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Bug 1421802 - The ls program can't be interrupted by a signal
Summary: The ls program can't be interrupted by a signal
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: coreutils
Version: 7.4
Hardware: All
OS: Linux
unspecified
medium
Target Milestone: rc
: ---
Assignee: Kamil Dudka
QA Contact: Alois Mahdal
URL:
Whiteboard:
Depends On: 1365933
Blocks: 1298243 1420851 1465901 1466365
TreeView+ depends on / blocked
 
Reported: 2017-02-13 17:36 UTC by Frank Hirtz
Modified: 2018-04-10 13:15 UTC (History)
12 users (show)

Fixed In Version: coreutils-8.22-19.el7
Doc Type: No Doc Update
Doc Text:
undefined
Clone Of: 1365933
Environment:
Last Closed: 2018-04-10 13:15:16 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHBA-2018:0775 0 None None None 2018-04-10 13:15:45 UTC

Description Frank Hirtz 2017-02-13 17:36:45 UTC 
+++ This bug was initially created as a clone of Bug #1365933 +++

Description of problem:

Whilst debugging some network filesystem stuff, I found that if the open directory system call fails with ERESTARTSYS due to a signal, that signal is deferred by userspace and the system call restarted.  Unfortunately, this means that an ls that is waiting for a network timeout cannot be cancelled with CTRL-C and cannot be suspended with CTRL-Z.

open("/afs/user/dhowells", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = ? ERESTARTSYS (To be restarted if SA_RESTART is set)
--- SIGINT {si_signo=SIGINT, si_code=SI_KERNEL} ---
rt_sigreturn({mask=[]})                 = 2
open("/afs/user/dhowells", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = ? ERESTARTSYS (To be restarted if SA_RESTART is set)
--- SIGQUIT {si_signo=SIGQUIT, si_code=SI_KERNEL} ---
rt_sigreturn({mask=[]})                 = 2
open("/afs/user/dhowells", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFDIR|0777, st_size=2048, ...}) = 0
getdents(3, /* 3 entries */, 32768)     = 80
rt_sigprocmask(SIG_BLOCK, [HUP INT QUIT PIPE ALRM TERM TSTP XCPU XFSZ VTALRM PROF IO], [], 8) = 0
rt_sigaction(SIGINT, {SIG_DFL, [INT], SA_RESTORER|SA_RESTART, 0x7f9c95c93b20}, {0x5640f276ce60, [HUP INT QUIT PIPE ALRM TERM TSTP XCPU XFSZ VTALRM PROF IO], SA_RESTORER|SA_RESTART, 0x7f9c95c93b20}, 8) = 0
tgkill(3954, 3954, SIGINT)              = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
--- SIGINT {si_signo=SIGINT, si_code=SI_TKILL, si_pid=3954, si_uid=0} ---
+++ killed by SIGINT +++

Version-Release number of selected component (if applicable):

coreutils-8.24-6.fc23.x86_64

Unfortunately, it's quite hard to get hold of a directory that will hang for a long enough period of time, but if you can it's quite reproducible.

--- Additional comment from Kamil Dudka on 2016-08-11 04:49:04 EDT ---

Could you please attach gdb while ls is hanging and paste the backtrace?

--- Additional comment from David Howells on 2016-08-11 05:52:25 EDT ---

#0  0x00007faca7731455 in __opendir (name=0x560b8766cc90 "/afs/user/dhowells")
    at ../sysdeps/posix/opendir.c:200
#1  0x0000560b8744caed in print_dir (command_line_arg=<optimized out>, 
    realname=0x0, name=<optimized out>) at src/ls.c:2551
#2  main (argc=<optimized out>, argv=<optimized out>) at src/ls.c:1457

--- Additional comment from Kamil Dudka on 2016-08-11 07:23:12 EDT ---

Does it work as expected with --color=none or if stdout is redirected off terminal?

--- Additional comment from David Howells on 2016-08-11 07:51:47 EDT ---

ls --color=none can be interrupted, as can ls >/tmp/foo.  A subsequent ls without anything special will then still be uninterruptible until the network timeout occurs.

--- Additional comment from Kamil Dudka on 2016-08-11 08:22:48 EDT ---

If ls prints to a terminal, it postpones processing of signals to always leave terminal in a consistent state when being terminated or suspended.  A possible solution would be to disable SA_RESTART before calling opendir() and process signals synchronously in an EINTR loop.  Nevertheless, I am afraid we will hit the same issue with subsequent stat() calls if the -l option is used.

--- Additional comment from Kamil Dudka on 2016-08-15 10:05:35 EDT ---

reported upstream:
http://lists.gnu.org/archive/html/bug-coreutils/2016-08/msg00010.html

--- Additional comment from Kamil Dudka on 2016-09-06 08:53 EDT ---

... until they are actually needed.  That is right before the first
escape sequence is printed to a terminal.

--- Additional comment from Kamil Dudka on 2016-09-06 08:54:39 EDT ---

Could you please test the attached patch?  Does it solve the problem for you?

I can prepare a scratch build for Fedora release of your choice if needed...

--- Additional comment from David Howells on 2016-09-06 11:09:42 EDT ---

The patch works for me.  If I make afs_open() in the kernel sleep till a signal happens than then return -ERESTARTSYS, the old ls just restarts the open() system call when I press CTRL-C, but the patched ls is correctly killed by SIGINT.

--- Additional comment from Kamil Dudka on 2016-09-06 11:42:04 EDT ---

Thank you for testing the patch!  I have proposed it to cureutils upstream:

http://debbugs.gnu.org/cgi/bugreport.cgi?bug=24232#17

--- Additional comment from Pádraig Brady on 2016-09-07 05:19:45 EDT ---

Upstream patch: http://git.sv.gnu.org/gitweb/?p=coreutils.git;a=commitdiff;h=v8.25-63-g5445f78

--- Additional comment from Kamil Dudka on 2016-09-07 14:30:01 EDT ---

Thanks for the upstream commit!  Included in coreutils-8.25-15.fc26...

--- Additional comment from Fedora Update System on 2016-10-31 13:44:26 EDT ---

coreutils-8.25-15.fc25 has been submitted as an update to Fedora 25. https://bodhi.fedoraproject.org/updates/FEDORA-2016-be13b257bb

--- Additional comment from Fedora Update System on 2016-10-31 13:46:17 EDT ---

coreutils-8.25-7.fc24 has been submitted as an update to Fedora 24. https://bodhi.fedoraproject.org/updates/FEDORA-2016-75adc7da4f

--- Additional comment from Fedora Update System on 2016-10-31 22:22:13 EDT ---

coreutils-8.25-15.fc25 has been pushed to the Fedora 25 testing repository. If problems still persist, please make note of it in this bug report.
See https://fedoraproject.org/wiki/QA:Updates_Testing for
instructions on how to install test updates.
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2016-be13b257bb

--- Additional comment from Fedora Update System on 2016-11-01 14:22:54 EDT ---

coreutils-8.25-7.fc24 has been pushed to the Fedora 24 testing repository. If problems still persist, please make note of it in this bug report.
See https://fedoraproject.org/wiki/QA:Updates_Testing for
instructions on how to install test updates.
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2016-75adc7da4f

--- Additional comment from Fedora Update System on 2016-11-03 14:29:36 EDT ---

coreutils-8.25-15.fc25 has been pushed to the Fedora 25 stable repository. If problems still persist, please make note of it in this bug report.

--- Additional comment from Fedora Update System on 2016-11-03 19:55:08 EDT ---

coreutils-8.25-7.fc24 has been pushed to the Fedora 24 stable repository. If problems still persist, please make note of it in this bug report.

--- Additional comment from Fedora Update System on 2016-11-19 16:06:42 EST ---

coreutils-8.25-15.fc25 has been pushed to the Fedora 25 stable repository. If problems still persist, please make note of it in this bug report.
Comment 2 Kamil Dudka 2017-02-13 18:08:31 UTC 
Does it work as expected with --color=none or if stdout is redirected off terminal?
Comment 3 Frank Hirtz 2017-02-13 18:11:29 UTC 
Reportedly, yes. The client tested this based on the discussion in the original ticket and has proposed it internally as a workaround.
Comment 4 Kamil Dudka 2017-02-13 18:23:21 UTC 
I am fine with applying the patch on RHEL-7, too, if this bug gets approved.  There have been no problems with the patch in Fedora as far as I know...
Comment 10 Alois Mahdal 2018-02-23 23:11:56 UTC 
No reliable reproducer available, and according to anove comments, patch has been tested in both Fedora and internally by OP.  Falling back to SanityOnly.

Test suite ran, no SUT problems found.
Comment 13 errata-xmlrpc 2018-04-10 13:15:16 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2018:0775
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