Increase the stack space in userspace.

[zfs.git] / lib / libzpool / kernel.c

diff --git a/lib/libzpool/kernel.c b/lib/libzpool/kernel.c
index 69fbd44..704f3d6 100644 (file)
--- a/lib/libzpool/kernel.c
+++ b/lib/libzpool/kernel.c
@@ -159,9 +159,14 @@ zk_thread_create(caddr_t stk, size_t stksize, thread_func_t func, void *arg,
         *
         * We reduce the default stack size in userspace, to ensure
         * we observe stack overruns in user space as well as in
-        * kernel space.  PTHREAD_STACK_MIN is the minimum stack
-        * required for a NULL procedure in user space and is added
-        * in to the stack requirements.
+        * kernel space. In practice we can't set the userspace stack
+        * size to 8k because differences in stack usage between kernel
+        * space and userspace could lead to spurious stack overflows
+        * (especially when debugging is enabled). Nevertheless, we try
+        * to set it to the lowest value that works (currently 8k*4).
+        * PTHREAD_STACK_MIN is the minimum stack required for a NULL
+        * procedure in user space and is added in to the stack
+        * requirements.
         *
         * Some buggy NPTL threading implementations include the
         * guard area within the stack size allocations.  In
@@ -170,7 +175,7 @@ zk_thread_create(caddr_t stk, size_t stksize, thread_func_t func, void *arg,
         * on Linux.
         */
 
-       stack = PTHREAD_STACK_MIN + MAX(stksize, STACK_SIZE) +
+       stack = PTHREAD_STACK_MIN + MAX(stksize, STACK_SIZE) * 4 +
                        EXTRA_GUARD_BYTES;
 
        VERIFY3S(pthread_attr_init(&attr), ==, 0);