cvs commit: src/sys/sys kse.h proc.h signalvar.h src/sys/kern kern_exit.c kern_sig.c kern_thread.c

David Xu davidxu at
Tue Jul 13 00:20:11 PDT 2004

davidxu     2004-07-13 07:20:10 UTC

  FreeBSD src repository

  Modified files:
    sys/sys              kse.h proc.h signalvar.h 
    sys/kern             kern_exit.c kern_sig.c kern_thread.c 
  Add code to support debugging threaded process.
  1. Add tm_lwpid into kse_thr_mailbox to indicate which kernel
     thread current user thread is running on. Add tm_dflags into
     kse_thr_mailbox, the flags is written by debugger, it tells
     UTS and kernel what should be done when the process is being
     debugged, current, there two flags TMDF_SSTEP and TMDF_DONOTRUNUSER.
     TMDF_SSTEP is used to tell kernel to turn on single stepping,
     or turn off if it is not set.
     TMDF_DONOTRUNUSER is used to tell kernel to schedule upcall
     whenever possible, to UTS, it means do not run the user thread
     until debugger clears it, this behaviour is necessary because
     gdb wants to resume only one thread when the thread's pc is
     at a breakpoint, and thread needs to go forward, in order to
     avoid other threads sneak pass the breakpoints, it needs to remove
     breakpoint, only wants one thread to go. Also, add km_lwp to
     kse_mailbox, the lwp id is copied to kse_thr_mailbox at context
     switch time when process is not being debugged, so when process
     is attached, debugger can map kernel thread to user thread.
  2. Add p_xthread to proc strcuture and td_xsig to thread structure.
     p_xthread is used by a thread when it wants to report event
     to debugger, every thread can set the pointer, especially, when
     it is used in ptracestop, it is the last thread reporting event
     will win the race. Every thread has a td_xsig to exchange signal
     with debugger, thread uses TDF_XSIG flag to indicate it is reporting
     signal to debugger, if the flag is not cleared, thread will keep
     retrying until it is cleared by debugger, p_xthread may be
     used by debugger to indicate CURRENT thread. The p_xstat is still
     in proc structure to keep wait() to work, in future, we may
     just use td_xsig.
  3. Add TDF_DBSUSPEND flag, the flag is used by debugger to suspend
     a thread. When process stops, debugger can set the flag for
     thread, thread will check the flag in thread_suspend_check,
     enters a loop, unless it is cleared by debugger, process is
     detached or process is existing. The flag is also checked in
     ptracestop, so debugger can temporarily suspend a thread even
     if the thread wants to exchange signal.
  4. Current, in ptrace, we always resume all threads, but if a thread
     has already a TDF_DBSUSPEND flag set by debugger, it won't run.
  Encouraged by: marcel, julian, deischen
  Revision  Changes    Path
  1.241     +1 -1      src/sys/kern/kern_exit.c
  1.284     +81 -44    src/sys/kern/kern_sig.c
  1.187     +4 -1      src/sys/kern/kern_thread.c
  1.23      +31 -21    src/sys/sys/kse.h
  1.386     +5 -2      src/sys/sys/proc.h
  1.67      +1 -1      src/sys/sys/signalvar.h

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