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From: "teodori.serge at hotmail dot com" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sources.redhat.com
Subject: [Bug libc/13660] New: poll wrong revents returned
Date: Fri, 03 Feb 2012 19:14:00 -0000
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http://sourceware.org/bugzilla/show_bug.cgi?id=13660

             Bug #: 13660
           Summary: poll wrong revents returned
           Product: glibc
           Version: 2.14
            Status: NEW
          Severity: critical
          Priority: P2
         Component: libc
        AssignedTo: drepper.fsp@gmail.com
        ReportedBy: teodori.serge@hotmail.com
    Classification: Unclassified


Hello,
poll() is not returning the right events. If socket has data to read, POLLIN is
set, but if socket is closed or shutdown it also sets POLLIN? It should
normally be POLLERR POLLHUP or POLLNVAL, at least not POLLIN.

Ex.:

int prc = 0;
struct pollfd pfd;
while(prc != -1){
 pfd.fd = connectedsocket;
 pfd.events = POLLIN;
 prc = poll(&pfd, 1, 1000);
 if(prc == -1){
  perror("poll");
 }else if(prc == 0){
  printf("timeout");
 }else if(prc == 1 && pfd.revents == POLLIN){
  recv(pfd.fd, buff, sizeof(buff), 0);
  printf("data: %s\n", buff);
 }else if(prc == 1 && pfd.revents != POLLIN){
  close(pfd.fd);
  printf("socket closed\n");
  prc = -1;
 }
}

Output:
timeout
timeout
timeout
data: Hello //peer send data
timeout
timeout
timeout
data: // peer closed or shutdown socket -> poll is heating up 100% CPU
data:
data:
data:

This is the case on Ubuntu and on my own linux from scratch (linux-3.2.2 +
glibc-2.14.1 compiled with gcc-4.6.2 and the linux-3.2.2 headers).
I doubt that it could be and build error, because I tried it on i386 and x86
with different.

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