_clockfreq.c
> +++ b/sysdeps/unix/sysv/linux/powerpc/get_clockfreq.c
> @@ -41,7 +41,7 @@ __get_clockfreq (void)
>       contains at least one line like:
>       timebase        : 33333333
>       We search for this line and convert the number into an integer.  */
> -  int fd = __open_nocancel ("/proc/cpuinfo", O_RDONLY);
> +  int fd = open_not_cancel_2 ("/proc/cpuinfo", O_RDONLY);
>    if (__glibc_likely (fd != -1))
>      return result;
>