Michael K. Edwards a écrit :
from sys_write():
file = fget_light(fd, &fput_needed);
if (file) {
loff_t pos = file_pos_read(file);
ret = vfs_write(file, buf, count, &pos);
file_pos_write(file, pos);
fput_light(file, fput_needed);
}
Surely that's racy when two threads write to the same fd and the first
vfs_write call blocks or is preempted. Or does fget_light take some
per-file lock that I'm not seeing?
Nothing in the manuals says that write() on same fd should be non racy : In
particular file pos might be undefined. There is a reason pwrite() exists.
Kernel doesnt have to enforce thread safety as standard is quite clear.
Only O_APPEND case is specially handled (and NFS might fail to handle this
case correctly)
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