[Xen-devel] [PATCH] xenstore: increase default thread stack size to 32k

[Jim Fehlig <jfehlig@xxxxxxxx>]

On several Skylake machines I've observed xl segfaults when running
create or destroy subcommands. Other subcommands may segfault too,
but I've only looked at create and destroy which share a similar
backtrace

Thread 2 (Thread 0x7ffff7ff3700 (LWP 2941)):
    at /usr/include/bits/unistd.h:44
    at xs.c:398
    fd=<optimized out>) at xs.c:1231

Thread 1 has canceled Thread 2 and is waiting for it in pthread_join().

The backtrace smelled of memory/stack overflow, which was verified by
increasing DEFAULT_THREAD_STACKSIZE to 32kb. Presumably the stack
overflow is observed on Skylake due to a broader CPU feature set which
must be saved within _dl_runtime_resolve and friends.

While PTHREAD_STACK_MIN should advertise a suitable stack size based on
the underlying system, increasing the default size makes xenstore a bit
more robust on systems with insufficient/broken minimums.

Signed-off-by: Jim Fehlig <jfehlig@xxxxxxxx>
---
 tools/xenstore/xs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/xenstore/xs.c b/tools/xenstore/xs.c
index abffd9cd80..3891e4907c 100644
--- a/tools/xenstore/xs.c
+++ b/tools/xenstore/xs.c
@@ -800,7 +800,7 @@ bool xs_watch(struct xs_handle *h, const char *path, const 
char *token)
        struct iovec iov[2];
 
 #ifdef USE_PTHREAD
-#define DEFAULT_THREAD_STACKSIZE (16 * 1024)
+#define DEFAULT_THREAD_STACKSIZE (32 * 1024)
 #define READ_THREAD_STACKSIZE                                  \
        ((DEFAULT_THREAD_STACKSIZE < PTHREAD_STACK_MIN) ?       \
        PTHREAD_STACK_MIN : DEFAULT_THREAD_STACKSIZE)
-- 
2.16.1


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