On 03/02/2018 05:40 AM, Wei Liu wrote:
On Fri, Mar 02, 2018 at 12:29:31PM +0000, Wei Liu wrote:
On Mon, Feb 26, 2018 at 09:53:38AM -0700, Jim Fehlig wrote:
On 02/26/2018 01:46 AM, Juergen Gross wrote:
When creating a pthread in xs_watch() try to get the minimal needed
size of the thread from glibc instead of using a constant. This avoids
problems when the library is used in programs with large per-thread

Use dlsym() to get the pointer to __pthread_get_minstack() in order to
avoid linkage problems and fall back to the current constant size if
not found.

Signed-off-by: Juergen Gross <jgr...@suse.com>
- use _GNU_SOURCE (Wei Liu)
- call __pthread_get_minstack() with parameter
- add -ldl to correct make flags
- ensure to not using smaller stack size than today
   tools/xenstore/Makefile |  4 ++++
   tools/xenstore/xs.c     | 21 ++++++++++++++++++++-
   2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/tools/xenstore/Makefile b/tools/xenstore/Makefile
index 2b99d2bc1b..0831be0b6f 100644
--- a/tools/xenstore/Makefile
+++ b/tools/xenstore/Makefile
@@ -100,6 +100,10 @@ libxenstore.so.$(MAJOR): libxenstore.so.$(MAJOR).$(MINOR)
        ln -sf $< $@
   xs.opic: CFLAGS += -DUSE_PTHREAD
+ifeq ($(CONFIG_Linux),y)
+xs.opic: CFLAGS += -DUSE_DLSYM
+libxenstore.so.$(MAJOR).$(MINOR): LDFLAGS += -ldl

Dropping this patch in one of my automated builds caused a libxenstore link 

[   99s] gcc    -lsystemd -ldl -pthread -Wl,-soname -Wl,libxenstore.so.3.0
-shared -o libxenstore.so.3.0.3 xs.opic xs_lib.opic 

[   99s] 
undefined reference to `dlsym'

I hacked around it by appending '-ldl' to the end of the subsequent
libxenstore.so rule.

Hmm... Maybe I'm a bit dense today. I know the position of -l matters
but I don't quite understand how placing -pthread before xs.opic works
but -ldl doesn't. xs.c uses both after all.

I'm indeed very dense -- -pthread is a special option that sets the
proper flags for linking pthread library for both the preprocessor and

But still, Juergen must have tested the change, so I wonder why it
doesn't work in your setup. What is your build environment? Gcc version?

I dropped the patch in a package build on the openSUSE build service, where gcc7 was used. But I don't see the problem when building from sources with gcc7. Apparently we have a bug in our package build, so ignore this comment. Tested-by still stands though :-).


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