Changes in uspace/lib/c/generic/fibril_synch.c [63f8966:9414abc] in mainline

File:

• uspace/lib/c/generic/fibril_synch.c (modified) (17 diffs)

uspace/lib/c/generic/fibril_synch.c

@@ -42 +42 @@
 #include <errno.h>
 #include <assert.h>
+#include <stacktrace.h>
+#include <stdlib.h>
 
 static void optimize_execution_power(void)
@@ -56 +58 @@
 }
 
+static void print_deadlock(fibril_owner_info_t *oi)
+{
+        fibril_t *f = (fibril_t *) fibril_get_id();
+
+        printf("Deadlock detected.\n");
+        stacktrace_print();
+
+        printf("Fibril %p waits for primitive %p.\n", f, oi);
+
+        while (oi && oi->owned_by) {
+                printf("Primitive %p is owned by fibril %p.\n",
+                    oi, oi->owned_by);
+                if (oi->owned_by == f)
+                        break;
+                stacktrace_print_fp_pc(context_get_fp(&oi->owned_by->ctx),
+                    oi->owned_by->ctx.pc);
+                printf("Fibril %p waits for primitive %p.\n",
+                     oi->owned_by, oi->owned_by->waits_for);
+                oi = oi->owned_by->waits_for;
+        }
+}
+
+
+static void check_for_deadlock(fibril_owner_info_t *oi)
+{
+        while (oi && oi->owned_by) {
+                if (oi->owned_by == (fibril_t *) fibril_get_id()) {
+                        print_deadlock(oi);
+                        abort();
+                }
+                oi = oi->owned_by->waits_for;
+        }
+}
+
+
 void fibril_mutex_initialize(fibril_mutex_t *fm)
 {
+        fm->oi.owned_by = NULL;
         fm->counter = 1;
         list_initialize(&fm->waiters);
@@ -64 +102 @@
 void fibril_mutex_lock(fibril_mutex_t *fm)
 {
+        fibril_t *f = (fibril_t *) fibril_get_id();
+
         futex_down(&async_futex);
         if (fm->counter-- <= 0) {
@@ -73 +113 @@
                 link_initialize(&wdata.wu_event.link);
                 list_append(&wdata.wu_event.link, &fm->waiters);
+                check_for_deadlock(&fm->oi);
+                f->waits_for = &fm->oi;
                 fibril_switch(FIBRIL_TO_MANAGER);
         } else {
+                fm->oi.owned_by = f;
                 futex_up(&async_futex);
         }
@@ -86 +129 @@
         if (fm->counter > 0) {
                 fm->counter--;
+                fm->oi.owned_by = (fibril_t *) fibril_get_id();
                 locked = true;
         }
@@ -99 +143 @@
                 link_t *tmp;
                 awaiter_t *wdp;
+                fibril_t *f;
         
                 assert(!list_empty(&fm->waiters));
@@ -105 +150 @@
                 wdp->active = true;
                 wdp->wu_event.inlist = false;
+
+                f = (fibril_t *) wdp->fid;
+                fm->oi.owned_by = f;
+                f->waits_for = NULL;
+
                 list_remove(&wdp->wu_event.link);
                 fibril_add_ready(wdp->fid);
                 optimize_execution_power();
+        } else {
+                fm->oi.owned_by = NULL;
         }
 }
@@ -120 +172 @@
 void fibril_rwlock_initialize(fibril_rwlock_t *frw)
 {
+        frw->oi.owned_by = NULL;
         frw->writers = 0;
         frw->readers = 0;
@@ -127 +180 @@
 void fibril_rwlock_read_lock(fibril_rwlock_t *frw)
 {
+        fibril_t *f = (fibril_t *) fibril_get_id();
+        
         futex_down(&async_futex);
         if (frw->writers) {
-                fibril_t *f = (fibril_t *) fibril_get_id();
                 awaiter_t wdata;
 
@@ -138 +192 @@
                 f->flags &= ~FIBRIL_WRITER;
                 list_append(&wdata.wu_event.link, &frw->waiters);
+                check_for_deadlock(&frw->oi);
+                f->waits_for = &frw->oi;
                 fibril_switch(FIBRIL_TO_MANAGER);
         } else {
-                frw->readers++;
+                /* Consider the first reader the owner. */
+                if (frw->readers++ == 0)
+                        frw->oi.owned_by = f;
                 futex_up(&async_futex);
         }
@@ -147 +205 @@
 void fibril_rwlock_write_lock(fibril_rwlock_t *frw)
 {
+        fibril_t *f = (fibril_t *) fibril_get_id();
+        
         futex_down(&async_futex);
         if (frw->writers || frw->readers) {
-                fibril_t *f = (fibril_t *) fibril_get_id();
                 awaiter_t wdata;
 
@@ -158 +217 @@
                 f->flags |= FIBRIL_WRITER;
                 list_append(&wdata.wu_event.link, &frw->waiters);
+                check_for_deadlock(&frw->oi);
+                f->waits_for = &frw->oi;
                 fibril_switch(FIBRIL_TO_MANAGER);
         } else {
+                frw->oi.owned_by = f;
                 frw->writers++;
                 futex_up(&async_futex);
@@ -170 +232 @@
         assert(frw->readers || (frw->writers == 1));
         if (frw->readers) {
-                if (--frw->readers)
+                if (--frw->readers) {
+                        if (frw->oi.owned_by == (fibril_t *) fibril_get_id()) {
+                                /*
+                                 * If this reader firbril was considered the
+                                 * owner of this rwlock, clear the ownership
+                                 * information even if there are still more
+                                 * readers.
+                                 *
+                                 * This is the limitation of the detection
+                                 * mechanism rooted in the fact that tracking
+                                 * all readers would require dynamically
+                                 * allocated memory for keeping linkage info.
+                                 */
+                                frw->oi.owned_by = NULL;
+                        }
                         goto out;
+                }
         } else {
                 frw->writers--;
@@ -177 +254 @@
         
         assert(!frw->readers && !frw->writers);
+        
+        frw->oi.owned_by = NULL;
         
         while (!list_empty(&frw->waiters)) {
@@ -185 +264 @@
                 wdp = list_get_instance(tmp, awaiter_t, wu_event.link);
                 f = (fibril_t *) wdp->fid;
+                
+                f->waits_for = NULL;
                 
                 if (f->flags & FIBRIL_WRITER) {
@@ -194 +275 @@
                         fibril_add_ready(wdp->fid);
                         frw->writers++;
+                        frw->oi.owned_by = f;
                         optimize_execution_power();
                         break;
@@ -201 +283 @@
                         list_remove(&wdp->wu_event.link);
                         fibril_add_ready(wdp->fid);
-                        frw->readers++;
+                        if (frw->readers++ == 0) {
+                                /* Consider the first reader the owner. */
+                                frw->oi.owned_by = f;
+                        }
                         optimize_execution_power();
                 }