update usertrace fast

[lttv.git] / ltt-usertrace / ltt / ltt-usertrace-fast.h

diff --git a/ltt-usertrace/ltt/ltt-usertrace-fast.h b/ltt-usertrace/ltt/ltt-usertrace-fast.h
index b90a100629b43d221f156cb1ef061a1eaeaaad23..fb01893684259d7ab09bbab69610e792f25ed22b 100644 (file)
--- a/ltt-usertrace/ltt/ltt-usertrace-fast.h
+++ b/ltt-usertrace/ltt/ltt-usertrace-fast.h
@@ -53,7 +53,7 @@ extern "C" {
 
 #define LTT_TRACER_MAGIC_NUMBER                 0x00D6B7ED
 #define LTT_TRACER_VERSION_MAJOR               0
-#define LTT_TRACER_VERSION_MINOR               7
+#define LTT_TRACER_VERSION_MINOR               8
 
 #ifndef atomic_cmpxchg
 #define atomic_cmpxchg(v, old, new) ((int)cmpxchg(&((v)->counter), old, new))
@@ -71,12 +71,14 @@ struct ltt_trace_header {
        uint8_t                                 flight_recorder;
        uint8_t                                 has_heartbeat;
        uint8_t                                 has_alignment;  /* Event header alignment */
+       uint8_t                                 tsc_lsb_truncate;
+       uint8_t                                 tscbits;
        uint32_t                                freq_scale;
        uint64_t                                start_freq;
        uint64_t                                start_tsc;
        uint64_t                                start_monotonic;
-  uint64_t        start_time_sec;
-  uint64_t        start_time_usec;
+       uint64_t                                start_time_sec;
+       uint64_t                                start_time_usec;
 } __attribute((packed));
 
 
@@ -366,6 +368,7 @@ static inline void * __attribute__((no_instrument_function)) ltt_reserve_slot(
        int consumed_old, consumed_new;
        int commit_count, reserve_count;
        int ret;
+       sigset_t oldset, set;
 
        do {
                offset_old = atomic_read(&ltt_buf->offset);
@@ -406,29 +409,40 @@ static inline void * __attribute__((no_instrument_function)) ltt_reserve_slot(
                                                                                                                                                                                                                                 ltt_buf)])
                                - atomic_read(&ltt_buf->commit_count[SUBBUF_INDEX(offset_begin,
                                                                                                                                                                                 ltt_buf)]);
+
                        if(reserve_commit_diff == 0) {
                                /* Next buffer not corrupted. */
                                //if((SUBBUF_TRUNC(offset_begin, ltt_buf) 
                                //                              - SUBBUF_TRUNC(atomic_read(&ltt_buf->consumed), ltt_buf))
                                //                                      >= ltt_buf->alloc_size) {
-                               /* sem_wait is not signal safe. Disable signals around it. */
                                {
-                                       sigset_t oldset, set;
-
+                                       /* sem_wait is not signal safe. Disable signals around it.
+                                        * Signals are kept disabled to make sure we win the cmpxchg. */
                                        /* Disable signals */
                                        ret = sigfillset(&set);
                                        if(ret) perror("LTT Error in sigfillset\n"); 
-                                       
+       
                                        ret = pthread_sigmask(SIG_BLOCK, &set, &oldset);
                                        if(ret) perror("LTT Error in pthread_sigmask\n");
 
+                                       /* We detect if a signal came between
+                                        * the offset read and signal disabling:
+                                        * if it is the case, then we restart
+                                        * the loop after reenabling signals. It
+                                        * means that it's a signal that has
+                                        * won the buffer switch.*/
+                                       if(offset_old != atomic_read(&ltt_buf->offset)) {
+                                               ret = pthread_sigmask(SIG_SETMASK, &oldset, NULL);
+                                               if(ret) perror("LTT Error in pthread_sigmask\n");
+                                               continue;
+                                       }
+                                       /* If the offset is still the same, then
+                                        * we can safely proceed to do the
+                                        * buffer switch without being
+                                        * interrupted by a signal. */
                                        sem_wait(&ltt_buf->writer_sem);
 
-                                       /* Enable signals */
-                                       ret = pthread_sigmask(SIG_SETMASK, &oldset, NULL);
-                                       if(ret) perror("LTT Error in pthread_sigmask\n");
                                }
-
                                        /* go on with the write */
 
                                //} else {
@@ -438,7 +452,8 @@ static inline void * __attribute__((no_instrument_function)) ltt_reserve_slot(
                        } else {
                                /* Next subbuffer corrupted. Force pushing reader even in normal
                                 * mode. It's safe to write in this new subbuffer. */
-                               sem_post(&ltt_buf->writer_sem);
+                               /* No sem_post is required because we fall through without doing a
+                                * sem_wait. */
                        }
                        size = ltt_get_header_size(trace, ltt_buf->start + offset_begin,
                                        before_hdr_pad, after_hdr_pad, header_size) + data_size;
@@ -446,6 +461,10 @@ static inline void * __attribute__((no_instrument_function)) ltt_reserve_slot(
                                /* Event too big for subbuffers, report error, don't complete 
                                 * the sub-buffer switch. */
                                atomic_inc(&ltt_buf->events_lost);
+                               if(reserve_commit_diff == 0) {
+                                       ret = pthread_sigmask(SIG_SETMASK, &oldset, NULL);
+                                       if(ret) perror("LTT Error in pthread_sigmask\n");
+                               }
                                return NULL;
                        } else {
                                /* We just made a successful buffer switch and the event fits in the
@@ -466,7 +485,6 @@ static inline void * __attribute__((no_instrument_function)) ltt_reserve_slot(
        } while(atomic_cmpxchg(&ltt_buf->offset, offset_old, offset_end)
                                                        != offset_old);
 
-
        /* Push the reader if necessary */
        do {
                consumed_old = atomic_read(&ltt_buf->consumed);
@@ -541,6 +559,14 @@ static inline void * __attribute__((no_instrument_function)) ltt_reserve_slot(
        }
 
        if(begin_switch) {
+               /* Enable signals : this is what guaranteed that same reserve which did the
+                * sem_wait does in fact win the cmpxchg for the offset. We only call
+                * these system calls on buffer boundaries because of their performance
+                * cost. */
+               if(reserve_commit_diff == 0) {
+                       ret = pthread_sigmask(SIG_SETMASK, &oldset, NULL);
+                       if(ret) perror("LTT Error in pthread_sigmask\n");
+               }
                /* New sub-buffer */
                /* This code can be executed unordered : writers may already have written
                         to the sub-buffer before this code gets executed, caution. */