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chore add HELIO_STACK_CHECK setting
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this setting ensures healthy stack margins for fibers stacks.

Signed-off-by: Roman Gershman <[email protected]>
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romange committed Dec 19, 2024
1 parent 7fe1f3d commit 7fe12cb
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Showing 4 changed files with 44 additions and 31 deletions.
9 changes: 6 additions & 3 deletions util/fibers/CMakeLists.txt
Original file line number Diff line number Diff line change
Expand Up @@ -14,9 +14,12 @@ add_library(fibers2 fibers.cc proactor_base.cc synchronization.cc
sliding_counter.cc varz.cc fiberqueue_threadpool.cc dns_resolve.cc
${FB_LINUX_SRCS})

option(HELIO_ENABLE_STACK_MEASURE "Enable stack size measuring" OFF)
if (HELIO_ENABLE_STACK_MEASURE)
target_compile_definitions(fibers2 PUBLIC -DCHECK_FIBER_STACK_SIZE_USAGE)
set(HELIO_STACK_CHECK "" CACHE STRING
"Enables fiber stack overflow checks. If set, shoult be a positive integer, that enforces the minimum available margin in bytes.")

if (HELIO_STACK_CHECK)
set_property(SOURCE detail/fiber_interface.cc APPEND PROPERTY COMPILE_DEFINITIONS
CHECK_FIBER_STACK_MARGIN=${HELIO_STACK_CHECK})
endif()

cxx_link(fibers2 base io ${FB_LINUX_LIBS} Boost::context Boost::headers TRDP::cares)
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37 changes: 26 additions & 11 deletions util/fibers/detail/fiber_interface.cc
Original file line number Diff line number Diff line change
Expand Up @@ -157,6 +157,23 @@ ctx::fiber_context FiberInterface::Terminate() {
DCHECK(this == FiberActive());
DCHECK(!list_hook.is_linked());

#ifdef CHECK_FIBER_STACK_MARGIN
{
const uint8_t* ptr = stack_bottom_;
constexpr uint32_t kHardLimit = (CHECK_FIBER_STACK_MARGIN);
while (*ptr == 0xAB) {
++ptr;
}
uint32_t margin = ptr - stack_bottom_;

CHECK_GE(margin, kHardLimit) << "Low stack margin for " << name_;

// Log if margins are within the the orange zone.
LOG_IF(INFO, margin < kHardLimit * 1.5)
<< "Stack margin for " << name_ << ": " << margin << " bytes";
}
#endif

scheduler_->ScheduleTermination(this);
DVLOG(2) << "Terminating " << name_;

Expand All @@ -179,6 +196,14 @@ ctx::fiber_context FiberInterface::Terminate() {
return scheduler_->Preempt();
}

void FiberInterface::InitStackBottom(uint8_t* stack_bottom, uint32_t stack_size) {
stack_bottom_ = stack_bottom;

#ifdef CHECK_FIBER_STACK_MARGIN
memset(stack_bottom_, 0xAB, stack_size);
#endif
}

void FiberInterface::Start(Launch launch) {
auto& fb_init = detail::FbInitializer();
fb_init.sched->Attach(this);
Expand Down Expand Up @@ -307,7 +332,7 @@ void FiberInterface::PullMyselfFromRemoteReadyQueue() {
if (IsScheduledRemotely()) {
LOG(FATAL) << "Failed to pull " << name_ << " from remote_ready_queue. res=" << res
<< " remotenext: " << uint64_t(remote_next_.load(std::memory_order_relaxed))
<< " remotempty: " << scheduler_->RemoteEmpty();
<< " remotempty: " << scheduler_->RemoteEmpty();
}
}

Expand Down Expand Up @@ -384,16 +409,6 @@ void ExecuteOnAllFiberStacks(FiberInterface::PrintFn fn) {
FbInitializer().sched->ExecuteOnAllFiberStacks(std::move(fn));
}


void PrintFiberStackMargin(const void* bottom, const char* name) {
uint8_t* stack_bottom = (uint8_t*)bottom;
uint8_t* ptr = stack_bottom;
while (*ptr == 0xAB) {
++ptr;
}
VLOG(1) << "Stack margin for " << name << ": " << (ptr - stack_bottom) << " bytes";
}

void ActivateSameThread(FiberInterface* active, FiberInterface* other) {
if (active->scheduler() != other->scheduler()) {
LOG(DFATAL) << "Fibers belong to different schedulers";
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26 changes: 9 additions & 17 deletions util/fibers/detail/fiber_interface.h
Original file line number Diff line number Diff line change
Expand Up @@ -59,10 +59,6 @@ using FI_SleepHook =

class Scheduler;

// Enable this define via cmake option
#ifdef CHECK_FIBER_STACK_SIZE_USAGE
void PrintFiberStackMargin(const void* bottom, const char* name);
#endif

class FiberInterface {
friend class Scheduler;
Expand Down Expand Up @@ -220,6 +216,10 @@ class FiberInterface {
#endif
}

uintptr_t stack_bottom() const {
return reinterpret_cast<uintptr_t>(stack_bottom_);
}

protected:
static constexpr uint16_t kTerminatedBit = 0x1;
static constexpr uint16_t kBusyBit = 0x2;
Expand All @@ -228,6 +228,7 @@ class FiberInterface {
static constexpr uint16_t kScheduleRemote = 0x4;

::boost::context::fiber_context Terminate();
void InitStackBottom(uint8_t* stack_bottom, uint32_t stack_size);

std::atomic<uint32_t> use_count_; // used for intrusive_ptr refcounting.

Expand Down Expand Up @@ -256,10 +257,12 @@ class FiberInterface {
uint64_t cpu_tsc_ = 0;
char name_[24];
uint32_t stack_size_ = 0;
uint8_t* stack_bottom_ = nullptr;
private:
#ifndef NDEBUG
std::function<std::string()> stacktrace_print_cb_;
#endif

// Handles all the stats and also updates the involved data structure before actually switching
// the fiber context. Returns the active fiber before the context switch.
FiberInterface* SwitchSetup();
Expand All @@ -275,11 +278,7 @@ template <typename Fn, typename... Arg> class WorkerFiberImpl : public FiberInte
: FiberInterface(WORKER, 1, name), fn_(std::forward<Fn>(fn)),
arg_(std::forward<Arg>(arg)...) {
stack_size_ = palloc.sctx.size; // The whole stack size that was allocated for this fiber.

#ifdef CHECK_FIBER_STACK_SIZE_USAGE
stack_bottom_ = reinterpret_cast<uint8_t*>(palloc.sp) - palloc.size;
memset(stack_bottom_, 0xAB, palloc.size);
#endif
InitStackBottom(reinterpret_cast<uint8_t*>(palloc.sp) - palloc.size, palloc.size);

entry_ = FbCntx(std::allocator_arg, palloc, std::forward<StackAlloc>(salloc),
[this](FbCntx&& caller) { return run_(std::move(caller)); });
Expand All @@ -300,22 +299,15 @@ template <typename Fn, typename... Arg> class WorkerFiberImpl : public FiberInte
#if defined(BOOST_USE_UCONTEXT)
std::move(c).resume();
#endif

std::apply(std::move(fn), std::move(arg));
}
#ifdef CHECK_FIBER_STACK_SIZE_USAGE
PrintFiberStackMargin(stack_bottom_, name_);
#endif

return Terminate();
}

// Without decay - fn_ can be a reference, depending how a function is passed to the constructor.
typename std::decay<Fn>::type fn_;
std::tuple<std::decay_t<Arg>...> arg_;

#ifdef CHECK_FIBER_STACK_SIZE_USAGE
void* stack_bottom_;
#endif
};

template <typename FbImpl>
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3 changes: 3 additions & 0 deletions util/fibers/fibers_test.cc
Original file line number Diff line number Diff line change
Expand Up @@ -747,6 +747,8 @@ TEST_P(ProactorTest, NotifyRemote) {
fb2.Join();
}

// Disable EXPECT_DEATH because it messes up with info logs.
#if 0
TEST_P(ProactorTest, BriefDontBlock) {
Done done;

Expand All @@ -756,6 +758,7 @@ TEST_P(ProactorTest, BriefDontBlock) {
#endif
});
}
#endif

TEST_P(ProactorTest, Timeout) {
EventCount ec;
Expand Down

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