Patch that provides true single step for multi-threaded /proc based processes (Tru64 5.1A)

[Tonny Madsen]

Howdy everybody,
 
In the company I work for, we use Tru64 5.1A as the main development and
deployment platform. The rather poor support for this platform in gdb is
the cause of problems and we have devoted some resources to find a solve
the most serious og these (as seem by us).
 
Currently we use the mdebugread patch as weel to handle the special
sections in native Tru64 5.1A shared libraties.
 
One problem we have been bitten by a number of times was the lack of
true single step support for multi-threaded processes. As Tru64 5.1A is
/proc based, the functions in question are proc_run_process and
procfs_resume. In these functions single step support is only
implemented for the new /proc API. Please note that we use multi-CPU
machine so we are bitten by this often!
 
The following patch will add support for the ioctl PIOCTRUN (if defined)
in proc_run_process.
 
Please comment on this if you see anything wrong with it.
 
I don't know if the patch is general for all /proc based architectures,
but I currently expect so.
 
/tonny
 

--- gdb/procfs.c-orig 2002-02-14 02:57:36.000000000 +0100
+++ gdb/procfs.c 2002-06-26 10:16:34.000000000 +0200
@@ -1748,6 +1748,30 @@
win = (write (pi->ctl_fd, (char *) &cmd, sizeof (cmd)) == sizeof (cmd));
}
#else /* ioctl method */
+#ifdef PIOCTRUN
+ /*
+ * If we single step AND the PIOCTRUN ioctl is supported, then use
+ * this. This cures the problem when single stepping a
+ * multi-threaded program, when all the other threads (than the
+ * current single stepped one), may run free while single stepping.
+ *
+ * Note that only the PRSTEP flag is of interrest here (PRCFAULT and
+ * PRCSIG are not allowed).
+ */
+ if (step) {
+ /* Structure from proc(4) on Tru64 5.1A. */
+ struct {
+ long pr_count; /* number of threads to run */
+ tid_t pr_error_thread; /* set by kernel if error is detected */
+ struct prrun thread_1; /* prrun struct, containing thread ID of 1st
thread to run in thread_1.pr_tid */
+ } prrun;
+ memset(&prrun, 0, sizeof (prrun));
+ prrun.pr_count = 1;
+ prrun.thread_1.pr_flags = PRSTEP;
+ prrun.thread_1.pr_tid = pi->prstatus.pr_tid;
+ win = (ioctl (pi->ctl_fd, PIOCTRUN, &prrun) >= 0);
+ } else
+#endif
{
prrun_t prrun;

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