1 /* Copyright (c) 2009-2020. The SimGrid Team. All rights reserved. */
3 /* This program is free software; you can redistribute it and/or modify it
4 * under the terms of the license (GNU LGPL) which comes with this package. */
6 /* \file UContext.cpp Context switching with ucontexts from System V */
9 #include "simgrid/Exception.hpp"
10 #include "src/kernel/actor/ActorImpl.hpp"
11 #include "src/mc/mc_ignore.hpp"
12 #include "src/simix/smx_private.hpp"
14 #include "ContextUnix.hpp"
16 XBT_LOG_EXTERNAL_DEFAULT_CATEGORY(simix_context);
18 /** Up to two integers may be needed to store a pointer on the system we target */
19 constexpr int CTX_ADDR_LEN = 2;
21 static_assert(sizeof(simgrid::kernel::context::UContext*) <= CTX_ADDR_LEN * sizeof(int),
22 "Ucontexts are not supported on this arch yet. Please increase CTX_ADDR_LEN.");
24 // This function is called by makecontext(3): use extern "C" to have C language linkage for its type
26 XBT_ATTRIB_NORETURN static void sysv_ctx_wrapper(int i1, int i2)
28 // Rebuild the Context* pointer from the integers:
29 int ctx_addr[CTX_ADDR_LEN] = {i1, i2};
30 simgrid::kernel::context::UContext* context;
31 memcpy(&context, ctx_addr, sizeof context);
32 smx_ctx_wrapper(context);
41 UContext* UContextFactory::create_context(std::function<void()>&& code, actor::ActorImpl* actor)
43 return new_context<UContext>(std::move(code), actor, this);
49 UContext::UContext(std::function<void()>&& code, actor::ActorImpl* actor, SwappedContextFactory* factory)
50 : SwappedContext(std::move(code), actor, factory)
52 XBT_VERB("Creating a context of stack %uMb", actor->get_stacksize() / 1024 / 1024);
53 /* if the user provided a function for the actor then use it. If not, nothing to do for maestro. */
55 getcontext(&this->uc_);
56 this->uc_.uc_link = nullptr;
57 this->uc_.uc_stack.ss_sp = sg_makecontext_stack_addr(get_stack());
58 this->uc_.uc_stack.ss_size = sg_makecontext_stack_size(actor->get_stacksize());
59 // Makecontext expects integer arguments; we want to pass a pointer.
60 // This context address is decomposed into a series of integers, which are passed as arguments to makecontext.
62 int ctx_addr[CTX_ADDR_LEN]{};
64 memcpy(ctx_addr, &arg, sizeof this);
65 makecontext(&this->uc_, (void (*)())sysv_ctx_wrapper, 2, ctx_addr[0], ctx_addr[1]);
69 MC_register_stack_area(get_stack(), &(this->uc_), smx_context_stack_size);
75 void UContext::swap_into_for_real(SwappedContext* to_)
77 const UContext* to = static_cast<UContext*>(to_);
78 swapcontext(&this->uc_, &to->uc_);
82 XBT_PRIVATE ContextFactory* sysv_factory()
84 XBT_VERB("Activating SYSV context factory");
85 return new UContextFactory();
87 } // namespace context
89 } // namespace simgrid