CODEWITHSUNDEEP
linuxprocesslinux-kernelfilesystemssignals
Pratik Shinde
Pratik Shinde

Reputation: 71

Uninterruptable write in Linux

According to an answer on this question : Why doing I/O in Linux is uninterruptible? I/O on linux is uninterruptible (uninterruptible in sleep). But if I start a process ,say a large 'dd' on a file and while the process is going on I forcefully unmount the Filesystem (where the file is),the process gets killed . ideally it should be in a hung state because it is sleeping and is UN.

Upvotes: 0

Views: 439

Answers (1)

Kevin Boone
Kevin Boone

Reputation: 4307

"Uninterruptible" applies to the low-level read/write operations handled by the kernel. In C programming, these correspond broadly to read() and write() calls on the C standard library. That a utility can be interrupted does not say much about whether I/O operations can be interrupted, because a specific file operation in a utility might correspond to many low-level I/O operations.

In the case of dd, the default transfer block size is 512 bytes, so copying a large file might consist of many I/O operations. dd can be interrupted between these operations. I would expect the same to apply to most utilities that operate on files. If you can force them to work with huge data blocks (e.g., specify a gigabyte-size argument for bs= in dd) then you might be able to see that low-level I/O operations are uninterruptible.

Upvotes: 1

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