Messages in this thread | | | Date | Wed, 21 Dec 2011 10:10:47 -0800 | From | Earl Chew <> | Subject | RFC: Inconsistent short read behaviour in __do_proc_dointvec vs _proc_do_string |
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Should repeated short reads in __do_proc_dointvec behave consistently with _proc_do_string ?
Consider:
> char c[1]; > int n; > > while (1) > { > n = read(0, c, 1); > > if (n <= 0) break; > > write (1, c, 1); > }
Running this program on /proc/self/stat emits the expected output.
Running this program on /proc/sys/kernel/random/poolsize does not :-(
The issue is that __do_proc_dointvec does not accommodate non-zero file positions when reading:
> if (!tbl_data || !table->maxlen || !*lenp || (*ppos && !write)) { > *lenp = 0; > return 0; > }
OTOH _proc_do_string seems quite willing to accommodate it:
> if (write) { > ... > } else { > len = strlen(data); > if (len > maxlen) > len = maxlen; > > if (*ppos > len) { > *lenp = 0; > return 0; > }
Should __do_proc_intvec behave more like _proc_do_string, or vice-versa ?
Earl
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