Fix usleep() bug causing excessive host CPU consumption:

The root cause of the bug was in my incorrect #define of MAX_TOD_UPDATE_USECS in featall.h, which was #defined to 1000000 (one million) instead of 999999, thereby causing the TXF rubato_thread to do a usleep for 1000000 (one million) microseconds, which, being invalid, was causing it to not sleep at all and instead return immediately with an error, causing it to loop continuously without sleeping, consuming all available host CPU due to the timer threads being the highest priority thread in Hercules.

comm3705.c also had a similar bug wherein it was using "min(1000000,delay)" for one of its usleep().

In addition to fixing the previously mentioned bug, I have also introduced a new USLEEP() macro which calls a new "herc_usleep()" function that will report any usleep() error that might occur. (I purposely did not code it to fix (hide) the problem but rather to just report it so that the caller can thus be fixed to not make invalid usleep calls.)

This should close GitHub Issue #589 "Auxiliary threads eating up CPU time" as well as the long running "CPU utilization on Raspberry Pi" thread that took place in the main Hercules group recently.

cckddasd.c

@@ -310,7 +310,7 @@ int             rc, i;                  /* Return code, Loop index   */
     while (cckd->ras)
     {
         release_lock(&cckdblk.ralock);
-        usleep(1);
+        USLEEP(1);
         obtain_lock(&cckdblk.ralock);
     }
     release_lock(&cckdblk.ralock);

cckddasd64.c

@@ -140,7 +140,7 @@ int             rc, i;                  /* Return code, Loop index   */
     while (cckd->ras)
     {
         release_lock(&cckdblk.ralock);
-        usleep(1);
+        USLEEP(1);
         obtain_lock(&cckdblk.ralock);
     }
     release_lock(&cckdblk.ralock);

cgibin.c

@@ -280,7 +280,7 @@ int     msgcount = 22;
         panel_command(command);
         // Wait a bit before proceeding in case
         // the command issues a lot of messages
-        usleep(50000);
+        USLEEP(50000);
     }
 
     if((value = cgi_variable(webblk,"msgcount")))
@@ -1623,7 +1623,7 @@ void cgibin_api_v1_syslog(WEBBLK *webblk)
         panel_command(command);
         // Wait a bit before proceeding in case
         // the command issues a lot of messages
-        usleep(50000);
+        USLEEP(50000);
         hprintf(webblk->sock,"{\"command\": \"%s\",",command);
     } 
     else

channel.c

@@ -338,7 +338,7 @@ typedef struct PREFETCH PREFETCH;
 #define IODELAY(_dev) \
 do { \
   if (sysblk.iodelay > 0 && (_dev)->devchar[10] == 0x20) \
-    usleep(sysblk.iodelay); \
+    USLEEP(sysblk.iodelay); \
 } while(0)
 #else
 #define IODELAY(_dev)
@@ -4151,7 +4151,7 @@ do {                                                                   \
 #ifdef FEATURE_S370_CHANNEL
             if (dev->devtype == 0x2703)
                 if (dev->commadpt->lnctl == COMMADPT_LNCTL_ASYNC)
-                    usleep(5000);
+                    USLEEP(5000);
 #endif
 
 #if DEBUG_DUMP

cmdtab.h

@@ -1828,7 +1828,8 @@
   "When the z/Arch Transactional-Execution Facility *is* installed and\n"       \
   "enabled the minimum and default intervals are 200 and 400 microseconds.\n"   \
   "\n"                                                                          \
-  "The maximum allowed interval is 1000000 microseconds (one second).\n"        \
+  "The maximum allowed interval is "QSTR( MAX_TOD_UPDATE_USECS )" microseconds (one microsecond\n" \
+  "less than one second).\n"                                        \
   "\n"                                                                          \
   "Also note that due to host system limitations and/or design, some\n"         \
   "hosts may round up and/or coalesce short microsecond intervals to a\n"       \

comm3705.c

@@ -1158,7 +1158,7 @@ static void *telnet_thread(void *vca)
         ca->hangup = 0;
         for (;;)
         {
-            usleep(50000);
+            USLEEP(50000);
             if (ca->hangup)
                 break;
             /* read_socket has changed from 3.04 to 3.06 - we need old way */
@@ -1224,7 +1224,7 @@ static void *commadpt_thread(void *vca)
         release_lock(&ca->lock);
         if(ca->ackspeed == 0) delay = 50000 + (ca->unack_attn_count * 100000);         /* Max's reliable algorithm      */
         else delay = (ca->unack_attn_count * ca->unack_attn_count + 1) * ca->ackspeed; /* much faster but TCAM hates it */
-        usleep(min(1000000,delay));                                                    /* go to sleep, max. 1 second    */
+        USLEEP(min((int)(ONE_MILLION-1),delay));                                       /* go to sleep, max. 1 second    */
         obtain_lock(&ca->lock);
         make_sna_requests2(ca);
         make_sna_requests3(ca);

commadpt.c

@@ -1474,7 +1474,7 @@ static void *commadpt_thread(void *vca)
                 if(ca->inbfr.havedata || ca->eol_flag)
                 {
                     if (ca->term == COMMADPT_TERM_2741) {
-                        usleep(10000);
+                        USLEEP(10000);
                     }
                     ca->curpending=COMMADPT_PEND_IDLE;
                     signal_condition(&ca->ipc);

console.c

@@ -3632,7 +3632,7 @@ int prev_rlen3270;
             {
                 // "COMM: pselect() failed: %s"
                 CONERROR( HHC90508, "D", strerror( select_errno ));
-                usleep( 50000 ); // (wait a bit; maybe it'll fix itself??)
+                USLEEP( 50000 ); // (wait a bit; maybe it'll fix itself??)
             }
             continue;
 
@@ -3696,7 +3696,7 @@ int prev_rlen3270;
                 {
                     // "COMM: accept() failed: %s"
                     CONERROR( HHC90509, "D", strerror( accept_errno ));
-                    usleep( 50000 ); // (wait a bit; maybe it'll fix itself??)
+                    USLEEP( 50000 ); // (wait a bit; maybe it'll fix itself??)
                 }
                 continue;
             }

ctc_ctci.c

@@ -1092,7 +1092,7 @@ static void*  CTCI_ReadThread( void* arg )
             // Don't use sched_yield() here; use an actual non-dispatchable
             // delay instead so as to allow another [possibly lower priority]
             // thread to 'read' (remove) some packet(s) from our frame buffer.
-            usleep( CTC_DELAY_USECS );  // (wait a bit before retrying...)
+            USLEEP( CTC_DELAY_USECS );  // (wait a bit before retrying...)
         }
     }
 

ctc_lcs.c

@@ -1691,7 +1691,7 @@ static void  UpdatePortStarted( int bStarted, DEVBLK* pDEVBLK, PLCSPORT pLCSPORT
     release_lock( &pLCSPORT->PortEventLock );
 
     PTT_DEBUG( "UPDTPORT pause 150", 000, pDEVBLK->devnum, pLCSPORT->bPort );
-    usleep( 150*1000 );
+    USLEEP( 150*1000 );
 }
 
 // ====================================================================
@@ -2191,7 +2191,7 @@ static void LCS_EnqueueReplyFrame( PLCSDEV pLCSDEV, PLCSCMDHDR pReply, size_t iS
         // Wait for LCS_Read to empty the buffer...
 
         ASSERT( ENOBUFS == errno );
-        usleep( CTC_DELAY_USECS );
+        USLEEP( CTC_DELAY_USECS );
     }
     PTT_TIMING( "af repNQ", 0, iSize, 0 );
     PTT_DEBUG( "ENQ RepFrame EXIT ", pReply->bCmdCode, pDEVBLK->devnum, bPort );
@@ -2798,7 +2798,7 @@ static void LCS_EnqueueEthFrame( PLCSPORT pLCSPORT, PLCSDEV pLCSDEV, BYTE* pData
         // Wait for LCS_Read to empty the buffer...
 
         ASSERT( ENOBUFS == errno );
-        usleep( CTC_DELAY_USECS );
+        USLEEP( CTC_DELAY_USECS );
     }
     PTT_TIMING( "af enqueue", 0, iSize, 0 );
     PTT_DEBUG( "ENQ EthFrame EXIT ", 000, pDEVBLK->devnum, bPort );
@@ -4150,7 +4150,7 @@ static void*  LCS_AttnThread( void* arg)
                 {
 
                     // Wait a small (but increasing) amount of time.
-                    usleep(interval);
+                    USLEEP(interval);
 
 //??                // is there still something in our frame buffer?
 //??                if (!pLCSDEV->fDataPending && !pLCSDEV->fReplyPending)

ctc_ptp.c

@@ -2263,7 +2263,7 @@ void*  ptp_read_thread( void* arg )
                 // Don't use schedyield() here; use an actual non-dispatchable
                 // delay instead so as to allow another [possibly lower priority]
                 // thread to 'read' (remove) the packet(s) from the read buffer.
-                usleep( PTP_DELAY_USECS );  // (wait a bit before retrying...)
+                USLEEP( PTP_DELAY_USECS );  // (wait a bit before retrying...)
 
                 continue;
 

ctcadpt.c

@@ -1929,7 +1929,7 @@ static int  CTCE_Init( DEVBLK *dev, int argc, char *argv[] )
             dev->allocated = 0;
             RELEASE_DEVLOCK( dev );
             {
-                usleep( 700000 );
+                USLEEP( 700000 );
             }
             OBTAIN_DEVLOCK( dev );
             dev->allocated = 1;
@@ -2945,7 +2945,7 @@ static void*  CTCE_RecvThread( void* argp )
                     {
                         CTCE_Info.de_ready_attn_rc = device_attention( pDEVBLK, CSW_DE );
                     }
-                    while ((CTCE_Info.de_ready_attn_rc == 3) && (usleep( 100 ) == 0));
+                    while ((CTCE_Info.de_ready_attn_rc == 3) && (USLEEP( 100 ) == 0));
                 }
                 OBTAIN_DEVLOCK( pDEVBLK );
 
@@ -2995,7 +2995,7 @@ static void*  CTCE_RecvThread( void* argp )
                     // which needs to be configured using the CTCE option ATTNDELAY <nnn>
                     if( pDEVBLK->ctce_attn_delay && CTCE_Info.busy_waits == 0 )
                     {
-                        usleep( pDEVBLK->ctce_attn_delay );
+                        USLEEP( pDEVBLK->ctce_attn_delay );
                     }
 
                     CTCE_Info.working_attn_rc = device_attention( pDEVBLK, CSW_ATTN );
@@ -3014,7 +3014,7 @@ static void*  CTCE_RecvThread( void* argp )
                         {
                             i = i * 2;
                         }
-                        usleep(i);
+                        USLEEP(i);
 
                         // Cancel the ATTN in case a CCW program
                         // has started in the mean time.
@@ -3632,7 +3632,7 @@ static void*  CTCE_ConnectThread( void* argp )
         if ( rc < 0 )
         {
             close_socket( fd );
-            usleep(connect_retry_interval * 1000) ;
+            USLEEP(connect_retry_interval * 1000) ;
         }
         OBTAIN_DEVLOCK( dev );
 

dasdconv.c

@@ -195,7 +195,7 @@ static void delayed_exit (int exit_code)
 {
     /* Delay exiting is to give the system
      * time to display the error message. */
-    usleep(100000);
+    USLEEP(100000);
     exit(exit_code);
 }
 

dasdconv64.c

@@ -194,7 +194,7 @@ static void delayed_exit (int exit_code)
 {
     /* Delay exiting is to give the system
      * time to display the error message. */
-    usleep(100000);
+    USLEEP(100000);
     exit(exit_code);
 }
 

diagnose.c

@@ -877,7 +877,7 @@ U32   code;
         for (i=0; i < secs; ++i)
             SLEEP(1);       /* (sleep one second at a time) */
         if (usecs)
-            usleep(usecs);  /* (remaining microseconds, if any) */
+            USLEEP(usecs);  /* (remaining microseconds, if any) */
         break;
     }
 

dyngui.c

@@ -2177,7 +2177,7 @@ HDL_FINAL_SECTION
     if (sysblk.shutdown)
     {
         bDoneProcessing = TRUE;     // (tell main loop to stop processing)
-        usleep(100000);             // (brief delay to give GUI time
+        USLEEP(100000);             // (brief delay to give GUI time
                                     //  to display ALL shutdown msgs)
     }
 }

featall.h

@@ -70,7 +70,7 @@
 
 #define MIN_TOD_UPDATE_USECS         50 /* Min TOD updt freq (usecs) */
 #define DEF_TOD_UPDATE_USECS         50 /* Def TOD updt freq (usecs) */
-#define MAX_TOD_UPDATE_USECS    1000000 /* Max TOD updt freq (usecs) */
+#define MAX_TOD_UPDATE_USECS     999999 /* Max TOD updt freq (usecs) */
 
 #define MAX_DEVICE_THREAD_IDLE_SECS 300 /* 5 Minute thread timeout   */
 //efine OPTION_LONG_HOSTINFO            /* Detailed host & logo info */

hao.c

@@ -611,7 +611,7 @@ static void* hao_thread(void* dummy)
             // "HAO thread waiting for logger facility to become active"
             WRMSG( HHC00090, "W" );
         }
-        usleep( 50 * 1000 );    /* (wait for a bit) */
+        USLEEP( 50 * 1000 );    /* (wait for a bit) */
     }
 
     if (!sysblk.shutdown && did_waiting_msg)

hsccmd.c

@@ -745,7 +745,7 @@ static void* quit_thread( void* arg )
     // messages at least twice to ensure that the "exit"
     // command has time to be echoed to the screen.
 
-    usleep( quitdelay_usecs );
+    USLEEP( quitdelay_usecs );
 
     // Now proceed with a normal shutdown, which waits for
     // the guest to quiesce itself beforehand (if appropriate)
@@ -1987,7 +1987,7 @@ static void try_scsi_refresh( DEVBLK* dev )
     gen_parms.dev     = dev;
 
     VERIFY( dev->tmh->generic( &gen_parms ) == 0 ); // (maybe update status)
-    usleep( 10 * 1000 );                            // (let thread start/end)
+    USLEEP( 10 * 1000 );                            // (let thread start/end)
 }
 
 /*-------------------------------------------------------------------*/
@@ -7536,7 +7536,7 @@ char   **save_argv = NULL;
                          || (dev->scsw.flag3 & SCSW3_SC_PEND)))
         {
             RELEASE_DEVLOCK( dev );
-            usleep(5000);
+            USLEEP(5000);
             OBTAIN_DEVLOCK( dev );
         }
     }

hscmisc.c

@@ -1455,7 +1455,7 @@ static void do_shutdown_now()
     // (hack to prevent minor message glitch during shutdown)
     fflush( stdout );
     fflush( stderr );
-    usleep( 10000 );
+    USLEEP( 10000 );
 
     ASSERT( !sysblk.shutfini );   // (sanity check)
     sysblk.shutfini = FALSE;      // (shutdown NOT finished yet)
@@ -1467,7 +1467,7 @@ static void do_shutdown_now()
         for (n=0; sysblk.devtnbr && n < 100; ++n)
         {
             signal_condition( &sysblk.ioqcond );
-            usleep( 10000 );
+            USLEEP( 10000 );
         }
     }
 
@@ -1477,7 +1477,7 @@ static void do_shutdown_now()
     // (hack to prevent minor message glitch during shutdown)
     fflush( stdout );
     fflush( stderr );
-    usleep( 10000 );
+    USLEEP( 10000 );
 
 #if !defined( _MSVC_ )
     logger_unredirect();

hscutl.c

@@ -604,6 +604,21 @@ DLL_EXPORT void list_all_symbols()
             WRMSG( HHC02199, "I", tok->var, tok->val ? tok->val : "" );
 }
 
+/* Hercules microsecond sleep */
+DLL_EXPORT int herc_usleep( useconds_t usecs )
+{
+    int  rc;
+    if ((rc = usleep( usecs )) != 0)
+    {
+        int save_errno = errno;
+        // "Error in function %s: %s"
+        WRMSG( HHC00075, "E", "usleep()", strerror( save_errno ));
+        errno = save_errno;
+        rc = -1;
+    }
+    return rc;
+}
+
 /* Subtract 'beg_timeval' from 'end_timeval' yielding 'dif_timeval' */
 /* Return code: success == 0, error == -1 (difference was negative) */
 

hscutl.h

@@ -154,6 +154,9 @@ strlcat(char *dst, const char *src, size_t siz);
 #define STRLCPY( dst, src )     strlcpy( (dst), (src), sizeof(dst) )
 #define STRLCAT( dst, src )     strlcat( (dst), (src), sizeof(dst) )
 
+#define USLEEP( _u ) herc_usleep( _u )
+HUT_DLL_IMPORT int herc_usleep( useconds_t usecs );
+
 /* Subtract/add gettimeofday struct timeval */
 HUT_DLL_IMPORT int timeval_subtract (struct timeval *beg_timeval, struct timeval *end_timeval, struct timeval *dif_timeval);
 HUT_DLL_IMPORT int timeval_add      (struct timeval *dif_timeval, struct timeval *accum_timeval);

html/hercconf.html

@@ -1620,7 +1620,8 @@ <h3>System parameters</h3>
     When the z/Architecure Transactional-Execution Facility <i><u>is</u></i> installed and
     enabled, the minimum and default intervals are 200 and 400 microseconds.
     <p>
-    The maximum allowed interval is 1000000 microseconds (one second).
+    The maximum allowed interval is 999999 microseconds
+    (one microsecond less than one second).
     <p>
     Also note that due to host system limitations and/or design, some
     hosts may round up and/or