upstream/mercurial-mirror Files · mercurial/pure/charencode.py

lock: fix race in lock-breaking code...

lock: fix race in lock-breaking code With low frequency, I see hg pulls fail with output like: abort: no such file or directory: .hg/store/lock I think what happens is, in lock.py, in: def _testlock(self, locker): if not self._lockshouldbebroken(locker): return locker # if locker dead, break lock. must do this with another lock # held, or can race and break valid lock. try: with lock(self.vfs, self.f + b'.break', timeout=0): self.vfs.unlink(self.f) except error.LockError: return locker if a lock is breakable on disk, and two hg processes concurrently get to the "if locker dead" comment, a possible interleaving is: process1 finishes executing the function and then process2 finishes executing the function. If that happens, process2 will either get ENOENT in self.vfs.unlink (resulting in the spurious failure above), or break a valid lock and potentially cause repository corruption. The fix is simple enough: make sure the lock is breakable _inside_ the critical section, because only then can we know that no other process can invalidate our knowledge on the lock on disk. I don't think there are tests for this. I've tested this manually with: diff --git a/mercurial/lock.py b/mercurial/lock.py --- a/mercurial/lock.py +++ b/mercurial/lock.py @@ -351,6 +351,8 @@ class lock(object): if not self._lockshouldbebroken(locker): return locker + import random + time.sleep(1. + random.random()) # if locker dead, break lock. must do this with another lock # held, or can race and break valid lock. try: @@ -358,6 +360,7 @@ class lock(object): self.vfs.unlink(self.f) except error.LockError: return locker + time.sleep(1) def testlock(self): """return id of locker if lock is valid, else None. and I see this change of behavior before/after this commit: $ $hg init repo $ cd repo $ ln -s $HOSTNAME/effffffc:987654321 .hg/wlock $ touch a $ $hg commit -Am_ & $hg commit -Am _; wait -abort: No such file or directory: '/tmp/repo/.hg/wlock' adding a +warning: ignoring unknown working parent 679a8959a8ca! +nothing changed Differential Revision: https://phab.mercurial-scm.org/D7199

Augie Fackler - - Load All Authors

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      # charencode.py - miscellaneous character encoding

      #

      #  Copyright 2005-2009 Matt Mackall <mpm@selenic.com> and others

      #

      # This software may be used and distributed according to the terms of the

      # GNU General Public License version 2 or any later version.

      from __future__ import absolute_import

      import array

      from .. import pycompat

      def isasciistr(s):

          try:

              s.decode('ascii')

              return True

          except UnicodeDecodeError:

              return False

      def asciilower(s):

          '''convert a string to lowercase if ASCII

          Raises UnicodeDecodeError if non-ASCII characters are found.'''

          s.decode('ascii')

          return s.lower()

      def asciiupper(s):

          '''convert a string to uppercase if ASCII

          Raises UnicodeDecodeError if non-ASCII characters are found.'''

          s.decode('ascii')

          return s.upper()

      _jsonmap = []

      _jsonmap.extend(b"\\u%04x" % x for x in range(32))

      _jsonmap.extend(pycompat.bytechr(x) for x in range(32, 127))

      _jsonmap.append(b'\\u007f')

      _jsonmap[0x09] = b'\\t'

      _jsonmap[0x0A] = b'\\n'

      _jsonmap[0x22] = b'\\"'

      _jsonmap[0x5C] = b'\\\\'

      _jsonmap[0x08] = b'\\b'

      _jsonmap[0x0C] = b'\\f'

      _jsonmap[0x0D] = b'\\r'

      _paranoidjsonmap = _jsonmap[:]

      _paranoidjsonmap[0x3C] = b'\\u003c'  # '<' (e.g. escape "</script>")

      _paranoidjsonmap[0x3E] = b'\\u003e'  # '>'

      _jsonmap.extend(pycompat.bytechr(x) for x in range(128, 256))

      def jsonescapeu8fast(u8chars, paranoid):

          """Convert a UTF-8 byte string to JSON-escaped form (fast path)

          Raises ValueError if non-ASCII characters have to be escaped.

          """

          if paranoid:

              jm = _paranoidjsonmap

          else:

              jm = _jsonmap

          try:

              return b''.join(jm[x] for x in bytearray(u8chars))

          except IndexError:

              raise ValueError

      if pycompat.ispy3:

          _utf8strict = r'surrogatepass'

      else:

          _utf8strict = r'strict'

      def jsonescapeu8fallback(u8chars, paranoid):

          """Convert a UTF-8 byte string to JSON-escaped form (slow path)

          Escapes all non-ASCII characters no matter if paranoid is False.

          """

          if paranoid:

              jm = _paranoidjsonmap

          else:

              jm = _jsonmap

          # non-BMP char is represented as UTF-16 surrogate pair

          u16b = u8chars.decode('utf-8', _utf8strict).encode('utf-16', _utf8strict)

          u16codes = array.array('H', u16b)

          u16codes.pop(0)  # drop BOM

          return b''.join(jm[x] if x < 128 else b'\\u%04x' % x for x in u16codes)

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				# charencode.py - miscellaneous character encoding
				#
				# Copyright 2005-2009 Matt Mackall <mpm@selenic.com> and others
				#
				# This software may be used and distributed according to the terms of the
				# GNU General Public License version 2 or any later version.

				from __future__ import absolute_import

				import array

				from .. import pycompat


				def isasciistr(s):
				try:
				s.decode('ascii')
				return True
				except UnicodeDecodeError:
				return False


				def asciilower(s):
				'''convert a string to lowercase if ASCII

				Raises UnicodeDecodeError if non-ASCII characters are found.'''
				s.decode('ascii')
				return s.lower()


				def asciiupper(s):
				'''convert a string to uppercase if ASCII

				Raises UnicodeDecodeError if non-ASCII characters are found.'''
				s.decode('ascii')
				return s.upper()


				_jsonmap = []
				_jsonmap.extend(b"\\u%04x" % x for x in range(32))
				_jsonmap.extend(pycompat.bytechr(x) for x in range(32, 127))
				_jsonmap.append(b'\\u007f')
				_jsonmap[0x09] = b'\\t'
				_jsonmap[0x0A] = b'\\n'
				_jsonmap[0x22] = b'\\"'
				_jsonmap[0x5C] = b'\\\\'
				_jsonmap[0x08] = b'\\b'
				_jsonmap[0x0C] = b'\\f'
				_jsonmap[0x0D] = b'\\r'
				_paranoidjsonmap = _jsonmap[:]
				_paranoidjsonmap[0x3C] = b'\\u003c' # '<' (e.g. escape "</script>")
				_paranoidjsonmap[0x3E] = b'\\u003e' # '>'
				_jsonmap.extend(pycompat.bytechr(x) for x in range(128, 256))


				def jsonescapeu8fast(u8chars, paranoid):
				"""Convert a UTF-8 byte string to JSON-escaped form (fast path)

				Raises ValueError if non-ASCII characters have to be escaped.
				"""
				if paranoid:
				jm = _paranoidjsonmap
				else:
				jm = _jsonmap
				try:
				return b''.join(jm[x] for x in bytearray(u8chars))
				except IndexError:
				raise ValueError


				if pycompat.ispy3:
				_utf8strict = r'surrogatepass'
				else:
				_utf8strict = r'strict'


				def jsonescapeu8fallback(u8chars, paranoid):
				"""Convert a UTF-8 byte string to JSON-escaped form (slow path)

				Escapes all non-ASCII characters no matter if paranoid is False.
				"""
				if paranoid:
				jm = _paranoidjsonmap
				else:
				jm = _jsonmap
				# non-BMP char is represented as UTF-16 surrogate pair
				u16b = u8chars.decode('utf-8', _utf8strict).encode('utf-16', _utf8strict)
				u16codes = array.array('H', u16b)
				u16codes.pop(0) # drop BOM
				return b''.join(jm[x] if x < 128 else b'\\u%04x' % x for x in u16codes)