From 9c761cddaddeec4a6f491ca4525f9474d98317be Mon Sep 17 00:00:00 2001 From: jgoerzen Date: Mon, 6 Jan 2003 22:58:29 +0100 Subject: [PATCH] /offlineimap/head: changeset 314 More locking updates. Introduced a new MultiLock to threadutil. This lock will let a single thread acquire the same lock more than once, keeping track of how many times this happens, and will release the actual lock only when the lock's lock count gets back to zero. By using MultiLock, various functions in Curses.py and Blinkenlights.py no longer need to pass around to other functions a parameter indicating whether or not a lock should be obtained. This was a large cause of complexity and errors, which is now eliminated. Everything seems to be working properly wrt locking at this point. The Curses.Blinkenlights interface has achieved basic working functionality. --- offlineimap/head/offlineimap/threadutil.py | 51 +++++++ .../head/offlineimap/ui/Blinkenlights.py | 18 ++- offlineimap/head/offlineimap/ui/Curses.py | 135 +++++++++++------- offlineimap/head/offlineimap/ui/debuglock.py | 18 ++- 4 files changed, 155 insertions(+), 67 deletions(-) diff --git a/offlineimap/head/offlineimap/threadutil.py b/offlineimap/head/offlineimap/threadutil.py index 48fab97..3e01718 100644 --- a/offlineimap/head/offlineimap/threadutil.py +++ b/offlineimap/head/offlineimap/threadutil.py @@ -236,3 +236,54 @@ class InstanceLimitedThread(ExitNotifyThread): instancelimitedsems[self.instancename].release() +###################################################################### +# Multi-lock -- capable of handling a single thread requesting a lock +# multiple times +###################################################################### + +class MultiLock: + def __init__(self): + self.lock = Lock() + self.statuslock = Lock() + self.locksheld = {} + + def acquire(self): + """Obtain a lock. Provides nice support for a single + thread trying to lock it several times -- as may be the case + if one I/O-using object calls others, while wanting to make it all + an atomic operation. Keeps a "lock request count" for the current + thread, and acquires the lock when it goes above zero, releases when + it goes below one. + + This call is always blocking.""" + + # First, check to see if this thread already has a lock. + # If so, increment the lock count and just return. + self.statuslock.acquire() + try: + threadid = thread.get_ident() + + if threadid in self.locksheld: + self.locksheld[threadid] += 1 + return + else: + # This is safe because it is a per-thread structure + self.locksheld[threadid] = 1 + finally: + self.statuslock.release() + self.lock.acquire() + + def release(self): + self.statuslock.acquire() + try: + threadid = thread.get_ident() + if self.locksheld[threadid] > 1: + self.locksheld[threadid] -= 1 + return + else: + del self.locksheld[threadid] + self.lock.release() + finally: + self.statuslock.release() + + diff --git a/offlineimap/head/offlineimap/ui/Blinkenlights.py b/offlineimap/head/offlineimap/ui/Blinkenlights.py index b87cacc..08b583c 100644 --- a/offlineimap/head/offlineimap/ui/Blinkenlights.py +++ b/offlineimap/head/offlineimap/ui/Blinkenlights.py @@ -19,6 +19,7 @@ from threading import * from offlineimap.ui.UIBase import UIBase import thread +from offlineimap.threadutil import MultiLock from debuglock import DebuggingLock @@ -75,7 +76,7 @@ class BlinkenBase: def init_banner(s): s.availablethreadframes = {} s.threadframes = {} - s.tflock = DebuggingLock('tflock') + s.tflock = MultiLock() def threadExited(s, thread): threadid = thread.threadid @@ -92,12 +93,11 @@ class BlinkenBase: UIBase.threadExited(s, thread) - def gettf(s, lock = 1): + def gettf(s): threadid = thread.get_ident() accountname = s.getthreadaccount() - if lock: - s.tflock.acquire() + s.tflock.acquire() try: if not accountname in s.threadframes: @@ -111,14 +111,12 @@ class BlinkenBase: if len(s.availablethreadframes[accountname]): tf = s.availablethreadframes[accountname].pop(0) - tf.setthread(currentThread(), lock) + tf.setthread(currentThread()) else: - tf = s.getaccountframe().getnewthreadframe(lock) + tf = s.getaccountframe().getnewthreadframe() s.threadframes[accountname][threadid] = tf return tf - finally: - if lock: - s.tflock.release() - + s.tflock.release() + diff --git a/offlineimap/head/offlineimap/ui/Curses.py b/offlineimap/head/offlineimap/ui/Curses.py index ac26ef9..c528cf1 100644 --- a/offlineimap/head/offlineimap/ui/Curses.py +++ b/offlineimap/head/offlineimap/ui/Curses.py @@ -19,7 +19,9 @@ from Blinkenlights import BlinkenBase from UIBase import UIBase from threading import * +import thread from offlineimap import version, threadutil +from offlineimap.threadutil import MultiLock import curses, curses.panel, curses.textpad, curses.wrapper from debuglock import DebuggingLock @@ -31,6 +33,27 @@ class CursesUtil: self.start() self.nextpair = 1 self.pairlock = Lock() + self.iolock = MultiLock() + + def lock(self): + self.iolock.acquire() + + def unlock(self): + self.iolock.release() + + def locked(self, target, *args, **kwargs): + """Perform an operation with full locking.""" + self.lock() + try: + apply(target, args, kwargs) + finally: + self.unlock() + + def refresh(self): + def lockedstuff(): + curses.panel.update_panels() + curses.doupdate() + self.locked(lockedstuff) def isactive(self): return hasattr(self, 'stdscr') @@ -85,31 +108,29 @@ class CursesUtil: self.start() class CursesAccountFrame: - def __init__(s, master, accountname, iolock): - s.iolock = iolock + def __init__(s, master, accountname): s.c = master s.children = [] s.accountname = accountname - def setwindow(s, window, lock = 1): + def setwindow(s, window): s.window = window acctstr = '%15.15s: ' % s.accountname s.window.addstr(0, 0, acctstr) s.location = len(acctstr) for child in s.children: - child.update(window, 0, s.location, lock) + child.update(window, 0, s.location) s.location += 1 - def getnewthreadframe(s, lock = 1): - tf = CursesThreadFrame(s.c, s.window, 0, s.location, s.iolock, lock) + def getnewthreadframe(s): + tf = CursesThreadFrame(s.c, s.window, 0, s.location) s.location += 1 s.children.append(tf) return tf class CursesThreadFrame: - def __init__(s, master, window, y, x, iolock, lock = 1): + def __init__(s, master, window, y, x): """master should be a CursesUtil object.""" - s.iolock = iolock s.c = master s.window = window s.x = x @@ -128,34 +149,30 @@ class CursesThreadFrame: 'yellow': curses.A_BOLD | s.c.getpair(curses.COLOR_YELLOW, bg), 'pink': curses.A_BOLD | s.c.getpair(curses.COLOR_RED, bg)} #s.setcolor('gray') - s.setcolor('black', lock) + s.setcolor('black') - def setcolor(self, color, lock = 1): + def setcolor(self, color): self.color = self.colormap[color] - self.display(lock) + self.display() - def display(self, lock = 1): - if lock: - self.iolock.acquire() - try: + def display(self): + def lockedstuff(): self.window.addstr(self.y, self.x, '.', self.color) self.c.stdscr.move(self.c.height - 1, self.c.width - 1) self.window.refresh() - finally: - if lock: - self.iolock.release() + self.c.locked(lockedstuff) def getcolor(self): return self.color - def update(self, window, y, x, lock = 1): + def update(self, window, y, x): self.window = window self.y = y self.x = x - self.display(lock) + self.display() - def setthread(self, newthread, lock = 1): - self.setcolor('black', lock) + def setthread(self, newthread): + self.setcolor('black') #if newthread: # self.setcolor('gray') #else: @@ -234,13 +251,12 @@ class InputHandler: class Blinkenlights(BlinkenBase, UIBase): def init_banner(s): - s.iolock = DebuggingLock('iolock') s.af = {} s.aflock = DebuggingLock('aflock') s.c = CursesUtil() s.text = [] BlinkenBase.init_banner(s) - s.setupwindows(dolock = 0) + s.setupwindows() s.inputhandler = InputHandler(s.c) s.gettf().setcolor('red') s._msg(version.banner) @@ -251,22 +267,26 @@ class Blinkenlights(BlinkenBase, UIBase): def getpass(s, accountname, config, errmsg = None): s.inputhandler.input_acquire() - s.iolock.acquire() + + # See comment on _msg for info on why both locks are obtained. + + s.tflock.acquire() + s.c.lock() try: - s.gettf(lock = 0).setcolor('white', lock = 0) - s._addline_unlocked(" *** Input Required", s.gettf().getcolor()) - s._addline_unlocked(" *** Please enter password for account %s: " % accountname, - s.gettf(lock = 0).getcolor()) + s.gettf().setcolor('white') + s._addline(" *** Input Required", s.gettf().getcolor()) + s._addline(" *** Please enter password for account %s: " % accountname, + s.gettf().getcolor()) s.logwindow.refresh() password = s.logwindow.getstr() finally: - s.iolock.release() + s.tflock.release() + s.c.unlock() s.inputhandler.input_release() return password - def setupwindows(s, dolock = 1): - if dolock: - s.iolock.acquire() + def setupwindows(s): + s.c.lock() try: s.bannerwindow = curses.newwin(1, s.c.width, 0, 0) s.setupwindow_drawbanner() @@ -282,13 +302,12 @@ class Blinkenlights(BlinkenBase, UIBase): pos = s.c.height - 1 for account in accounts: accountwindow = curses.newwin(1, s.c.width, pos, 0) - s.af[account].setwindow(accountwindow, lock = 0) + s.af[account].setwindow(accountwindow) pos -= 1 curses.doupdate() finally: - if dolock: - s.iolock.release() + s.c.unlock() def setupwindow_drawbanner(s): s.bannerwindow.bkgd(' ', curses.A_BOLD | \ @@ -315,11 +334,13 @@ class Blinkenlights(BlinkenBase, UIBase): return s.af[accountname] # New one. - s.af[accountname] = CursesAccountFrame(s.c, accountname, s.iolock) - s.iolock.acquire() - s.c.reset() - s.setupwindows(dolock = 0) - s.iolock.release() + s.af[accountname] = CursesAccountFrame(s.c, accountname) + s.c.lock() + try: + s.c.reset() + s.setupwindows() + finally: + s.c.unlock() finally: s.aflock.release() return s.af[accountname] @@ -330,25 +351,37 @@ class Blinkenlights(BlinkenBase, UIBase): for thisline in msg.split("\n"): s._msg(thisline) return - s.iolock.acquire() + + # We must acquire both locks. Otherwise, deadlock can result. + # This can happen if one thread calls _msg (locking curses, then + # tf) and another tries to set the color (locking tf, then curses) + # + # By locking both up-front here, in this order, we prevent deadlock. + + s.tflock.acquire() + s.c.lock() try: if not s.c.isactive(): # For dumping out exceptions and stuff. print msg return if color: - s.gettf(lock = 0).setcolor(color, lock = 0) - s._addline_unlocked(msg, s.gettf(lock = 0).getcolor()) + s.gettf().setcolor(color) + s._addline(msg, s.gettf().getcolor()) s.logwindow.refresh() finally: - s.iolock.release() + s.c.unlock() + s.tflock.release() - def _addline_unlocked(s, msg, color): - s.logwindow.addstr(msg + "\n", color) - s.text.append((msg, color)) - while len(s.text) > s.logheight: - s.text = s.text[1:] - + def _addline(s, msg, color): + s.c.lock() + try: + s.logwindow.addstr(msg + "\n", color) + s.text.append((msg, color)) + while len(s.text) > s.logheight: + s.text = s.text[1:] + finally: + s.c.unlock() def terminate(s, exitstatus = 0): s.c.stop() diff --git a/offlineimap/head/offlineimap/ui/debuglock.py b/offlineimap/head/offlineimap/ui/debuglock.py index b884414..1f1ad22 100644 --- a/offlineimap/head/offlineimap/ui/debuglock.py +++ b/offlineimap/head/offlineimap/ui/debuglock.py @@ -19,6 +19,7 @@ from threading import * import traceback logfile = open("/tmp/logfile", "wt") +loglock = Lock() class DebuggingLock: def __init__(self, name): @@ -28,16 +29,21 @@ class DebuggingLock: def acquire(self, blocking = 1): self.print_tb("Acquire lock") self.lock.acquire(blocking) - logfile.write("===== %s: Thread %s acquired lock\n" % (self.name, currentThread().getName())) + self.logmsg("===== %s: Thread %s acquired lock\n" % (self.name, currentThread().getName())) def release(self): self.print_tb("Release lock") self.lock.release() - def print_tb(self, msg): - logfile.write("==== %s: Thread %s attempting to %s\n" % \ - (self.name, currentThread().getName(), msg)) - logfile.write("\n".join(traceback.format_list(traceback.extract_stack()))) - logfile.write("\n") + def logmsg(self, msg): + loglock.acquire() + logfile.write(msg + "\n") logfile.flush() + loglock.release() + + def print_tb(self, msg): + self.logmsg(".... %s: Thread %s attempting to %s\n" % \ + (self.name, currentThread().getName(), msg) + \ + "\n".join(traceback.format_list(traceback.extract_stack()))) + -- 2.39.2