XrdPollE.icc

/******************************************************************************/
/*                                                                            */
/*                          X r d P o l l E . i c c                           */
/*                                                                            */
/* (c) 2008 by the Board of Trustees of the Leland Stanford, Jr., University  */
/*                            All Rights Reserved                             */
/*   Produced by Andrew Hanushevsky for Stanford University under contract    */
/*              DE-AC02-76-SFO0515 with the Department of Energy              */
/*                                                                            */
/* This file is part of the XRootD software suite.                            */
/*                                                                            */
/* XRootD is free software: you can redistribute it and/or modify it under    */
/* the terms of the GNU Lesser General Public License as published by the     */
/* Free Software Foundation, either version 3 of the License, or (at your     */
/* option) any later version.                                                 */
/*                                                                            */
/* XRootD is distributed in the hope that it will be useful, but WITHOUT      */
/* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or      */
/* FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public       */
/* License for more details.                                                  */
/*                                                                            */
/* You should have received a copy of the GNU Lesser General Public License   */
/* along with XRootD in a file called COPYING.LESSER (LGPL license) and file  */
/* COPYING (GPL license).  If not, see <http://www.gnu.org/licenses/>.        */
/*                                                                            */
/* The copyright holder's institutional names and contributor's names may not */
/* be used to endorse or promote products derived from this software without  */
/* specific prior written permission of the institution or contributor.       */
/******************************************************************************/

#ifndef __APPLE__
#include <malloc.h>
#endif
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/epoll.h>

#include "XrdSys/XrdSysError.hh"
#include "Xrd/XrdLink.hh"
#include "Xrd/XrdPollE.hh"
#include "Xrd/XrdScheduler.hh"
  
/******************************************************************************/
/*                             n e w P o l l e r                              */
/******************************************************************************/
  
XrdPoll *XrdPoll::newPoller(int pollid, int maxfd)
{
   int pfd, bytes, alignment, pagsz = getpagesize();
   struct epoll_event *pp;

// Open the /dev/poll driver
//
#ifndef EPOLL_CLOEXEC
   if ((pfd = epoll_create(maxfd)) >= 0) fcntl(pfd, F_SETFD, FD_CLOEXEC);
      else
#else
   if ((pfd = epoll_create1(EPOLL_CLOEXEC)) < 0)
#endif
      {XrdLog->Emsg("Poll", errno, "create epoll device"); return 0;}

// Calculate the size of the poll table and allocate it
//
   bytes     = maxfd * sizeof(struct epoll_event);
   alignment = (bytes < pagsz ? 1024 : pagsz);
   if (!(pp = (struct epoll_event *)memalign(alignment, bytes)))
      {XrdLog->Emsg("Poll", ENOMEM, "create poll table");
       close(pfd);
       return 0;
      }

// Create new poll object
//
   memset((void *)pp, 0, bytes);
   return (XrdPoll *)new XrdPollE(pp, maxfd, pfd);
}
 
/******************************************************************************/
/*                            D e s t r u c t o r                             */
/******************************************************************************/
  
XrdPollE::~XrdPollE()
{
   if (PollTab) free(PollTab);
   if (PollDfd >= 0) close(PollDfd);
}
  
/******************************************************************************/
/*                               D i s a b l e                                */
/******************************************************************************/

void XrdPollE::Disable(XrdLink *lp, const char *etxt)
{

// Simply return if the link is already disabled
//
   if (!lp->isEnabled) return;

// If Linux 2.6.9 we use EPOLLONESHOT to automatically disable a polled fd.
// So, the Disable() method need not do anything. Prior kernels did not have
// this mechanism so we need to do this manually.
//
#ifndef EPOLLONESHOT
   struct epoll_event myEvents = {0, (void *)lp};

// Enable this fd. Unlike solaris, epoll_ctl() does not block when the pollfd
// is being waited upon by another thread.
//
   if (epoll_ctl(PollDfd, EPOLL_CTL_MOD, lp->FDnum(), &myEvents))
      {XrdLog->Emsg("Poll", errno, "disable link", lp->ID); return;}
#endif

// Trace this event
//
   lp->isEnabled = 0;
   TRACEI(POLL, "Poller " <<PID <<" async disabling link " <<lp->FD);

// Check if this link needs to be rescheduled. If so, the caller better have
// the link opMutex lock held for this to work!
//
   if (etxt && Finish(lp, etxt)) XrdSched->Schedule((XrdJob *)lp);
}

/******************************************************************************/
/*                                E n a b l e                                 */
/******************************************************************************/

int XrdPollE::Enable(XrdLink *lp)
{
   struct epoll_event myEvents = {ePollEvents, {(void *)lp}};

// Simply return if the link is already enabled
//
   if (lp->isEnabled) return 1;

// Enable this fd. Unlike solaris, epoll_ctl() does not block when the pollfd
// is being waited upon by another thread.
//
   lp->isEnabled = 1;
   if (epoll_ctl(PollDfd, EPOLL_CTL_MOD, lp->FDnum(), &myEvents))
      {XrdLog->Emsg("Poll", errno, "enable link", lp->ID); 
       lp->isEnabled = 0;
       return 0;
      }

// Do final processing
//
   TRACE(POLL, "Poller " <<PID <<" enabled " <<lp->ID);
   numEnabled++;
   return 1;
}

/******************************************************************************/
/*                               E x c l u d e                                */
/******************************************************************************/
  
void XrdPollE::Exclude(XrdLink *lp)
{

// Make sure this link is not enabled
//
   if (lp->isEnabled) 
      {XrdLog->Emsg("Poll", "Detach of enabled link", lp->ID);
       Disable(lp);
      }
}

/******************************************************************************/
/*                               I n c l u d e                                */
/******************************************************************************/
  
int XrdPollE::Include(XrdLink *lp)
{
   struct epoll_event myEvent = {0, {(void *)lp}};
   int rc;

// Add this fd to the poll set
//
   if ((rc = epoll_ctl(PollDfd, EPOLL_CTL_ADD, lp->FDnum(), &myEvent)) < 0)
      XrdLog->Emsg("Poll", errno, "include link", lp->ID);

// All done
//
   return rc == 0;
}

/******************************************************************************/
/*                                 r e m F D                                  */
/******************************************************************************/
  
void XrdPollE::remFD(XrdLink *lp, unsigned int events)
{
   struct epoll_event myEvents = {0, {(void *)lp}};
   static const char *why;
   static char buff[32];

// It works out that ONESHOT mode or even CTL_MOD requests do not necessarily
// prevent epoll_wait() from returning on an error event. So, we must manually
// remove the fd from the set and assume the logic was actually correct. If it
// wasn't then the client will eventually timeout and retry the request.
//
   if (events & (EPOLLHUP | EPOLLRDHUP)) why = "Sever";
      else if (events & EPOLLERR) why = "Error";
              else why = "Disabled";
   snprintf(buff, sizeof(buff), "%s (%x)", why, events);
   XrdLog->Emsg("Poll", buff, "event occured for", lp->ID);

   if (epoll_ctl(PollDfd, EPOLL_CTL_DEL, lp->FDnum(), &myEvents))
      XrdLog->Emsg("Poll", errno, "exclude link", lp->ID);
}

/******************************************************************************/
/*                                 S t a r t                                  */
/******************************************************************************/
  
void XrdPollE::Start(XrdSysSemaphore *syncsem, int &retcode)
{
   char eBuff[64];
   int i, numpolled, num2sched;
   XrdJob *jfirst, *jlast;
   const short pollOK = EPOLLIN | EPOLLPRI;
   XrdLink *lp;

// Indicate to the starting thread that all went well
//
   retcode = 0;
   syncsem->Post();

// Now start dispatching links that are ready
//
   do {do {numpolled = epoll_wait(PollDfd, PollTab, PollMax, -1);}
          while (numpolled < 0 && errno == EINTR);
       if (numpolled == 0) continue;
       if (numpolled <  0)
          {XrdLog->Emsg("Poll", errno, "poll for events");
           abort();
          }
       numEvents += numpolled;

       // Checkout which links must be dispatched (no need to lock)
       //
       jfirst = jlast = 0; num2sched = 0;
       for (i = 0; i < numpolled; i++)
           {if ((lp = (XrdLink *)PollTab[i].data.ptr))
               if (!(lp->isEnabled)) remFD(lp, PollTab[i].events);
                  else {lp->isEnabled = 0;
                        if (!(PollTab[i].events & pollOK))
                           Finish(lp, x2Text(PollTab[i].events, eBuff));
                        lp->NextJob = jfirst; jfirst = (XrdJob *)lp;
                        if (!jlast) jlast=(XrdJob *)lp;
                        num2sched++;
#ifndef EPOLLONESHOT
                        PollTab[i].events  = 0;
                        if (epoll_ctl(PollDfd,EPOLL_CTL_MOD,lp->FDnum(),&PollTab[i]))
                           XrdLog->Emsg("Poll", errno, "disable link", lp->ID);
#endif
                       } else XrdLog->Emsg("Poll", "null link event!!!!");
           }

       // Schedule the polled links
       //
       if (num2sched == 1) XrdSched->Schedule(jfirst);
          else if (num2sched) XrdSched->Schedule(num2sched, jfirst, jlast);
      } while(1);
}

/******************************************************************************/
/*                                x 2 T e x t                                 */
/******************************************************************************/
  
const char *XrdPollE::x2Text(unsigned int events, char *buff)
{
   if (events & EPOLLERR) return "socket error";

   if (events & (EPOLLHUP | EPOLLRDHUP)) return "client disconnected";

   sprintf(buff, "unusual event (%.4x)", events);
   return buff;
}