uClibc daemon/pthred fix (need on 0.9.29 and 0.9.30)

[Luigi 'Comio' Mantellini <luigi.mantellini@…>]

Dear,

the last uclibc has a broken "daemon" function implementation. "daemon" calls a wrong "fork" function (libc instead linuxthreads version) breaking the pthread environment.

This trivial patch permits a correct linking with the pthread "fork" implementation making the daemon call usable also with the last uClibc.

Best regards,

luigi

[luigi.mantellini@…]

This patch covers changes like: ​/changeset/13712.html and many other.

Let me say that the final solution is to switch to nptl (when it will be available... mena carmelo!)

ciao

luigi

[olistudent]

Are you sure that your patch fixes the problem. I tested with the simple test case from ​https://bugs.busybox.net/show_bug.cgi?id=193. But it still hangs.
Nevertheless your assumption seems to be correct that the wrong fork function is used. I replaced fork in daemon.c with fork and then it works for me.

I'm not using the OpenWRT toolchain. Perhaps this is the reason why your patch doesn't work for me?

[olistudent]

Sorry, didn't use the preview function. I replaced fork() with __fork().

[olistudent]

libc/unistd/daemon.c

@@ -54 +54 @@
 libc_hidden_proto(dup2)
 libc_hidden_proto(setsid)
 libc_hidden_proto(chdir)
-libc_hidden_proto(fork)
 
 int daemon( int nochdir, int noclose )
 {
        int fd;
 
-       switch (fork()) {
+       switch (__fork()) {
                case -1:
                        return(-1);
                case 0:
@@ -74 +73 @@
 
        /* Make certain we are not a session leader, or else we
         * might reacquire a controlling terminal */
-       if (fork())
+       if (__fork())
                _exit(0);
 
        if (!nochdir)

[luigi.mantellini@…]

Replying to olistudent:

Are you sure that your patch fixes the problem. I tested with the simple test case from ​https://bugs.busybox.net/show_bug.cgi?id=193. But it still hangs.

The real problem is that the pthread implementation is really ugly. I'm waiting for the last nptl implementation.

Nevertheless your assumption seems to be correct that the wrong fork function is used. I replaced fork in daemon.c with fork and then it works for me.

I debugged using the jtag interface and I checked the complete execution flow... discovering the issue.

I'm not using the OpenWRT toolchain. Perhaps this is the reason why your patch doesn't work for me?

may be.

[anonymous]

I think that this is not a solution, because the pthread support is optional and you need to use a weak linking.

luigi

Replying to olistudent:

...

+ switch (fork()) {

...

}}}

[olistudent]

Wondering why here is no reference to #4915...

I did further research on this topic and recognized that your patch fixes this problem for dynamic linked libpthread but not for static version. Can you confirm this?

[Luigi 'Comio' Mantellini <luigi.mantellini@…>]

I'm using only dynamic libs. I'm sorry I cannot confirm.

A better solution may be to choose the correct fork implementation by means of #ifdef/#else/#endef construct.

best regards,

luigi

[nbd]

fix added in r15344, static library issue still pending.
i don't think #ifdef would work, since the same daemon() implementation would be used for both pthread and non-pthread variants, thus can't really be separated.
no idea what a real solution would look like, though.

[mcy@…]

Hello,

The problem is still present in OpenWrt 10.03.1 for static linking. Is there any progress here? If you need me to do some tests, I would be happy to help.

Cheers,

Matteo

[jow]

Try trunk with ntpl, we're not going to fix this for backfire. If you find this to be still an issue open a separate ticket.

[jow]

Milestone Attitude Adjustment 12.09 deleted