Changeset 926d358 for libcfa/src

Timestamp:

Oct 11, 2022, 4:50:36 PM (2 years ago)

Author:

Thierry Delisle <tdelisle@…>

Branches:

ADT, ast-experimental, master

Children:

e5256bd

Parents:

3fcb5921

Message:

Removed old asm_labels.
Modified preemption check to no longer poll interrupts.
Modified poll_interrupts to be lighter weight and remove redundant checks/safeties.

File:

• libcfa/src/concurrency/preemption.cfa (modified) (4 diffs)

libcfa/src/concurrency/preemption.cfa

@@ -232 +232 @@
 // available.
 
-//-----------------------------------------------------------------------------
-// Some assembly required
-#define __cfaasm_label(label, when) when: asm volatile goto(".global __cfaasm_" #label "_" #when "\n" "__cfaasm_" #label "_" #when ":":::"memory":when)
-
 //----------
 // special case for preemption since used often
-__attribute__((optimize("no-reorder-blocks"))) bool __preemption_enabled() libcfa_nopreempt libcfa_public {
-        // create a assembler label before
-        // marked as clobber all to avoid movement
-        __cfaasm_label(check, before);
-
+bool __preemption_enabled() libcfa_nopreempt libcfa_public {
         // access tls as normal
-        bool enabled = __cfaabi_tls.preemption_state.enabled;
-
-        // Check if there is a pending preemption
-        processor   * proc = __cfaabi_tls.this_processor;
-        bool pending = proc ? proc->pending_preemption : false;
-        if( enabled && pending ) proc->pending_preemption = false;
-
-        // create a assembler label after
-        // marked as clobber all to avoid movement
-        __cfaasm_label(check, after);
-
-        // If we can preempt and there is a pending one
-        // this is a good time to yield
-        if( enabled && pending ) {
-                force_yield( __POLL_PREEMPTION );
-        }
-        return enabled;
-}
-
-struct asm_region {
-        void * before;
-        void * after;
-};
-
-static inline bool __cfaasm_in( void * ip, struct asm_region & region ) {
-        return ip >= region.before && ip <= region.after;
+        return __cfaabi_tls.preemption_state.enabled;
 }
 
@@ -293 +260 @@
 uintptr_t __cfatls_get( unsigned long int offset ) libcfa_nopreempt libcfa_public; //no inline to avoid problems
 uintptr_t __cfatls_get( unsigned long int offset ) {
-        // create a assembler label before
-        // marked as clobber all to avoid movement
-        __cfaasm_label(get, before);
-
         // access tls as normal (except for pointer arithmetic)
         uintptr_t val = *(uintptr_t*)((uintptr_t)&__cfaabi_tls + offset);
 
-        // create a assembler label after
-        // marked as clobber all to avoid movement
-        __cfaasm_label(get, after);
-
         // This is used everywhere, to avoid cost, we DO NOT poll pending preemption
         return val;
@@ -310 +269 @@
 extern "C" {
         // Disable interrupts by incrementing the counter
-        void disable_interrupts() libcfa_nopreempt libcfa_public {
-                // create a assembler label before
-                // marked as clobber all to avoid movement
-                __cfaasm_label(dsable, before);
-
-                with( __cfaabi_tls.preemption_state ) {
-                        #if GCC_VERSION > 50000
-                        static_assert(__atomic_always_lock_free(sizeof(enabled), &enabled), "Must be lock-free");
-                        #endif
-
-                        // Set enabled flag to false
-                        // should be atomic to avoid preemption in the middle of the operation.
-                        // use memory order RELAXED since there is no inter-thread on this variable requirements
-                        __atomic_store_n(&enabled, false, __ATOMIC_RELAXED);
-
-                        // Signal the compiler that a fence is needed but only for signal handlers
-                        __atomic_signal_fence(__ATOMIC_ACQUIRE);
-
-                        __attribute__((unused)) unsigned short new_val = disable_count + 1;
-                        disable_count = new_val;
-                        verify( new_val < 65_000u );              // If this triggers someone is disabling interrupts without enabling them
-                }
-
-                // create a assembler label after
-                // marked as clobber all to avoid movement
-                __cfaasm_label(dsable, after);
-
+        void disable_interrupts() libcfa_nopreempt libcfa_public with( __cfaabi_tls.preemption_state ) {
+                #if GCC_VERSION > 50000
+                static_assert(__atomic_always_lock_free(sizeof(enabled), &enabled), "Must be lock-free");
+                #endif
+
+                // Set enabled flag to false
+                // should be atomic to avoid preemption in the middle of the operation.
+                // use memory order RELAXED since there is no inter-thread on this variable requirements
+                __atomic_store_n(&enabled, false, __ATOMIC_RELAXED);
+
+                // Signal the compiler that a fence is needed but only for signal handlers
+                __atomic_signal_fence(__ATOMIC_ACQUIRE);
+
+                __attribute__((unused)) unsigned short new_val = disable_count + 1;
+                disable_count = new_val;
+                verify( new_val < 65_000u );              // If this triggers someone is disabling interrupts without enabling them
         }
 
@@ -379 +327 @@
         // i.e. on a real processor and not in the kernel
         // (can return true even if no preemption was pending)
-        bool poll_interrupts() libcfa_public {
+        bool poll_interrupts() libcfa_nopreempt libcfa_public {
                 // Cache the processor now since interrupts can start happening after the atomic store
-                processor   * proc = publicTLS_get( this_processor );
+                processor   * proc =  __cfaabi_tls.this_processor;
                 if ( ! proc ) return false;
-                if ( ! __preemption_enabled() ) return false;
-
-                with( __cfaabi_tls.preemption_state ){
-                        // Signal the compiler that a fence is needed but only for signal handlers
-                        __atomic_signal_fence(__ATOMIC_RELEASE);
-                        if( proc->pending_preemption ) {
-                                proc->pending_preemption = false;
-                                force_yield( __POLL_PREEMPTION );
-                        }
+                if ( ! __cfaabi_tls.preemption_state.enabled ) return false;
+
+                // Signal the compiler that a fence is needed but only for signal handlers
+                __atomic_signal_fence(__ATOMIC_RELEASE);
+                if( unlikely( proc->pending_preemption ) ) {
+                        proc->pending_preemption = false;
+                        force_yield( __POLL_PREEMPTION );
                 }