https://github.com/torvalds/linux
Revision 0c36b390a546055b6815d4b93a2c9fed4d980ffb authored by Sebastian Ott on 04 June 2014, 13:58:24 UTC, committed by Tejun Heo on 04 June 2014, 16:12:29 UTC
The percpu-refcount infrastructure uses the underscore variants of this_cpu_ops in order to modify percpu reference counters. (e.g. __this_cpu_inc()). However the underscore variants do not atomically update the percpu variable, instead they may be implemented using read-modify-write semantics (more than one instruction). Therefore it is only safe to use the underscore variant if the context is always the same (process, softirq, or hardirq). Otherwise it is possible to lose updates. This problem is something that Sebastian has seen within the aio subsystem which uses percpu refcounters both in process and softirq context leading to reference counts that never dropped to zeroes; even though the number of "get" and "put" calls matched. Fix this by using the non-underscore this_cpu_ops variant which provides correct per cpu atomic semantics and fixes the corrupted reference counts. Cc: Kent Overstreet <kmo@daterainc.com> Cc: <stable@vger.kernel.org> # v3.11+ Reported-by: Sebastian Ott <sebott@linux.vnet.ibm.com> Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Tejun Heo <tj@kernel.org> References: http://lkml.kernel.org/g/alpine.LFD.2.11.1406041540520.21183@denkbrett
1 parent 5a838c3
Tip revision: 0c36b390a546055b6815d4b93a2c9fed4d980ffb authored by Sebastian Ott on 04 June 2014, 13:58:24 UTC
percpu-refcount: fix usage of this_cpu_ops
percpu-refcount: fix usage of this_cpu_ops
Tip revision: 0c36b39
coccicheck
#!/bin/bash
#
# This script requires at least spatch
# version 1.0.0-rc11.
#
SPATCH="`which ${SPATCH:=spatch}`"
trap kill_running SIGTERM SIGINT
declare -a SPATCH_PID
# The verbosity may be set by the environmental parameter V=
# as for example with 'make V=1 coccicheck'
if [ -n "$V" -a "$V" != "0" ]; then
VERBOSE="$V"
else
VERBOSE=0
fi
if [ -z "$J" ]; then
NPROC=$(getconf _NPROCESSORS_ONLN)
else
NPROC="$J"
fi
FLAGS="$SPFLAGS --very-quiet"
# spatch only allows include directories with the syntax "-I include"
# while gcc also allows "-Iinclude" and "-include include"
COCCIINCLUDE=${LINUXINCLUDE//-I/-I }
COCCIINCLUDE=${COCCIINCLUDE//-include/-I}
if [ "$C" = "1" -o "$C" = "2" ]; then
ONLINE=1
# Take only the last argument, which is the C file to test
shift $(( $# - 1 ))
OPTIONS="$COCCIINCLUDE $1"
else
ONLINE=0
if [ "$KBUILD_EXTMOD" = "" ] ; then
OPTIONS="--dir $srctree $COCCIINCLUDE"
else
OPTIONS="--dir $KBUILD_EXTMOD $COCCIINCLUDE"
fi
fi
if [ "$KBUILD_EXTMOD" != "" ] ; then
OPTIONS="--patch $srctree $OPTIONS"
fi
if [ ! -x "$SPATCH" ]; then
echo 'spatch is part of the Coccinelle project and is available at http://coccinelle.lip6.fr/'
exit 1
fi
if [ "$MODE" = "" ] ; then
if [ "$ONLINE" = "0" ] ; then
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echo 'Available modes are the following: patch, report, context, org'
echo 'You can specify the mode with "make coccicheck MODE=<mode>"'
echo 'Note however that some modes are not implemented by some semantic patches.'
fi
MODE="report"
fi
if [ "$MODE" = "chain" ] ; then
if [ "$ONLINE" = "0" ] ; then
echo 'You have selected the "chain" mode.'
echo 'All available modes will be tried (in that order): patch, report, context, org'
fi
elif [ "$MODE" = "report" -o "$MODE" = "org" ] ; then
FLAGS="$FLAGS --no-show-diff"
fi
if [ "$ONLINE" = "0" ] ; then
echo ''
echo 'Please check for false positives in the output before submitting a patch.'
echo 'When using "patch" mode, carefully review the patch before submitting it.'
echo ''
fi
run_cmd() {
local i
if [ $VERBOSE -ne 0 ] ; then
echo "Running ($NPROC in parallel): $@"
fi
for i in $(seq 0 $(( NPROC - 1)) ); do
eval "$@ --max $NPROC --index $i &"
SPATCH_PID[$i]=$!
if [ $VERBOSE -eq 2 ] ; then
echo "${SPATCH_PID[$i]} running"
fi
done
wait
}
kill_running() {
for i in $(seq $(( NPROC - 1 )) ); do
if [ $VERBOSE -eq 2 ] ; then
echo "Killing ${SPATCH_PID[$i]}"
fi
kill ${SPATCH_PID[$i]} 2>/dev/null
done
}
coccinelle () {
COCCI="$1"
OPT=`grep "Option" $COCCI | cut -d':' -f2`
# The option '--parse-cocci' can be used to syntactically check the SmPL files.
#
# $SPATCH -D $MODE $FLAGS -parse_cocci $COCCI $OPT > /dev/null
if [ $VERBOSE -ne 0 -a $ONLINE -eq 0 ] ; then
FILE=`echo $COCCI | sed "s|$srctree/||"`
echo "Processing `basename $COCCI`"
echo "with option(s) \"$OPT\""
echo ''
echo 'Message example to submit a patch:'
sed -ne 's|^///||p' $COCCI
if [ "$MODE" = "patch" ] ; then
echo ' The semantic patch that makes this change is available'
elif [ "$MODE" = "report" ] ; then
echo ' The semantic patch that makes this report is available'
elif [ "$MODE" = "context" ] ; then
echo ' The semantic patch that spots this code is available'
elif [ "$MODE" = "org" ] ; then
echo ' The semantic patch that makes this Org report is available'
else
echo ' The semantic patch that makes this output is available'
fi
echo " in $FILE."
echo ''
echo ' More information about semantic patching is available at'
echo ' http://coccinelle.lip6.fr/'
echo ''
if [ "`sed -ne 's|^//#||p' $COCCI`" ] ; then
echo 'Semantic patch information:'
sed -ne 's|^//#||p' $COCCI
echo ''
fi
fi
if [ "$MODE" = "chain" ] ; then
run_cmd $SPATCH -D patch \
$FLAGS --cocci-file $COCCI $OPT $OPTIONS || \
run_cmd $SPATCH -D report \
$FLAGS --cocci-file $COCCI $OPT $OPTIONS --no-show-diff || \
run_cmd $SPATCH -D context \
$FLAGS --cocci-file $COCCI $OPT $OPTIONS || \
run_cmd $SPATCH -D org \
$FLAGS --cocci-file $COCCI $OPT $OPTIONS --no-show-diff || exit 1
elif [ "$MODE" = "rep+ctxt" ] ; then
run_cmd $SPATCH -D report \
$FLAGS --cocci-file $COCCI $OPT $OPTIONS --no-show-diff && \
run_cmd $SPATCH -D context \
$FLAGS --cocci-file $COCCI $OPT $OPTIONS || exit 1
else
run_cmd $SPATCH -D $MODE $FLAGS --cocci-file $COCCI $OPT $OPTIONS || exit 1
fi
}
if [ "$COCCI" = "" ] ; then
for f in `find $srctree/scripts/coccinelle/ -name '*.cocci' -type f | sort`; do
coccinelle $f
done
else
coccinelle $COCCI
fi
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