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Top Forums Programming write() issue during a low level hdd access Post 302397634 by Corona688 on Monday 22nd of February 2010 08:04:52 PM
Old 02-22-2010
Quote:
Originally Posted by sponnusa
If I call libata calls directly in my program
you don't "call" libata. It's a device driver.
Quote:
Though Linux is programmer friendly, I feel not much control is given to the programmer
Au contraire. You can dump ISO images direct from CDROM drives. You can write to memory raw, and talk to raw I/O ports. In windows, this takes a device driver. In Linux, all it needs is device permissions. It's just more generally recognized in UNIX circles that this is a horrible idea in general, while old-fashioned Windows programmers are still reeling from the shock and betrayal of having to give up real mode at gunpoint ;p
Quote:
I don't know if I am going into a vicious circle of kernel hacking / Linux abuse mode, but I just don't feel some things are right with Linux! Smilie
Tell me, what does raw I/O even mean with a hard drive? Are you going to play with the DMA controller, set up interrupts, and send asynchronous requests yourself? Your idea of "raw I/O" hasn't much to do with what the drive is actually doing. Try the linux kernel mailing list if you're interested in truly raw I/O.
Quote:
I have tried posix_fadvise, but the read / write calls are locking up on the bad sectors as said by you.
Congratulations, it's working. It's not the program that's locking up. The drive itself is trying to read the sector, failing, and taking many minutes of retrying before it gives up and informs the computer it can't.
Quote:
Is there any timeout option that can be set on the Read / Write operations to say to the program / kernel to move on to the next sector / block based on the timeout (time consumed for the current sector)?
The timeout is in the drive hardware itself. If it's configurable at all it might be one of the many things hdparm can do. Which incidentally might be something interesting to look at the source of for talking to drives on a low level.

Last edited by Corona688; 02-22-2010 at 09:27 PM..
 

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Tcl_Access(3)						      Tcl Library Procedures						     Tcl_Access(3)

__________________________________________________________________________________________________________________________________________________

NAME
Tcl_Access, Tcl_Stat - check file permissions and other attributes SYNOPSIS
#include <tcl.h> int Tcl_Access(path, mode) int Tcl_Stat(path, statPtr) ARGUMENTS
char *path (in) Native name of the file to check the attributes of. int mode (in) Mask consisting of one or more of R_OK, W_OK, X_OK and F_OK. R_OK, W_OK and X_OK request checking whether the file exists and has read, write and execute permissions, respectively. F_OK just requests checking for the existence of the file. struct stat *statPtr (out) The structure that contains the result. _________________________________________________________________ DESCRIPTION
As of Tcl 8.4, the object-based APIs Tcl_FSAccess and Tcl_FSStat should be used in preference to Tcl_Access and Tcl_Stat, wherever possi- ble. There are two reasons for calling Tcl_Access and Tcl_Stat rather than calling system level functions access and stat directly. First, the Windows implementation of both functions fixes some bugs in the system level calls. Second, both Tcl_Access and Tcl_Stat (as well as Tcl_OpenFileChannelProc) hook into a linked list of functions. This allows the possibility to reroute file access to alternative media or access methods. Tcl_Access checks whether the process would be allowed to read, write or test for existence of the file (or other file system object) whose name is pathname. If pathname is a symbolic link on Unix, then permissions of the file referred by this symbolic link are tested. On success (all requested permissions granted), zero is returned. On error (at least one bit in mode asked for a permission that is denied, or some other error occurred), -1 is returned. Tcl_Stat fills the stat structure statPtr with information about the specified file. You do not need any access rights to the file to get this information but you need search rights to all directories named in the path leading to the file. The stat structure includes info regarding device, inode (always 0 on Windows), privilege mode, nlink (always 1 on Windows), user id (always 0 on Windows), group id (always 0 on Windows), rdev (same as device on Windows), size, last access time, last modification time, and creation time. If path exists, Tcl_Stat returns 0 and the stat structure is filled with data. Otherwise, -1 is returned, and no stat info is given. KEYWORDS
stat, access Tcl 8.1 Tcl_Access(3)
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