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Hurd bug 22861: Do not select() exceptions from pipes.

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The GNU Hurd has a bug that can make select() report an exception in a
pipe even though none has actually occurred.  The typical result is
that ELinks closes the pipe through which it internally passes all
input events, such as keypresses.  It then no longer reacts to what
the user is trying to do.

Work around the Hurd bug by making set_handlers() check whether the
file descriptor refers to a pipe, and if so, pretend the caller did
not provide any handler for exceptions.  This is a minimal change that
avoids slowing down the select() loop itself and does not require
careful analysis of the callers to statically find out which file
descriptors might refer to pipes.  The extra stat() calls may slow
ELinks down somewhat, but anyway it'll work better than it did without
the patch, and if the Hurd bug is ever fixed, we can remove the
workaround at that time.
This commit is contained in:
Kalle Olavi Niemitalo 2008-09-07 22:30:40 +03:00 committed by Kalle Olavi Niemitalo
parent b94657869b
commit a0d624cd61
2 changed files with 20 additions and 0 deletions
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2
NEWS
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@ -30,6 +30,8 @@ includes the changes listed under "ELinks 0.11.4.GIT now" below.
SSL errors especially in HTTP POST requests using GnuTLS.
* bugs 1007, 1041: Display unrecognized lines in FTP directory
listings, instead of annoying the user with error messages.
* Hurd bug 22861: Work around select() falsely reporting exceptions
in pipes.
* minor bug 951: SpiderMonkey scripting objects used to prevent ELinks
from removing files from the memory cache.
* build bug 1044: Check whether -rdynamic works with libraries.

18
src/main/select.c
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@ -10,6 +10,9 @@
#ifdef HAVE_SYS_SIGNAL_H
#include <sys/signal.h>
#endif
#ifdef __GNU__ /* For GNU Hurd bug workaround in set_handlers() */
#include <sys/stat.h> /* OS/2 needs this after sys/types.h */
#endif
#include <sys/types.h>
#ifdef HAVE_SYS_WAIT_H
#include <sys/wait.h>
@ -146,6 +149,21 @@ set_handlers(int fd, select_handler_T read_func, select_handler_T write_func,
fd, FD_SETSIZE);
if_assert_failed return;
#endif
#ifdef __GNU__
/* GNU Hurd pflocal bug <http://savannah.gnu.org/bugs/?22861>:
* If ELinks does a select() where the initial exceptfds set
* includes a pipe that is not listed in the other fd_sets,
* then select() always reports an exception there. That
* makes Elinks think the pipe has failed and close it.
* To work around this bug, do not monitor exceptions for
* pipes on the Hurd. */
if (error_func) {
struct stat st;
if (fstat(fd, &st) == 0 && S_ISFIFO(st.st_mode))
error_func = NULL;
}
#endif /* __GNU__ */
threads[fd].read_func = read_func;
threads[fd].write_func = write_func;
threads[fd].error_func = error_func;