The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_tslog.c

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    1 /*-
    2  * Copyright (c) 2017 Colin Percival
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  *
   14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   24  * SUCH DAMAGE.
   25  */
   26 
   27 #include <sys/cdefs.h>
   28 __FBSDID("$FreeBSD: releng/12.0/sys/kern/kern_tslog.c 327423 2017-12-31 09:21:01Z cperciva $");
   29 
   30 #include <sys/param.h>
   31 #include <sys/sbuf.h>
   32 #include <sys/sysctl.h>
   33 #include <sys/systm.h>
   34 #include <sys/tslog.h>
   35 
   36 #include <machine/atomic.h>
   37 #include <machine/cpu.h>
   38 
   39 #ifndef TSLOGSIZE
   40 #define TSLOGSIZE 262144
   41 #endif
   42 
   43 static volatile long nrecs = 0;
   44 static struct timestamp {
   45         void * td;
   46         int type;
   47         const char * f;
   48         const char * s;
   49         uint64_t tsc;
   50 } timestamps[TSLOGSIZE];
   51 
   52 void
   53 tslog(void * td, int type, const char * f, const char * s)
   54 {
   55         uint64_t tsc = get_cyclecount();
   56         long pos;
   57 
   58         /* Grab a slot. */
   59         pos = atomic_fetchadd_long(&nrecs, 1);
   60 
   61         /* Store record. */
   62         if (pos < nitems(timestamps)) {
   63                 timestamps[pos].td = td;
   64                 timestamps[pos].type = type;
   65                 timestamps[pos].f = f;
   66                 timestamps[pos].s = s;
   67                 timestamps[pos].tsc = tsc;
   68         }
   69 }
   70 
   71 static int
   72 sysctl_debug_tslog(SYSCTL_HANDLER_ARGS)
   73 {
   74         int error;
   75         struct sbuf *sb;
   76         size_t i, limit;
   77 
   78         /*
   79          * This code can race against the code in tslog() which stores
   80          * records: Theoretically we could end up reading a record after
   81          * its slots have been reserved but before it has been written.
   82          * Since this code takes orders of magnitude longer to run than
   83          * tslog() takes to write a record, it is highly unlikely that
   84          * anyone will ever experience this race.
   85          */
   86         sb = sbuf_new_for_sysctl(NULL, NULL, 1024, req);
   87         limit = MIN(nrecs, nitems(timestamps));
   88         for (i = 0; i < limit; i++) {
   89                 sbuf_printf(sb, "%p", timestamps[i].td);
   90                 sbuf_printf(sb, " %llu",
   91                     (unsigned long long)timestamps[i].tsc);
   92                 switch (timestamps[i].type) {
   93                 case TS_ENTER:
   94                         sbuf_printf(sb, " ENTER");
   95                         break;
   96                 case TS_EXIT:
   97                         sbuf_printf(sb, " EXIT");
   98                         break;
   99                 case TS_THREAD:
  100                         sbuf_printf(sb, " THREAD");
  101                         break;
  102                 case TS_EVENT:
  103                         sbuf_printf(sb, " EVENT");
  104                         break;
  105                 }
  106                 sbuf_printf(sb, " %s", timestamps[i].f ? timestamps[i].f : "(null)");
  107                 if (timestamps[i].s)
  108                         sbuf_printf(sb, " %s\n", timestamps[i].s);
  109                 else
  110                         sbuf_printf(sb, "\n");
  111         }
  112         error = sbuf_finish(sb);
  113         sbuf_delete(sb);
  114         return (error);
  115 }
  116 
  117 SYSCTL_PROC(_debug, OID_AUTO, tslog, CTLTYPE_STRING|CTLFLAG_RD|CTLFLAG_MPSAFE,
  118     0, 0, sysctl_debug_tslog, "", "Dump recorded event timestamps");

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