diff options
author | Filipe David Borba Manana <[email protected]> | 2012-12-09 03:33:47 +0000 |
---|---|---|
committer | Björn-Egil Dahlberg <[email protected]> | 2013-01-09 16:58:49 +0100 |
commit | bcbd925da0544249bd31ffab04bd65bdbdc3d10f (patch) | |
tree | c77e8a7ffe75e382c32880479554c31d8ec5ccd8 /erts/prebuild.skip | |
parent | 5cd05af9b0ed994cf44bbd8ad7c5ee3119f952ff (diff) | |
download | otp-bcbd925da0544249bd31ffab04bd65bdbdc3d10f.tar.gz otp-bcbd925da0544249bd31ffab04bd65bdbdc3d10f.tar.bz2 otp-bcbd925da0544249bd31ffab04bd65bdbdc3d10f.zip |
Fix fd leak when using async thread pool
When using the async thread pool, if an erlang process
asks to open a file and it gets shutdown/killed while
the file:open/2 call hasn't returned, it's possible to
leak a file descriptor against the target file.
This happens because when the file driver is stopped
(file_stop() function is called), an async thread is
executing, about to execute, or executed already the
invoke_open() function. After file_stop() is called,
the file_async_ready() function will not run, and this
function is responsible for setting desc->fd with the
file descriptor that invoke_open() got. The file_stop()
call closes desc->fd if it refers to a valid file
descriptor, which is not the case here, because this
function was called before file_async_ready() could
run.
This leak is easily reproducile in a GNU/Linux system
using the following test code:
-module(t).
-export([t/1]).
t(N) ->
Pid = spawn_link(fun() ->
process_flag(trap_exit, true),
loop(N)
end),
Ref = erlang:monitor(process, Pid),
receive {'DOWN', Ref, _, _, _} ->
ok
end.
loop(0) ->
ok;
loop(N) ->
Name = integer_to_list(N),
Server = self(),
Pid = spawn(fun() ->
Server ! continue,
{ok, FdW} = file:open(Name, [raw, write]),
{ok, FdR} = file:open(Name, [raw, read]),
% Optional close calls, with or without them
% it makes no difference.
%ok = file:close(FdW),
%ok = file:close(FdR),
ok
end),
receive continue -> ok end,
exit(Pid, shutdown),
loop(N - 1).
Running this code with a few iterations is enough to very often
notice, with the lsof command, that the beam.smp process is holding
forever file descriptors open. This issue doesn't happen if the
async thread pool is not used.
Example:
$ erl +A 4
Erlang R15B03 (erts-5.9.3) [source] [64-bit] [smp:4:4] [async-threads:4] [hipe] [kernel-poll:false]
Eshell V5.9.3 (abort with ^G)
1> c(t).
{ok,t}
2> os:getpid().
"31975"
3> t:t(20).
ok
In a separate shell:
$ lsof -p 31975
COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME
beam.smp 31975 fdmanana cwd DIR 8,18 22736896 32563204 /home/fdmanana/git/hub/otp/tmp
beam.smp 31975 fdmanana rtd DIR 8,1 4096 2 /
beam.smp 31975 fdmanana txt REG 8,1 7600263 1835126 /opt/r15b03/lib/erlang/erts-5.9.3/bin/beam.smp
beam.smp 31975 fdmanana mem REG 8,1 7220736 2497283 /usr/lib/locale/locale-archive
beam.smp 31975 fdmanana mem REG 8,1 10280 2505021 /usr/lib/libsctp.so.1.0.11
beam.smp 31975 fdmanana mem REG 8,1 1811128 917795 /lib/x86_64-linux-gnu/libc-2.15.so
beam.smp 31975 fdmanana mem REG 8,1 31752 917803 /lib/x86_64-linux-gnu/librt-2.15.so
beam.smp 31975 fdmanana mem REG 8,1 135366 917799 /lib/x86_64-linux-gnu/libpthread-2.15.so
beam.smp 31975 fdmanana mem REG 8,1 159200 921249 /lib/x86_64-linux-gnu/libtinfo.so.5.9
beam.smp 31975 fdmanana mem REG 8,1 1030512 917962 /lib/x86_64-linux-gnu/libm-2.15.so
beam.smp 31975 fdmanana mem REG 8,1 14768 917702 /lib/x86_64-linux-gnu/libdl-2.15.so
beam.smp 31975 fdmanana mem REG 8,1 149280 917974 /lib/x86_64-linux-gnu/ld-2.15.so
beam.smp 31975 fdmanana 0u CHR 136,1 4 /dev/pts/1
beam.smp 31975 fdmanana 1u CHR 136,1 4 /dev/pts/1
beam.smp 31975 fdmanana 2u CHR 136,1 4 /dev/pts/1
beam.smp 31975 fdmanana 3r FIFO 0,8 1298297 pipe
beam.smp 31975 fdmanana 4w FIFO 0,8 1298297 pipe
beam.smp 31975 fdmanana 5r FIFO 0,8 1298298 pipe
beam.smp 31975 fdmanana 6w FIFO 0,8 1298298 pipe
beam.smp 31975 fdmanana 7w REG 8,18 0 32564173 /home/fdmanana/git/hub/otp/tmp/20
beam.smp 31975 fdmanana 8w REG 8,18 0 32564176 /home/fdmanana/git/hub/otp/tmp/16
beam.smp 31975 fdmanana 9w REG 8,18 0 32564177 /home/fdmanana/git/hub/otp/tmp/15
beam.smp 31975 fdmanana 10w REG 8,18 0 32564179 /home/fdmanana/git/hub/otp/tmp/12
beam.smp 31975 fdmanana 11w REG 8,18 0 32564180 /home/fdmanana/git/hub/otp/tmp/11
beam.smp 31975 fdmanana 12w REG 8,18 0 32564205 /home/fdmanana/git/hub/otp/tmp/10
beam.smp 31975 fdmanana 13w REG 8,18 0 32564182 /home/fdmanana/git/hub/otp/tmp/8
beam.smp 31975 fdmanana 14w REG 8,18 0 32564183 /home/fdmanana/git/hub/otp/tmp/7
beam.smp 31975 fdmanana 15w REG 8,18 0 32564186 /home/fdmanana/git/hub/otp/tmp/3
Diffstat (limited to 'erts/prebuild.skip')
0 files changed, 0 insertions, 0 deletions