lazy stack: activate lazy stack in pthreads

This patch adds new mmap flag - mmap_stack - that is used when mmaping
a stack when creating new pthread. This new flag is only used when
the build parameter CONF_lazy_stack is enabled.

Signed-off-by: Waldemar Kozaczuk <[email protected]>

Author: wkozaczuk

include/osv/mmu-defs.hh

@@ -84,6 +84,7 @@ enum {
     mmap_small       = 1ul << 5,
     mmap_jvm_balloon = 1ul << 6,
     mmap_file        = 1ul << 7,
+    mmap_stack       = 1ul << 8,
 };
 
 enum {

libc/mman.cc

@@ -43,12 +43,7 @@ unsigned libc_flags_to_mmap(int flags)
         mmap_flags |= mmu::mmap_populate;
     }
     if (flags & MAP_STACK) {
-        // OSv currently requires that stacks be pinned (see issue #143). So
-        // if an application wants to mmap() a stack for pthread_attr_setstack
-        // and did us the courtesy of telling this to ue (via MAP_STACK),
-        // let's return the courtesy by returning pre-faulted memory.
-        // FIXME: If issue #143 is fixed, this workaround should be removed.
-        mmap_flags |= mmu::mmap_populate;
+        mmap_flags |= mmu::mmap_stack;
     }
     if (flags & MAP_SHARED) {
         mmap_flags |= mmu::mmap_shared;

libc/pthread.cc

@@ -141,7 +141,12 @@ namespace pthread_private {
             return {attr.stack_begin, attr.stack_size};
         }
         size_t size = attr.stack_size;
-        void *addr = mmu::map_anon(nullptr, size, mmu::mmap_populate, mmu::perm_rw);
+#if CONF_lazy_stack
+        unsigned stack_flags = mmu::mmap_stack;
+#else
+        unsigned stack_flags = mmu::mmap_populate;
+#endif
+        void *addr = mmu::map_anon(nullptr, size, stack_flags, mmu::perm_rw);
         mmu::mprotect(addr, attr.guard_size, 0);
         sched::thread::stack_info si{addr, size};
         si.deleter = free_stack;