From bcbd925da0544249bd31ffab04bd65bdbdc3d10f Mon Sep 17 00:00:00 2001 From: Filipe David Borba Manana Date: Sun, 9 Dec 2012 03:33:47 +0000 Subject: 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 --- erts/emulator/drivers/common/efile_drv.c | 23 ++++++++++++++++++----- 1 file changed, 18 insertions(+), 5 deletions(-) (limited to 'erts/emulator/drivers') diff --git a/erts/emulator/drivers/common/efile_drv.c b/erts/emulator/drivers/common/efile_drv.c index 912f5d3d8b..2ac7f169af 100644 --- a/erts/emulator/drivers/common/efile_drv.c +++ b/erts/emulator/drivers/common/efile_drv.c @@ -439,6 +439,7 @@ struct t_data Efile_error errInfo; int flags; SWord fd; + int is_fd_unused; /**/ Efile_info info; EFILE_DIR_HANDLE dir_handle; /* Handle to open directory. */ @@ -781,11 +782,6 @@ file_start(ErlDrvPort port, char* command) return (ErlDrvData) desc; } -static void free_data(void *data) -{ - EF_FREE(data); -} - static void do_close(int flags, SWord fd) { if (flags & EFILE_COMPRESSED) { erts_gzclose((gzFile)(fd)); @@ -803,6 +799,17 @@ static void invoke_close(void *data) DTRACE_INVOKE_RETURN(FILE_CLOSE); } +static void free_data(void *data) +{ + struct t_data *d = (struct t_data *) data; + + if (d->command == FILE_OPEN && d->is_fd_unused && d->fd != FILE_FD_INVALID) { + do_close(d->flags, d->fd); + } + + EF_FREE(data); +} + /********************************************************************* * Driver entry point -> stop */ @@ -1862,6 +1869,9 @@ static void invoke_open(void *data) } d->result_ok = status; + if (!status) { + d->fd = FILE_FD_INVALID; + } DTRACE_INVOKE_RETURN(FILE_OPEN); } @@ -2373,8 +2383,10 @@ file_async_ready(ErlDrvData e, ErlDrvThreadData data) if (!d->result_ok) { reply_error(desc, &d->errInfo); } else { + ASSERT(d->is_fd_unused); desc->fd = d->fd; desc->flags = d->flags; + d->is_fd_unused = 0; reply_Uint(desc, d->fd); } free_data(data); @@ -2745,6 +2757,7 @@ file_output(ErlDrvData e, char* buf, ErlDrvSizeT count) d->invoke = invoke_open; d->free = free_data; d->level = 2; + d->is_fd_unused = 1; goto done; } -- cgit v1.2.3