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
objdiff
#!/bin/bash
# objdiff - a small script for validating that a commit or series of commits
# didn't change object code.
#
# Copyright 2014, Jason Cooper <jason@lakedaemon.net>
#
# Licensed under the terms of the GNU GPL version 2
# usage example:
#
# $ git checkout COMMIT_A
# $ <your fancy build command here>
# $ ./scripts/objdiff record path/to/*.o
#
# $ git checkout COMMIT_B
# $ <your fancy build command here>
# $ ./scripts/objdiff record path/to/*.o
#
# $ ./scripts/objdiff diff COMMIT_A COMMIT_B
# $
# And to clean up (everything is in .tmp_objdiff/*)
# $ ./scripts/objdiff clean all
#
# Note: 'make mrproper' will also remove .tmp_objdiff
GIT_DIR="`git rev-parse --git-dir`"
if [ -d "$GIT_DIR" ]; then
TMPD="${GIT_DIR%git}tmp_objdiff"
[ -d "$TMPD" ] || mkdir "$TMPD"
else
echo "ERROR: git directory not found."
exit 1
fi
usage() {
echo "Usage: $0 <command> <args>"
echo " record <list of object files>"
echo " diff <commitA> <commitB>"
echo " clean all | <commit>"
exit 1
}
dorecord() {
[ $# -eq 0 ] && usage
FILES="$*"
CMT="`git rev-parse --short HEAD`"
OBJDUMP="${CROSS_COMPILE}objdump"
OBJDIFFD="$TMPD/$CMT"
[ ! -d "$OBJDIFFD" ] && mkdir -p "$OBJDIFFD"
for f in $FILES; do
dn="${f%/*}"
bn="${f##*/}"
[ ! -d "$OBJDIFFD/$dn" ] && mkdir -p "$OBJDIFFD/$dn"
# remove addresses for a more clear diff
# http://dummdida.tumblr.com/post/60924060451/binary-diff-between-libc-from-scientificlinux-and
$OBJDUMP -D "$f" | sed "s/^[[:space:]]\+[0-9a-f]\+//" \
>"$OBJDIFFD/$dn/$bn"
done
}
dodiff() {
[ $# -ne 2 ] && [ $# -ne 0 ] && usage
if [ $# -eq 0 ]; then
SRC="`git rev-parse --short HEAD^`"
DST="`git rev-parse --short HEAD`"
else
SRC="`git rev-parse --short $1`"
DST="`git rev-parse --short $2`"
fi
DIFF="`which colordiff`"
if [ ${#DIFF} -eq 0 ] || [ ! -x "$DIFF" ]; then
DIFF="`which diff`"
fi
SRCD="$TMPD/$SRC"
DSTD="$TMPD/$DST"
if [ ! -d "$SRCD" ]; then
echo "ERROR: $SRCD doesn't exist"
exit 1
fi
if [ ! -d "$DSTD" ]; then
echo "ERROR: $DSTD doesn't exist"
exit 1
fi
$DIFF -Nurd $SRCD $DSTD
}
doclean() {
[ $# -eq 0 ] && usage
[ $# -gt 1 ] && usage
if [ "x$1" = "xall" ]; then
rm -rf $TMPD/*
else
CMT="`git rev-parse --short $1`"
if [ -d "$TMPD/$CMT" ]; then
rm -rf $TMPD/$CMT
else
echo "$CMT not found"
fi
fi
}
[ $# -eq 0 ] && usage
case "$1" in
record)
shift
dorecord $*
;;
diff)
shift
dodiff $*
;;
clean)
shift
doclean $*
;;
*)
echo "Unrecognized command '$1'"
exit 1
;;
esac
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