Revision e2093926a098a8ccf0f1d10f6df8dad452cb28d3 authored by Ross Zwisler on 02 June 2017, 21:46:37 UTC, committed by Linus Torvalds on 02 June 2017, 22:07:37 UTC
We currently have two related PMD vs PTE races in the DAX code. These can both be easily triggered by having two threads reading and writing simultaneously to the same private mapping, with the key being that private mapping reads can be handled with PMDs but private mapping writes are always handled with PTEs so that we can COW. Here is the first race: CPU 0 CPU 1 (private mapping write) __handle_mm_fault() create_huge_pmd() - FALLBACK handle_pte_fault() passes check for pmd_devmap() (private mapping read) __handle_mm_fault() create_huge_pmd() dax_iomap_pmd_fault() inserts PMD dax_iomap_pte_fault() does a PTE fault, but we already have a DAX PMD installed in our page tables at this spot. Here's the second race: CPU 0 CPU 1 (private mapping read) __handle_mm_fault() passes check for pmd_none() create_huge_pmd() dax_iomap_pmd_fault() inserts PMD (private mapping write) __handle_mm_fault() create_huge_pmd() - FALLBACK (private mapping read) __handle_mm_fault() passes check for pmd_none() create_huge_pmd() handle_pte_fault() dax_iomap_pte_fault() inserts PTE dax_iomap_pmd_fault() inserts PMD, but we already have a PTE at this spot. The core of the issue is that while there is isolation between faults to the same range in the DAX fault handlers via our DAX entry locking, there is no isolation between faults in the code in mm/memory.c. This means for instance that this code in __handle_mm_fault() can run: if (pmd_none(*vmf.pmd) && transparent_hugepage_enabled(vma)) { ret = create_huge_pmd(&vmf); But by the time we actually get to run the fault handler called by create_huge_pmd(), the PMD is no longer pmd_none() because a racing PTE fault has installed a normal PMD here as a parent. This is the cause of the 2nd race. The first race is similar - there is the following check in handle_pte_fault(): } else { /* See comment in pte_alloc_one_map() */ if (pmd_devmap(*vmf->pmd) || pmd_trans_unstable(vmf->pmd)) return 0; So if a pmd_devmap() PMD (a DAX PMD) has been installed at vmf->pmd, we will bail and retry the fault. This is correct, but there is nothing preventing the PMD from being installed after this check but before we actually get to the DAX PTE fault handlers. In my testing these races result in the following types of errors: BUG: Bad rss-counter state mm:ffff8800a817d280 idx:1 val:1 BUG: non-zero nr_ptes on freeing mm: 15 Fix this issue by having the DAX fault handlers verify that it is safe to continue their fault after they have taken an entry lock to block other racing faults. [ross.zwisler@linux.intel.com: improve fix for colliding PMD & PTE entries] Link: http://lkml.kernel.org/r/20170526195932.32178-1-ross.zwisler@linux.intel.com Link: http://lkml.kernel.org/r/20170522215749.23516-2-ross.zwisler@linux.intel.com Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com> Reported-by: Pawel Lebioda <pawel.lebioda@intel.com> Reviewed-by: Jan Kara <jack@suse.cz> Cc: "Darrick J. Wong" <darrick.wong@oracle.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Christoph Hellwig <hch@lst.de> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Matthew Wilcox <mawilcox@microsoft.com> Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com> Cc: Pawel Lebioda <pawel.lebioda@intel.com> Cc: Dave Jiang <dave.jiang@intel.com> Cc: Xiong Zhou <xzhou@redhat.com> Cc: Eryu Guan <eguan@redhat.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent d0f0931
checkkconfigsymbols.py
#!/usr/bin/env python3
"""Find Kconfig symbols that are referenced but not defined."""
# (c) 2014-2017 Valentin Rothberg <valentinrothberg@gmail.com>
# (c) 2014 Stefan Hengelein <stefan.hengelein@fau.de>
#
# Licensed under the terms of the GNU GPL License version 2
import argparse
import difflib
import os
import re
import signal
import subprocess
import sys
from multiprocessing import Pool, cpu_count
# regex expressions
OPERATORS = r"&|\(|\)|\||\!"
SYMBOL = r"(?:\w*[A-Z0-9]\w*){2,}"
DEF = r"^\s*(?:menu){,1}config\s+(" + SYMBOL + r")\s*"
EXPR = r"(?:" + OPERATORS + r"|\s|" + SYMBOL + r")+"
DEFAULT = r"default\s+.*?(?:if\s.+){,1}"
STMT = r"^\s*(?:if|select|imply|depends\s+on|(?:" + DEFAULT + r"))\s+" + EXPR
SOURCE_SYMBOL = r"(?:\W|\b)+[D]{,1}CONFIG_(" + SYMBOL + r")"
# regex objects
REGEX_FILE_KCONFIG = re.compile(r".*Kconfig[\.\w+\-]*$")
REGEX_SYMBOL = re.compile(r'(?!\B)' + SYMBOL + r'(?!\B)')
REGEX_SOURCE_SYMBOL = re.compile(SOURCE_SYMBOL)
REGEX_KCONFIG_DEF = re.compile(DEF)
REGEX_KCONFIG_EXPR = re.compile(EXPR)
REGEX_KCONFIG_STMT = re.compile(STMT)
REGEX_KCONFIG_HELP = re.compile(r"^\s+(help|---help---)\s*$")
REGEX_FILTER_SYMBOLS = re.compile(r"[A-Za-z0-9]$")
REGEX_NUMERIC = re.compile(r"0[xX][0-9a-fA-F]+|[0-9]+")
REGEX_QUOTES = re.compile("(\"(.*?)\")")
def parse_options():
"""The user interface of this module."""
usage = "Run this tool to detect Kconfig symbols that are referenced but " \
"not defined in Kconfig. If no option is specified, " \
"checkkconfigsymbols defaults to check your current tree. " \
"Please note that specifying commits will 'git reset --hard\' " \
"your current tree! You may save uncommitted changes to avoid " \
"losing data."
parser = argparse.ArgumentParser(description=usage)
parser.add_argument('-c', '--commit', dest='commit', action='store',
default="",
help="check if the specified commit (hash) introduces "
"undefined Kconfig symbols")
parser.add_argument('-d', '--diff', dest='diff', action='store',
default="",
help="diff undefined symbols between two commits "
"(e.g., -d commmit1..commit2)")
parser.add_argument('-f', '--find', dest='find', action='store_true',
default=False,
help="find and show commits that may cause symbols to be "
"missing (required to run with --diff)")
parser.add_argument('-i', '--ignore', dest='ignore', action='store',
default="",
help="ignore files matching this Python regex "
"(e.g., -i '.*defconfig')")
parser.add_argument('-s', '--sim', dest='sim', action='store', default="",
help="print a list of max. 10 string-similar symbols")
parser.add_argument('--force', dest='force', action='store_true',
default=False,
help="reset current Git tree even when it's dirty")
parser.add_argument('--no-color', dest='color', action='store_false',
default=True,
help="don't print colored output (default when not "
"outputting to a terminal)")
args = parser.parse_args()
if args.commit and args.diff:
sys.exit("Please specify only one option at once.")
if args.diff and not re.match(r"^[\w\-\.\^]+\.\.[\w\-\.\^]+$", args.diff):
sys.exit("Please specify valid input in the following format: "
"\'commit1..commit2\'")
if args.commit or args.diff:
if not args.force and tree_is_dirty():
sys.exit("The current Git tree is dirty (see 'git status'). "
"Running this script may\ndelete important data since it "
"calls 'git reset --hard' for some performance\nreasons. "
" Please run this script in a clean Git tree or pass "
"'--force' if you\nwant to ignore this warning and "
"continue.")
if args.commit:
args.find = False
if args.ignore:
try:
re.match(args.ignore, "this/is/just/a/test.c")
except:
sys.exit("Please specify a valid Python regex.")
return args
def main():
"""Main function of this module."""
args = parse_options()
global COLOR
COLOR = args.color and sys.stdout.isatty()
if args.sim and not args.commit and not args.diff:
sims = find_sims(args.sim, args.ignore)
if sims:
print("%s: %s" % (yel("Similar symbols"), ', '.join(sims)))
else:
print("%s: no similar symbols found" % yel("Similar symbols"))
sys.exit(0)
# dictionary of (un)defined symbols
defined = {}
undefined = {}
if args.commit or args.diff:
head = get_head()
# get commit range
commit_a = None
commit_b = None
if args.commit:
commit_a = args.commit + "~"
commit_b = args.commit
elif args.diff:
split = args.diff.split("..")
commit_a = split[0]
commit_b = split[1]
undefined_a = {}
undefined_b = {}
# get undefined items before the commit
reset(commit_a)
undefined_a, _ = check_symbols(args.ignore)
# get undefined items for the commit
reset(commit_b)
undefined_b, defined = check_symbols(args.ignore)
# report cases that are present for the commit but not before
for symbol in sorted(undefined_b):
# symbol has not been undefined before
if symbol not in undefined_a:
files = sorted(undefined_b.get(symbol))
undefined[symbol] = files
# check if there are new files that reference the undefined symbol
else:
files = sorted(undefined_b.get(symbol) -
undefined_a.get(symbol))
if files:
undefined[symbol] = files
# reset to head
reset(head)
# default to check the entire tree
else:
undefined, defined = check_symbols(args.ignore)
# now print the output
for symbol in sorted(undefined):
print(red(symbol))
files = sorted(undefined.get(symbol))
print("%s: %s" % (yel("Referencing files"), ", ".join(files)))
sims = find_sims(symbol, args.ignore, defined)
sims_out = yel("Similar symbols")
if sims:
print("%s: %s" % (sims_out, ', '.join(sims)))
else:
print("%s: %s" % (sims_out, "no similar symbols found"))
if args.find:
print("%s:" % yel("Commits changing symbol"))
commits = find_commits(symbol, args.diff)
if commits:
for commit in commits:
commit = commit.split(" ", 1)
print("\t- %s (\"%s\")" % (yel(commit[0]), commit[1]))
else:
print("\t- no commit found")
print() # new line
def reset(commit):
"""Reset current git tree to %commit."""
execute(["git", "reset", "--hard", commit])
def yel(string):
"""
Color %string yellow.
"""
return "\033[33m%s\033[0m" % string if COLOR else string
def red(string):
"""
Color %string red.
"""
return "\033[31m%s\033[0m" % string if COLOR else string
def execute(cmd):
"""Execute %cmd and return stdout. Exit in case of error."""
try:
stdout = subprocess.check_output(cmd, stderr=subprocess.STDOUT, shell=False)
stdout = stdout.decode(errors='replace')
except subprocess.CalledProcessError as fail:
exit(fail)
return stdout
def find_commits(symbol, diff):
"""Find commits changing %symbol in the given range of %diff."""
commits = execute(["git", "log", "--pretty=oneline",
"--abbrev-commit", "-G",
symbol, diff])
return [x for x in commits.split("\n") if x]
def tree_is_dirty():
"""Return true if the current working tree is dirty (i.e., if any file has
been added, deleted, modified, renamed or copied but not committed)."""
stdout = execute(["git", "status", "--porcelain"])
for line in stdout:
if re.findall(r"[URMADC]{1}", line[:2]):
return True
return False
def get_head():
"""Return commit hash of current HEAD."""
stdout = execute(["git", "rev-parse", "HEAD"])
return stdout.strip('\n')
def partition(lst, size):
"""Partition list @lst into eveni-sized lists of size @size."""
return [lst[i::size] for i in range(size)]
def init_worker():
"""Set signal handler to ignore SIGINT."""
signal.signal(signal.SIGINT, signal.SIG_IGN)
def find_sims(symbol, ignore, defined=[]):
"""Return a list of max. ten Kconfig symbols that are string-similar to
@symbol."""
if defined:
return difflib.get_close_matches(symbol, set(defined), 10)
pool = Pool(cpu_count(), init_worker)
kfiles = []
for gitfile in get_files():
if REGEX_FILE_KCONFIG.match(gitfile):
kfiles.append(gitfile)
arglist = []
for part in partition(kfiles, cpu_count()):
arglist.append((part, ignore))
for res in pool.map(parse_kconfig_files, arglist):
defined.extend(res[0])
return difflib.get_close_matches(symbol, set(defined), 10)
def get_files():
"""Return a list of all files in the current git directory."""
# use 'git ls-files' to get the worklist
stdout = execute(["git", "ls-files"])
if len(stdout) > 0 and stdout[-1] == "\n":
stdout = stdout[:-1]
files = []
for gitfile in stdout.rsplit("\n"):
if ".git" in gitfile or "ChangeLog" in gitfile or \
".log" in gitfile or os.path.isdir(gitfile) or \
gitfile.startswith("tools/"):
continue
files.append(gitfile)
return files
def check_symbols(ignore):
"""Find undefined Kconfig symbols and return a dict with the symbol as key
and a list of referencing files as value. Files matching %ignore are not
checked for undefined symbols."""
pool = Pool(cpu_count(), init_worker)
try:
return check_symbols_helper(pool, ignore)
except KeyboardInterrupt:
pool.terminate()
pool.join()
sys.exit(1)
def check_symbols_helper(pool, ignore):
"""Helper method for check_symbols(). Used to catch keyboard interrupts in
check_symbols() in order to properly terminate running worker processes."""
source_files = []
kconfig_files = []
defined_symbols = []
referenced_symbols = dict() # {file: [symbols]}
for gitfile in get_files():
if REGEX_FILE_KCONFIG.match(gitfile):
kconfig_files.append(gitfile)
else:
if ignore and not re.match(ignore, gitfile):
continue
# add source files that do not match the ignore pattern
source_files.append(gitfile)
# parse source files
arglist = partition(source_files, cpu_count())
for res in pool.map(parse_source_files, arglist):
referenced_symbols.update(res)
# parse kconfig files
arglist = []
for part in partition(kconfig_files, cpu_count()):
arglist.append((part, ignore))
for res in pool.map(parse_kconfig_files, arglist):
defined_symbols.extend(res[0])
referenced_symbols.update(res[1])
defined_symbols = set(defined_symbols)
# inverse mapping of referenced_symbols to dict(symbol: [files])
inv_map = dict()
for _file, symbols in referenced_symbols.items():
for symbol in symbols:
inv_map[symbol] = inv_map.get(symbol, set())
inv_map[symbol].add(_file)
referenced_symbols = inv_map
undefined = {} # {symbol: [files]}
for symbol in sorted(referenced_symbols):
# filter some false positives
if symbol == "FOO" or symbol == "BAR" or \
symbol == "FOO_BAR" or symbol == "XXX":
continue
if symbol not in defined_symbols:
if symbol.endswith("_MODULE"):
# avoid false positives for kernel modules
if symbol[:-len("_MODULE")] in defined_symbols:
continue
undefined[symbol] = referenced_symbols.get(symbol)
return undefined, defined_symbols
def parse_source_files(source_files):
"""Parse each source file in @source_files and return dictionary with source
files as keys and lists of references Kconfig symbols as values."""
referenced_symbols = dict()
for sfile in source_files:
referenced_symbols[sfile] = parse_source_file(sfile)
return referenced_symbols
def parse_source_file(sfile):
"""Parse @sfile and return a list of referenced Kconfig symbols."""
lines = []
references = []
if not os.path.exists(sfile):
return references
with open(sfile, "r", encoding='utf-8', errors='replace') as stream:
lines = stream.readlines()
for line in lines:
if "CONFIG_" not in line:
continue
symbols = REGEX_SOURCE_SYMBOL.findall(line)
for symbol in symbols:
if not REGEX_FILTER_SYMBOLS.search(symbol):
continue
references.append(symbol)
return references
def get_symbols_in_line(line):
"""Return mentioned Kconfig symbols in @line."""
return REGEX_SYMBOL.findall(line)
def parse_kconfig_files(args):
"""Parse kconfig files and return tuple of defined and references Kconfig
symbols. Note, @args is a tuple of a list of files and the @ignore
pattern."""
kconfig_files = args[0]
ignore = args[1]
defined_symbols = []
referenced_symbols = dict()
for kfile in kconfig_files:
defined, references = parse_kconfig_file(kfile)
defined_symbols.extend(defined)
if ignore and re.match(ignore, kfile):
# do not collect references for files that match the ignore pattern
continue
referenced_symbols[kfile] = references
return (defined_symbols, referenced_symbols)
def parse_kconfig_file(kfile):
"""Parse @kfile and update symbol definitions and references."""
lines = []
defined = []
references = []
skip = False
if not os.path.exists(kfile):
return defined, references
with open(kfile, "r", encoding='utf-8', errors='replace') as stream:
lines = stream.readlines()
for i in range(len(lines)):
line = lines[i]
line = line.strip('\n')
line = line.split("#")[0] # ignore comments
if REGEX_KCONFIG_DEF.match(line):
symbol_def = REGEX_KCONFIG_DEF.findall(line)
defined.append(symbol_def[0])
skip = False
elif REGEX_KCONFIG_HELP.match(line):
skip = True
elif skip:
# ignore content of help messages
pass
elif REGEX_KCONFIG_STMT.match(line):
line = REGEX_QUOTES.sub("", line)
symbols = get_symbols_in_line(line)
# multi-line statements
while line.endswith("\\"):
i += 1
line = lines[i]
line = line.strip('\n')
symbols.extend(get_symbols_in_line(line))
for symbol in set(symbols):
if REGEX_NUMERIC.match(symbol):
# ignore numeric values
continue
references.append(symbol)
return defined, references
if __name__ == "__main__":
main()
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