File s390-tools-sles12sp3-ziomon-no-blktrace-kill-wh... of Package s390-tools

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File s390-tools-sles12sp3-ziomon-no-blktrace-kill-which-can-corrupt-kernel-blk.patch of Package s390-tools (Revision 4a2eab80a65890b4af79027a6d34954d)

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Subject: [PATCH] [BZ 149058] ziomon: no blktrace kill which can corrupt kernel blktrace state
From: Steffen Maier <maier@linux.vnet.ibm.com>

Description:  ziomon: no blktrace kill which can corrupt kernel blktrace state
Symptom:      Ziomon terminates with the following error messages:

$ ziomon -d <duration> -o <logfile> <device>...
              ...
              ziomon: Failed to stop trace on /dev/sdX
              ...
              ziomon: Failed to stop trace on /dev/sdY
              ziomon: blktrace has leftovers, manual cleanup required!

Subsequent ziomon runs fail likely until the next reboot:

$ ziomon -d <duration> -o <logfile> <device>...
              ...
              Collecting data...BLKTRACESETUP(2) /dev/sdX failed: \
                2/No such file or directory
              BLKTRACESETUP(2) /dev/sdY failed: 2/No such file or directory
              ...
              Thread Z failed open /sys/kernel/debug/block/(null)/traceZ: \
                2/No such file or directory
              FAILED to start thread on CPU 0: 1/Operation not permitted
              ...
              Error: blktrace has errors, aborting
              ...
              ziomon: Failed to stop trace on /dev/sdX
              ...
              ziomon: Failed to stop trace on /dev/sdY
              ziomon: blktrace has leftovers, manual cleanup required!
Problem:      While we call blktrace with stopwatch option '-w $WRP_DURATION'
              to have itself terminate automatically after the (mandatory)
              sampling duration, there might be a race
              with our own timed blktrace checking loop between "Collecting
              data..." and "done"
              or any of SIGHUP SIGTERM SIGINT SIGQUIT from the user might
              prematurely trigger emergency_shutdown(),
              so blktrace might still be running or not have completed its
              cleanup when we reach the blktrace leftover checks in shutdown().

In that case, ziomon uses the meanwhile hidden kill option of
              blktrace which can corrupt kernel state if blktrace user space
              has not yet completed its regular cleanup.
Solution:     The correct way to have the blktrace process terminate and
              cleanup properly including any dependent kernel state, before
              blktrace's stopwatch makes it terminate and cleanup
              automatically, is to only send SIGINT to it.

http://git.kernel.org/cgit/linux/kernel/git/axboe/blktrace.git
              86596c7579c6 ("blktrace: remove -k from manpage synopsis")
              fb7f86674a51 ("blktrace: disable kill option - take 2")
              Additional explanation for blktrace -k:
              http://marc.info/?l=linux-btrace&m=131245973528087&w=2i
              linux-btrace ("Re: Recent changes")
              The following kernel commits do not change above termination
              statement:
              http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git
              39cbb602b543 ("Remove double removal of blktrace directory")
              fd51d251e4cd ("blktrace: remove debugfs entries on bad path")
              f48fc4d32e24
              ("block: get rid of the manual directory counting in blktrace")

As of this writing, the (multithreaded) blktrace also wires
              SIGHUP SIGTERM SIGALRM with the same signal handler
              handle_sigint(), but to adhere to its documentation move from
              SIGTERM to SIGINT anyway.

We must not use the meanwhile hidden kill option of blktrace
              because this corrupts kernel state if blktrace user space has not
              yet completed its regular cleanup.

In order to avoid zombies we wait for all children. After all, we
              want everything to be completed before ziomon terminates and the
              user could safely run another instance of ziomon. Also, we get
              the possibility for users to detect and report issues with
              children that don't finish timely.

Since we do not know how to manually cleanup, drop the check for
              blktrace leftovers in shutdown().
Reproduction: Run ziomon with many devices on the command line.
              Possibly (other) load on the system increases probability.
Upstream-ID:  -
Problem-ID:   149058

Signed-off-by: Steffen Maier <maier@linux.vnet.ibm.com>
---
 ziomon/ziomon |   17 ++++++-----------
 1 file changed, 6 insertions(+), 11 deletions(-)

--- a/ziomon/ziomon
+++ b/ziomon/ziomon
@@ -5,7 +5,7 @@
 #
 # Wrapper script to start all processes
 #
-# Copyright IBM Corp. 2008
+# Copyright IBM Corp. 2008, 2016
 #
 # Author(s): Stefan Raspl <raspl@linux.vnet.ibm.com>
 #
@@ -84,7 +84,7 @@ function check_for_int() {
 
 function print_version() {
    echo "$WRP_TOOLNAME: I/O data collection utility, version %S390_TOOLS_VERSION%";
-   echo "Copyright IBM Corp. 2008";
+   echo "Copyright IBM Corp. 2008, 2016";
 }
 
 
@@ -356,8 +356,6 @@ function start_trace() {
 
 
 function shutdown() {
-   local failed=0;
-
    echo "Shutting down";
    # one more second to write final result
    sleep 2;
@@ -365,7 +363,7 @@ function shutdown() {
       [ -d /proc/$WRP_ZIOMON_UTIL_PID ] && echo "Shutting down utilization process" && kill -s SIGTERM $WRP_ZIOMON_UTIL_PID;
    fi
    if [ "$WRP_BLKTRACE_PID" != "" ]; then
-      [ -d /proc/$WRP_BLKTRACE_PID ] && echo "Shutting down blktrace process" && kill -s SIGTERM $WRP_BLKTRACE_PID;
+      [ -d /proc/$WRP_BLKTRACE_PID ] && echo "Shutting down blktrace process" && kill -s SIGINT $WRP_BLKTRACE_PID;
    fi
    if [ "$WRP_BLKIOMON_PID" != "" ]; then
       [ -d /proc/$WRP_BLKIOMON_PID ] && echo "Shutting down blkiomon process" && kill -s SIGTERM $WRP_BLKIOMON_PID;
@@ -381,12 +379,9 @@ function shutdown() {
          kill -s SIGTERM $WRP_ZIOMON_MGR_PID;
       fi
    fi
-   # kill running traces on devices
-   for dev in ${WRP_DEVICES[@]}; do
-      [ -d /sys/kernel/debug/block/${dev##*/} ] && debug "Trace on $dev exists, attempt to kill..." && blktrace -k $dev >/dev/null 2>&1;
-      [ -d /sys/kernel/debug/block/${dev##*/} ] && echo "$WRP_TOOLNAME: Failed to stop trace on $dev" && (( failed++ ));
-   done
-   [ $failed -ne 0 ] && echo "$WRP_TOOLNAME: blktrace has leftovers, manual cleanup required!";
+   # synchronize with all children to avoid zombies
+   # and to prepare for a clean subsequent re-run of ziomon
+   wait
 
    if [ -e $WRP_MSG_Q_PATH ]; then
       if [ $WRP_DEBUG -gt 1 ]; then

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File s390-tools-sles12sp3-ziomon-no-blktrace-kill-which-can-corrupt-kernel-blk.patch of Package s390-tools (Revision 4a2eab80a65890b4af79027a6d34954d)

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