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library: find tty device name of process quicker

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The procps library attempts to work out the tty of a process
through several methods. For things like /dev/tty123 or
/dev/foo it works fine.

For tty devices that put the minor number in a directory
of the major name this fails. So then we have to fallback
to stating things like the processes STDERR and try again.

Considering a lot of processes sit on ttys such as
/dev/pts/3 this is a lot of wasted time. At the point of
entering driver_name we know "/dev/pts" and we know "3"
we just didn't join them up the right way as this is old
code.

This change now looks for /dev/pts/3 as well. It does it
after looking for /dev/pts3 so the behaviour is the same.

References:
 https://bugs.debian.org/770215

Signed-off-by: Craig Small <csmall@enc.com.au>
This commit is contained in:
Simon Tatham 2016-07-03 10:08:18 +10:00 committed by Craig Small
parent 5a40c7970d
commit 365cb37029
2 changed files with 8 additions and 4 deletions
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3
NEWS
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@ -5,8 +5,9 @@ procps-ng-NEXT
* ps: Fallback to attr/current for context Debian #786956
* tests: Conditionally add prctl Debian #816237
* pidof: check cmd if space in argv0. GitLab #4
* kill: report error if cannot kill process #733172
* kill: report error if cannot kill process Debian #733172
* watch: Add hostname to header
* library: Find tty quicker Debian #770215
procps-ng-3.3.11
----------------

3
proc/devname.c
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@ -132,11 +132,14 @@ static int driver_name(char *restrict const buf, unsigned maj, unsigned min){
tmn = tmn->next;
}
sprintf(buf, "/dev/%s%d", tmn->name, min); /* like "/dev/ttyZZ255" */
if(stat(buf, &sbuf) < 0){
sprintf(buf, "/dev/%s/%d", tmn->name, min); /* like "/dev/pts/255" */
if(stat(buf, &sbuf) < 0){
if(tmn->devfs_type) return 0;
sprintf(buf, "/dev/%s", tmn->name); /* like "/dev/ttyZZ255" */
if(stat(buf, &sbuf) < 0) return 0;
}
}
if(min != MINOR_OF(sbuf.st_rdev)) return 0;
if(maj != MAJOR_OF(sbuf.st_rdev)) return 0;
return 1;