diff options
| -rw-r--r-- | libbuild2/algorithm.cxx | 2 | ||||
| -rw-r--r-- | libbuild2/context.cxx | 34 | ||||
| -rw-r--r-- | libbuild2/context.hxx | 10 | ||||
| -rw-r--r-- | libbuild2/context.ixx | 2 | ||||
| -rw-r--r-- | libbuild2/scheduler.cxx | 25 | ||||
| -rw-r--r-- | libbuild2/scheduler.hxx | 34 | ||||
| -rw-r--r-- | libbuild2/scheduler.ixx | 14 | ||||
| -rw-r--r-- | libbuild2/scheduler.txx | 38 |
8 files changed, 128 insertions, 31 deletions
diff --git a/libbuild2/algorithm.cxx b/libbuild2/algorithm.cxx index 3d8b89c..62c500d 100644 --- a/libbuild2/algorithm.cxx +++ b/libbuild2/algorithm.cxx @@ -284,7 +284,7 @@ namespace build2 // to switch the phase to load. Which would result in a deadlock // unless we release the phase. // - phase_unlock u (ct.ctx, true /* unlock */, true /* delay */); + phase_unlock u (ct.ctx, true /* delay */); e = ctx.sched->wait (busy - 1, task_count, u, *wq); } diff --git a/libbuild2/context.cxx b/libbuild2/context.cxx index c0442f0..6e4fd6f 100644 --- a/libbuild2/context.cxx +++ b/libbuild2/context.cxx @@ -1124,35 +1124,35 @@ namespace build2 // phase_unlock // phase_unlock:: - phase_unlock (context& c, bool u, bool d) - : ctx (u ? &c : nullptr), lock (nullptr) + phase_unlock (context* c, bool d) + : ctx (c), lock_ (nullptr) { - if (u && !d) + if (ctx != nullptr && !d) unlock (); } void phase_unlock:: unlock () { - if (ctx != nullptr && lock == nullptr) + if (ctx != nullptr && lock_ == nullptr) { - lock = phase_lock_instance; - assert (&lock->ctx == ctx); + lock_ = phase_lock_instance; + assert (&lock_->ctx == ctx); phase_lock_instance = nullptr; // Note: not lock->prev. - ctx->phase_mutex.unlock (lock->phase); + ctx->phase_mutex.unlock (lock_->phase); - //text << this_thread::get_id () << " phase unlock " << lock->phase; + //text << this_thread::get_id () << " phase unlock " << lock_->phase; } } - phase_unlock:: - ~phase_unlock () noexcept (false) + void phase_unlock:: + lock () { - if (lock != nullptr) + if (lock_ != nullptr) { - bool r (ctx->phase_mutex.lock (lock->phase)); - phase_lock_instance = lock; + bool r (ctx->phase_mutex.lock (lock_->phase)); + phase_lock_instance = lock_; // Fail unless we are already failing. Note that we keep the phase // locked since there will be phase_lock down the stack to unlock it. @@ -1160,10 +1160,16 @@ namespace build2 if (!r && !uncaught_exception ()) throw failed (); - //text << this_thread::get_id () << " phase lock " << lock->phase; + //text << this_thread::get_id () << " phase lock " << lock_->phase; } } + phase_unlock:: + ~phase_unlock () noexcept (false) + { + lock (); + } + // phase_switch // phase_switch:: diff --git a/libbuild2/context.hxx b/libbuild2/context.hxx index 2dec54a..33fc892 100644 --- a/libbuild2/context.hxx +++ b/libbuild2/context.hxx @@ -849,14 +849,20 @@ namespace build2 // struct LIBBUILD2_SYMEXPORT phase_unlock { - phase_unlock (context&, bool unlock = true, bool delay = false); + explicit phase_unlock (context*, bool delay = false); + explicit phase_unlock (context& ctx, bool delay = false) + : phase_unlock (&ctx, delay) {} + ~phase_unlock () noexcept (false); void unlock (); + void + lock (); + context* ctx; - phase_lock* lock; + phase_lock* lock_; }; // Assuming we have a lock on the current phase, temporarily switch to a diff --git a/libbuild2/context.ixx b/libbuild2/context.ixx index 7b2a405..6c8c428 100644 --- a/libbuild2/context.ixx +++ b/libbuild2/context.ixx @@ -56,7 +56,7 @@ namespace build2 inline void wait_guard:: wait () { - phase_unlock u (*ctx, phase, true /* delay */); + phase_unlock u (phase ? ctx : nullptr, true /* delay */); ctx->sched->wait (start_count, *task_count, u); task_count = nullptr; } diff --git a/libbuild2/scheduler.cxx b/libbuild2/scheduler.cxx index 5027f90..e3fbcc1 100644 --- a/libbuild2/scheduler.cxx +++ b/libbuild2/scheduler.cxx @@ -93,12 +93,11 @@ namespace build2 } void scheduler:: - deactivate (bool external) + deactivate_impl (bool external, lock&& rl) { - if (max_active_ == 1) // Serial execution. - return; + // Note: assume non-serial execution. - lock l (mutex_); + lock l (move (rl)); // Make sure unlocked on exception. active_--; waiting_++; @@ -131,11 +130,10 @@ namespace build2 } } - void scheduler:: - activate (bool external, bool collision) + scheduler::lock scheduler:: + activate_impl (bool external, bool collision) { - if (max_active_ == 1) // Serial execution. - return; + // Note: assume non-serial execution. lock l (mutex_); @@ -160,6 +158,8 @@ namespace build2 if (shutdown_) throw_generic_error (ECANCELED); + + return l; } void scheduler:: @@ -207,7 +207,10 @@ namespace build2 deallocate (size_t n) { if (max_active_ == 1) // Serial execution. + { + assert (n == 0); return; + } lock l (mutex_); active_ -= n; @@ -216,13 +219,15 @@ namespace build2 size_t scheduler:: suspend (size_t start_count, const atomic_count& task_count) { + assert (max_active_ != 1); // Suspend during serial execution? + wait_slot& s ( wait_queue_[ hash<const atomic_count*> () (&task_count) % wait_queue_size_]); // This thread is no longer active. // - deactivate (false /* external */); + deactivate_impl (false /* external */, lock (mutex_)); // Note that the task count is checked while holding the lock. We also // have to notify while holding the lock (see resume()). The aim here @@ -259,7 +264,7 @@ namespace build2 // This thread is no longer waiting. // - activate (false /* external */, collision); + activate_impl (false /* external */, collision); return tc; } diff --git a/libbuild2/scheduler.hxx b/libbuild2/scheduler.hxx index d3b8ceb..3cc206e 100644 --- a/libbuild2/scheduler.hxx +++ b/libbuild2/scheduler.hxx @@ -192,13 +192,15 @@ namespace build2 // // The external flag indicates whether the wait is for an event external // to the scheduler, that is, triggered by something other than one of the - // threads managed by the scheduler. + // threads managed by the scheduler. This is used to suspend deadlock + // detection (which is progress-based and which cannot be measured for + // external events). // void deactivate (bool external); void - activate (bool external, bool = false); + activate (bool external); // Sleep for the specified duration, deactivating the thread before going // to sleep and re-activating it after waking up (which means this @@ -217,7 +219,7 @@ namespace build2 // Allocate additional active thread count to the current active thread, // for example, to be "passed" to an external program: // - // scheduler::alloc_guard ag (ctx.sched, ctx.sched.max_active () / 2); + // scheduler::alloc_guard ag (*ctx.sched, ctx.sched->max_active () / 2); // args.push_back ("-flto=" + to_string (1 + ag.n)); // run (args); // ag.deallocate (); @@ -242,6 +244,22 @@ namespace build2 void deallocate (size_t); + // Similar to allocate() but reserve all the available threads blocking + // until this becomes possible. Call unlock() on the specified lock before + // deactivating and lock() after activating (can be used to unlock the + // phase). Typical usage: + // + // scheduler::alloc_guard ag (*ctx.sched, + // phase_unlock (ctx, true /* delay */)); + // + // Or, without unlocking the phase: + // + // scheduler::alloc_guard ag (*ctx.sched, phase_unlock (nullptr)); + // + template <typename L> + size_t + serialize (L& lock); + struct alloc_guard { size_t n; @@ -249,6 +267,10 @@ namespace build2 alloc_guard (): n (0), s_ (nullptr) {} alloc_guard (scheduler& s, size_t m): n (s.allocate (m)), s_ (&s) {} + template <typename L, + typename std::enable_if<!std::is_integral<L>::value, int>::type = 0> + alloc_guard (scheduler& s, L&& l): n (s.serialize (l)), s_ (&s) {} + alloc_guard (alloc_guard&& x) noexcept : n (x.n), s_ (x.s_) {x.s_ = nullptr;} @@ -939,6 +961,12 @@ namespace build2 private: optional<size_t> wait_impl (size_t, const atomic_count&, work_queue); + + void + deactivate_impl (bool, lock&&); + + lock + activate_impl (bool, bool); }; } diff --git a/libbuild2/scheduler.ixx b/libbuild2/scheduler.ixx index 96eaee1..f46d035 100644 --- a/libbuild2/scheduler.ixx +++ b/libbuild2/scheduler.ixx @@ -44,6 +44,20 @@ namespace build2 return suspend (start_count, task_count); } + inline void scheduler:: + deactivate (bool external) + { + if (max_active_ != 1) // Serial execution. + deactivate_impl (external, lock (mutex_)); + } + + inline void scheduler:: + activate (bool external) + { + if (max_active_ != 1) // Serial execution. + activate_impl (external, false /* collision */); + } + inline scheduler::queue_mark:: queue_mark (scheduler& s) : tq_ (s.queue ()) diff --git a/libbuild2/scheduler.txx b/libbuild2/scheduler.txx index 460c4d4..87c9384 100644 --- a/libbuild2/scheduler.txx +++ b/libbuild2/scheduler.txx @@ -137,4 +137,42 @@ namespace build2 if (tc.fetch_sub (1, memory_order_release) - 1 <= t.start_count) s.resume (tc); // Resume waiters, if any. } + + template <typename L> + size_t scheduler:: + serialize (L& el) + { + if (max_active_ == 1) // Serial execution. + return 0; + + lock l (mutex_); + + if (active_ == 1) + active_ = max_active_; + else + { + // Wait until we are the only active thread. + // + el.unlock (); + + while (active_ != 1) + { + // While it would have been more efficient to implement this via the + // condition variable notifications, that logic is already twisted + // enough (and took a considerable time to debug). So for now we keep + // it simple and do sleep and re-check. Make the sleep external not to + // trip up the deadlock detection. + // + deactivate_impl (true /* external */, move (l)); + active_sleep (std::chrono::milliseconds (10)); + l = activate_impl (true /* external */, false /* collision */); + } + + active_ = max_active_; + l.unlock (); // Important: unlock before attempting to relock external! + el.lock (); + } + + return max_active_ - 1; + } } |