modified poll() patch

modified poll() patch

[Boris Schaeling]

[-- Attachment #1: Type: text/plain, Size: 722 bytes --]

Here is the new poll() patch. Now invalid descriptors are recognized
(invalid = positive descriptors including 0 which are not open). If there
are invalid descriptors poll() returns immediately with the count of invalid
descriptors. The timer value is ignored. That's the way Linux handles this
case.

As far as I can see there is only one bug left in this poll() function: If a
descriptor is closed revents is set to POLLIN and not to POLLHUP. That's the
way previous poll() functions worked, too. This shouldn't be a problem as
read() will return 0 and tell the application that the socket can be closed.

I changed the test case, too (see polltest2.c). Hopefully this poll()
doesn't cause any problems any more.

Boris

[-- Attachment #2: newpoll2.cc --]
[-- Type: application/octet-stream, Size: 2801 bytes --]

/* poll.cc. Implements poll(2) via usage of select(2) call.

   Copyright 2000, 2001 Red Hat, Inc.

   This file is part of Cygwin.

   This software is a copyrighted work licensed under the terms of the
   Cygwin license.  Please consult the file "CYGWIN_LICENSE" for
   details. */

#include "winsup.h"
#include <sys/time.h>
#include <sys/poll.h>
#include <errno.h>
#include <stdlib.h>
#include "security.h"
#include "fhandler.h"
#include "path.h"
#include "dtable.h"
#include "cygerrno.h"
#include "cygheap.h"
#include "sigproc.h"

extern "C"
int
poll (struct pollfd *fds, unsigned int nfds, int timeout)
{
  int max_fd = 0;
  fd_set *read_fds, *write_fds, *except_fds;
  struct timeval tv = { timeout / 1000, (timeout % 1000) * 1000 };
  sigframe thisframe (mainthread);

  for (unsigned int i = 0; i < nfds; ++i)
    if (fds[i].fd > max_fd)
      max_fd = fds[i].fd;

  size_t fds_size = howmany(max_fd + 1, NFDBITS) * sizeof (fd_mask);

  read_fds = (fd_set *) alloca (fds_size);
  write_fds = (fd_set *) alloca (fds_size);
  except_fds = (fd_set *) alloca (fds_size);

  if (!read_fds || !write_fds || !except_fds)
    {
      set_errno (ENOMEM);
      return -1;
    }

  memset (read_fds, 0, fds_size);
  memset (write_fds, 0, fds_size);
  memset (except_fds, 0, fds_size);

  int invalid_fds = 0; 
  for (unsigned int i = 0; i < nfds; ++i) 
    { 
      fds[i].revents = 0; 
      if (!cygheap->fdtab.not_open(fds[i].fd)) 
        { 
          if (fds[i].events & POLLIN) 
            FD_SET(fds[i].fd, read_fds); 
          if (fds[i].events & POLLOUT) 
            FD_SET(fds[i].fd, write_fds); 
          if (fds[i].events & POLLPRI) 
            FD_SET(fds[i].fd, except_fds); 
        } 
      else if (fds[i].fd >= 0) 
        { 
          ++invalid_fds; 
          fds[i].revents = POLLNVAL; 
        } 
    } 

  if (invalid_fds) 
    return invalid_fds; 

  int ret = cygwin_select (max_fd + 1, read_fds, write_fds, except_fds, timeout < 0 ? NULL : &tv); 

  if (ret > 0) 
    for (unsigned int i = 0; i < nfds; ++i) 
      { 
        if (fds[i].fd >= 0) 
          { 
            if (cygheap->fdtab.not_open(fds[i].fd)) 
              fds[i].revents = POLLHUP; 
            else 
              { 
                if (FD_ISSET(fds[i].fd, read_fds)) 
                  fds[i].revents |= POLLIN; 
                if (FD_ISSET(fds[i].fd, write_fds)) 
                  fds[i].revents |= POLLOUT; 
                if (FD_ISSET(fds[i].fd, read_fds) && FD_ISSET(fds[i].fd, write_fds)) 
                  fds[i].revents |= POLLERR; 
                if (FD_ISSET(fds[i].fd, except_fds)) 
                  fds[i].revents |= POLLPRI; 
              } 
          } 
      } 

  return ret; 
} 

[-- Attachment #3: poll.patch2 --]
[-- Type: application/octet-stream, Size: 3759 bytes --]

--- poll.cc	Thu Nov 15 04:25:52 2001
+++ newpoll2.cc	Sat Mar 16 02:06:24 2002
@@ -26,7 +26,7 @@ int
 poll (struct pollfd *fds, unsigned int nfds, int timeout)
 {
   int max_fd = 0;
-  fd_set *open_fds, *read_fds, *write_fds, *except_fds;
+  fd_set *read_fds, *write_fds, *except_fds;
   struct timeval tv = { timeout / 1000, (timeout % 1000) * 1000 };
   sigframe thisframe (mainthread);
 
@@ -36,63 +36,65 @@ poll (struct pollfd *fds, unsigned int n
 
   size_t fds_size = howmany(max_fd + 1, NFDBITS) * sizeof (fd_mask);
 
-  open_fds = (fd_set *) alloca (fds_size);
   read_fds = (fd_set *) alloca (fds_size);
   write_fds = (fd_set *) alloca (fds_size);
   except_fds = (fd_set *) alloca (fds_size);
 
-  if (!open_fds || !read_fds || !write_fds || !except_fds)
+  if (!read_fds || !write_fds || !except_fds)
     {
       set_errno (ENOMEM);
       return -1;
     }
 
-  memset (open_fds, 0, fds_size);
   memset (read_fds, 0, fds_size);
   memset (write_fds, 0, fds_size);
   memset (except_fds, 0, fds_size);
 
-  bool valid_fds = false;
-  for (unsigned int i = 0; i < nfds; ++i)
-    if (!cygheap->fdtab.not_open (fds[i].fd))
-      {
-	valid_fds = true;
-	fds[i].revents = 0;
-	FD_SET (fds[i].fd, open_fds);
-	if (fds[i].events & POLLIN)
-	  FD_SET (fds[i].fd, read_fds);
-	if (fds[i].events & POLLOUT)
-	  FD_SET (fds[i].fd, write_fds);
-	if (fds[i].events & POLLPRI)
-	  FD_SET (fds[i].fd, except_fds);
-      }
-      else
-	fds[i].revents = POLLNVAL;
-
-  int ret = 0;
-  if (valid_fds)
-    ret = cygwin_select (max_fd + 1, read_fds, write_fds, except_fds,
-			 timeout < 0 ? NULL : &tv);
-
-  for (unsigned int i = 0; i < nfds; ++i)
-    {
-      if (fds[i].revents == POLLNVAL && ret >= 0)
-	ret++;
-      else if (cygheap->fdtab.not_open(fds[i].fd))
-	fds[i].revents = POLLHUP;
-      else if (ret < 0)
-	fds[i].revents = POLLERR;
-      else
-	{
-	  fds[i].revents = 0;
-	  if (FD_ISSET (fds[i].fd, read_fds))
-	    fds[i].revents |= POLLIN;
-	  if (FD_ISSET (fds[i].fd, write_fds))
-	    fds[i].revents |= POLLOUT;
-	  if (FD_ISSET (fds[i].fd, except_fds))
-	    fds[i].revents |= POLLPRI;
-	}
-    }
+  int invalid_fds = 0; 
+  for (unsigned int i = 0; i < nfds; ++i) 
+    { 
+      fds[i].revents = 0; 
+      if (!cygheap->fdtab.not_open(fds[i].fd)) 
+        { 
+          if (fds[i].events & POLLIN) 
+            FD_SET(fds[i].fd, read_fds); 
+          if (fds[i].events & POLLOUT) 
+            FD_SET(fds[i].fd, write_fds); 
+          if (fds[i].events & POLLPRI) 
+            FD_SET(fds[i].fd, except_fds); 
+        } 
+      else if (fds[i].fd >= 0) 
+        { 
+          ++invalid_fds; 
+          fds[i].revents = POLLNVAL; 
+        } 
+    } 
+
+  if (invalid_fds) 
+    return invalid_fds; 
+
+  int ret = cygwin_select (max_fd + 1, read_fds, write_fds, except_fds, timeout < 0 ? NULL : &tv); 
+
+  if (ret > 0) 
+    for (unsigned int i = 0; i < nfds; ++i) 
+      { 
+        if (fds[i].fd >= 0) 
+          { 
+            if (cygheap->fdtab.not_open(fds[i].fd)) 
+              fds[i].revents = POLLHUP; 
+            else 
+              { 
+                if (FD_ISSET(fds[i].fd, read_fds)) 
+                  fds[i].revents |= POLLIN; 
+                if (FD_ISSET(fds[i].fd, write_fds)) 
+                  fds[i].revents |= POLLOUT; 
+                if (FD_ISSET(fds[i].fd, read_fds) && FD_ISSET(fds[i].fd, write_fds)) 
+                  fds[i].revents |= POLLERR; 
+                if (FD_ISSET(fds[i].fd, except_fds)) 
+                  fds[i].revents |= POLLPRI; 
+              } 
+          } 
+      } 
 
-  return ret;
-}
+  return ret; 
+} 
\ No newline at end of file

[-- Attachment #4: polltest2.c --]
[-- Type: application/octet-stream, Size: 1336 bytes --]

/* gcc -opolltest2 polltest2.c */ 

#include <stdio.h> 
#include <string.h> 
#include <poll.h> 
#include <signal.h> 
#include <unistd.h> 

void callback_alarm(int sig) { return; } 

int main() 
{ 
	struct pollfd p[3]; 

	memset(p, 0, sizeof(struct pollfd) * 3); 

	p[0].fd = -1; 
	p[1].fd = -1; 
	p[2].fd = -1; 

	printf("all descriptors are negative - poll() must wait for 2 seconds\n"); 
	poll(p, 3, 2000); 
	printf("all descriptors are negative - revents for any descriptor must be 0: %d, %d, %d\n", p[0].revents, p[1].revents, p[2].revents); 

	p[2].fd = 0; 
	printf("no descriptor is ready - poll() must return 0: %d\n", poll(p, 3, 500)); 
	printf("no descriptor is ready - revents for any descriptor must be 0: %d, %d, %d\n", p[0].revents, p[1].revents, p[2].revents); 

	signal(SIGALRM, callback_alarm); 

	alarm(1); 

	printf("SIGALRM - poll() must return -1: %d\n", poll(p, 3, 1500)); 
	printf("SIGALRM - revents for any descriptor must be 0: %d, %d, %d\n", p[0].revents, p[1].revents, p[2].revents); 

	p[1].fd = 1000; 
	p[2].fd = 1001; 
	printf("2 descriptors are invalid - poll() must return 2 immediately: %d\n", poll(p, 3, 10000)); 
	printf("2 descriptors are invalid - revents must be POLLNVAL for 2. and 3. descriptor: %d, %d, %d\n", p[0].revents, p[1].revents, p[2].revents); 
}

[-- Attachment #5: Type: text/plain, Size: 214 bytes --]

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Re: modified poll() patch

[Corinna Vinschen]

On Sat, Mar 16, 2002 at 02:56:37PM +0100, Boris Schaeling wrote:
> Here is the new poll() patch. Now invalid descriptors are recognized

Boris,

thanks for the patch but could you please send a diff related to
the latest from current cvs?  I didn't back out your patch since
I'd waited for your correction.  This means, I can't apply your
patch cleanly.

Please send the new patch file and a ChangeLog entry (you know the
rules) briefly describing just the changes since your previous version.

Thanks,
Corinna

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AW: modified poll() patch

[Boris Schaeling]

[-- Attachment #1: Type: text/plain, Size: 439 bytes --]



> -----Ursprüngliche Nachricht-----
> Von: cygwin-owner@cygwin.com [mailto:cygwin-owner@cygwin.com]Im Auftrag
> von Corinna Vinschen
> Gesendet: Dienstag, 19. März 2002 11:55
> An: cygwin@cygwin.com
> Betreff: Re: modified poll() patch

> [...]
> thanks for the patch but could you please send a diff related to
> the latest from current cvs?  I didn't back out your patch since

Hi Corinna,

I've attached patch and changelog.

Boris

[-- Attachment #2: change.log2 --]
[-- Type: application/octet-stream, Size: 173 bytes --]

2002-03-19  Boris Schaeling  <boriss@web.de> 

	* poll.cc: add support for invalid descriptors 
	(invalid means positive descriptors including 0 
	which are not open) 

[-- Attachment #3: poll.patch2 --]
[-- Type: application/octet-stream, Size: 2620 bytes --]

--- poll.cc	Tue Mar 19 13:23:26 2002
+++ newpoll2.cc	Sat Mar 16 02:06:24 2002
@@ -50,41 +50,51 @@ poll (struct pollfd *fds, unsigned int n
   memset (write_fds, 0, fds_size);
   memset (except_fds, 0, fds_size);
 
+  int invalid_fds = 0; 
   for (unsigned int i = 0; i < nfds; ++i) 
     { 
       fds[i].revents = 0; 
       if (!cygheap->fdtab.not_open(fds[i].fd)) 
-	{ 
-	  if (fds[i].events & POLLIN) 
-	    FD_SET(fds[i].fd, read_fds); 
-	  if (fds[i].events & POLLOUT) 
-	    FD_SET(fds[i].fd, write_fds); 
-	  if (fds[i].events & POLLPRI) 
-	    FD_SET(fds[i].fd, except_fds); 
-	} 
+        { 
+          if (fds[i].events & POLLIN) 
+            FD_SET(fds[i].fd, read_fds); 
+          if (fds[i].events & POLLOUT) 
+            FD_SET(fds[i].fd, write_fds); 
+          if (fds[i].events & POLLPRI) 
+            FD_SET(fds[i].fd, except_fds); 
+        } 
+      else if (fds[i].fd >= 0) 
+        { 
+          ++invalid_fds; 
+          fds[i].revents = POLLNVAL; 
+        } 
     } 
 
-  int ret = cygwin_select (max_fd + 1, read_fds, write_fds, except_fds, timeout < 0 ? NULL : &tv);
+  if (invalid_fds) 
+    return invalid_fds; 
+
+  int ret = cygwin_select (max_fd + 1, read_fds, write_fds, except_fds, timeout < 0 ? NULL : &tv); 
 
   if (ret > 0) 
     for (unsigned int i = 0; i < nfds; ++i) 
       { 
-	if (fds[i].fd < 0) 
-	  fds[i].revents = POLLNVAL; 
-	else if (cygheap->fdtab.not_open(fds[i].fd)) 
-	  fds[i].revents = POLLHUP; 
-	else 
-	  { 
-	    if (FD_ISSET(fds[i].fd, read_fds)) 
-	      fds[i].revents |= POLLIN; 
-	    if (FD_ISSET(fds[i].fd, write_fds)) 
-	      fds[i].revents |= POLLOUT; 
-	    if (FD_ISSET(fds[i].fd, read_fds) && FD_ISSET(fds[i].fd, write_fds)) 
-	      fds[i].revents |= POLLERR; 
-	    if (FD_ISSET(fds[i].fd, except_fds)) 
-	      fds[i].revents |= POLLPRI; 
-	  } 
+        if (fds[i].fd >= 0) 
+          { 
+            if (cygheap->fdtab.not_open(fds[i].fd)) 
+              fds[i].revents = POLLHUP; 
+            else 
+              { 
+                if (FD_ISSET(fds[i].fd, read_fds)) 
+                  fds[i].revents |= POLLIN; 
+                if (FD_ISSET(fds[i].fd, write_fds)) 
+                  fds[i].revents |= POLLOUT; 
+                if (FD_ISSET(fds[i].fd, read_fds) && FD_ISSET(fds[i].fd, write_fds)) 
+                  fds[i].revents |= POLLERR; 
+                if (FD_ISSET(fds[i].fd, except_fds)) 
+                  fds[i].revents |= POLLPRI; 
+              } 
+          } 
       } 
 
   return ret; 
-} 
+} 
\ No newline at end of file


[-- Attachment #4: Type: text/plain, Size: 214 bytes --]

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Re: modified poll() patch

[Corinna Vinschen]

On Tue, Mar 19, 2002 at 01:35:51PM +0100, Boris Schaeling wrote:
> 
> 
> > -----Ursprüngliche Nachricht-----
> > Von: cygwin-owner@cygwin.com [mailto:cygwin-owner@cygwin.com]Im Auftrag
> > von Corinna Vinschen
> > Gesendet: Dienstag, 19. März 2002 11:55
> > An: cygwin@cygwin.com
> > Betreff: Re: modified poll() patch
> 
> > [...]
> > thanks for the patch but could you please send a diff related to
> > the latest from current cvs?  I didn't back out your patch since
> 
> Hi Corinna,
> 
> I've attached patch and changelog.

Thanks, applied.  I had to change the ChangeLog, though...

Corinna

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Red Hat, Inc.

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Re: modified poll() patch

[Jason Tishler]

Boris,

On Tue, Mar 19, 2002 at 06:14:13PM +0100, Corinna Vinschen wrote:
> On Tue, Mar 19, 2002 at 01:35:51PM +0100, Boris Schaeling wrote:
> > > thanks for the patch but could you please send a diff related to
> > > the latest from current cvs?  I didn't back out your patch since
> > 
> > I've attached patch and changelog.
> 
> Thanks, applied.  I had to change the ChangeLog, though...

I just checked that poll() in the latest snapshot does not hang.  Thanks
for making this change.

Jason

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