[Rd] Sys.sleep() burns up CPU on Solaris 8

From: Stephen C. Pope <scp_at_predict.com>
Date: Sat 01 Apr 2006 - 06:31:35 GMT


I noticed that R was burning up 100% of a CPU when a call to Sys.sleep() was made. Upon investigation, I discovered that R_checkActivityEx() in src/unix/sys-std.c was putting the entire timeout (in usec) into the struct timeval tv_usec member, leaving tv_sec set to 0.

I don't know about other unix variants, but Solaris requires that the timeout value be normalized (i.e. 0 <= tv_usec < 1000000). Because a value greater than 1000000 was being placed in tv_usec, select() was returning an error (EINVAL) immediately, causing R_checkActivityEx() to return immediately. This caused do_syssleep() to loop continuously until the desired elapsed time had evolved. A rather sleepless sleep ;-).

The following patch against R-2.2.1 fixes the problem. Note that the test of the return value for R_SelectEx() was also incorrect; although harmless, it was treating the error return (-1) as a successful return.

stephen pope
scp@predict.com

Here's the patch.

build_main@mambo:/vobs/products/R> gdiff -ub src/unix/sys-std.c@@/main/3 src/unix/sys-std.c
--- src/unix/sys-std.c@@/main/3 Thu Jan 12 11:39:55 2006 +++ src/unix/sys-std.c Fri Mar 31 23:12:16 2006 @@ -294,13 +294,13 @@

         else onintr();
      }


- tv.tv_sec = 0;
- tv.tv_usec = usec;

+ tv.tv_sec = usec/1000000;
+ tv.tv_usec = usec % 1000000;
      maxfd = setSelectMask(R_InputHandlers, &readMask);
      if (ignore_stdin)
         FD_CLR(fileno(stdin), &readMask);
      if (R_SelectEx(maxfd+1, &readMask, NULL, NULL,

- (usec >= 0) ? &tv : NULL, intr))
+ (usec >= 0) ? &tv : NULL, intr) > 0)
return(&readMask); else return(NULL); ______________________________________________
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https://stat.ethz.ch/mailman/listinfo/r-devel Received on Sat Apr 01 16:54:20 2006

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