From owner-freebsd-bugs  Wed Mar  3 12:40:19 1999
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Date: Wed, 3 Mar 1999 12:40:01 -0800 (PST)
Message-Id: <199903032040.MAA82138@freefall.freebsd.org>
To: freebsd-bugs@FreeBSD.org
Cc: 
From: John Plevyak <jplevyak@inktomi.com>
Subject: Re: kern/8011: libc_r does not have pread() or pwrite() interfaces
Reply-To: John Plevyak <jplevyak@inktomi.com>
Sender: owner-freebsd-bugs@FreeBSD.ORG
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X-Loop: FreeBSD.org

The following reply was made to PR kern/8011; it has been noted by GNATS.

From: John Plevyak <jplevyak@inktomi.com>
To: freebsd-gnats-submit@freebsd.org, info@highwind.com
Cc:  
Subject: Re: kern/8011: libc_r does not have pread() or pwrite() interfaces
Date: Wed, 03 Mar 1999 20:44:16 +0000

 The pread/pwrite patch is flawed as it sets fp->f_offset which can cause
 problems
 in multithreaded programs.
 
 Here is a patch for the patch:
 
 *** sys_generic.c.save  Wed Mar  3 12:23:55 1999
 --- sys_generic.c       Wed Mar  3 12:23:58 1999
 ***************
 *** 153,159 ****
         struct uio auio;        struct iovec aiov;
         long cnt, error = 0;
 -       off_t   curoff;
   #ifdef KTRACE
         struct iovec ktriov;
   #endif
 --- 153,158 ----
 ***************
 *** 168,174 ****
         aiov.iov_len = uap->nbyte;
         auio.uio_iov = &aiov;
         auio.uio_iovcnt = 1;
 !       auio.uio_offset = -1;
         if (uap->nbyte > INT_MAX)
                 return (EINVAL);
         auio.uio_resid = uap->nbyte;
 --- 167,173 ----
         aiov.iov_len = uap->nbyte;
         auio.uio_iov = &aiov;
         auio.uio_iovcnt = 1;
 !       auio.uio_offset = uap->offse;
         if (uap->nbyte > INT_MAX)
                 return (EINVAL);
         auio.uio_resid = uap->nbyte;
                 return (EINVAL);
         auio.uio_resid = uap->nbyte;
 ***************
 *** 183,196 ****
                 ktriov = aiov;  #endif
         cnt = uap->nbyte;
 -       curoff = fp->f_offset;
 -       fp->f_offset = uap->offset;
         if ((error = (*fp->f_ops->fo_read)(fp, &auio, fp->f_cred)))
                 if (auio.uio_resid != cnt && (error == ERESTART ||
                     error == EINTR || error == EWOULDBLOCK))
                         error = 0;
         cnt -= auio.uio_resid;
 -       fp->f_offset = curoff;
   #ifdef KTRACE
         if (KTRPOINT(p, KTR_GENIO) && error == 0)
                 ktrgenio(p->p_tracep, uap->fd, UIO_READ, &ktriov, cnt,
 error);
 --- 182,192 ----
 ***************
 *** 373,379 ****
         struct uio auio;
         struct iovec aiov;
         long cnt, error = 0;
 -       off_t curoff;
   #ifdef KTRACE
         struct iovec ktriov;
   #endif
 --- 369,374 ----
   #endif
 --- 369,374 ----
 ***************
 *** 388,394 ****
         aiov.iov_len = uap->nbyte;        auio.uio_iov = &aiov;
         auio.uio_iovcnt = 1;
 !       auio.uio_offset = -1;
         if (uap->nbyte > INT_MAX)
                 return (EINVAL);
         auio.uio_resid = uap->nbyte;
 --- 383,389 ----
         aiov.iov_len = uap->nbyte;
         auio.uio_iov = &aiov;
         auio.uio_iovcnt = 1;
 !       auio.uio_offset = uap->offset;
         if (uap->nbyte > INT_MAX)
                 return (EINVAL);
         auio.uio_resid = uap->nbyte;
 ***************
 *** 403,410 ****
                 ktriov = aiov;
   #endif
         cnt = uap->nbyte;
 -       curoff = fp->f_offset;
 -       fp->f_offset = uap->offset;
         if ((error = (*fp->f_ops->fo_write)(fp, &auio, fp->f_cred))) {
                 if (auio.uio_resid != cnt && (error == ERESTART ||
                     error == EINTR || error == EWOULDBLOCK))
                 if (auio.uio_resid != cnt && (error == ERESTART ||
                     error == EINTR || error == EWOULDBLOCK))
 --- 398,403 ----
 ***************
 *** 413,419 ****                        psignal(p, SIGPIPE);
         }
         cnt -= auio.uio_resid;
 -       fp->f_offset = curoff;
   #ifdef KTRACE
         if (KTRPOINT(p, KTR_GENIO) && error == 0)
                 ktrgenio(p->p_tracep, uap->fd, UIO_WRITE,
 --- 406,411 ----
 
 
 


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