-/* Multi-threaded debugging support for Linux (LWP layer).
+/* Multi-threaded debugging support for GNU/Linux (LWP layer).
Copyright 2000, 2001 Free Software Foundation, Inc.
This file is part of GDB.
#include "defs.h"
#include "gdb_assert.h"
+#include "gdb_string.h"
#include <errno.h>
#include <signal.h>
#include <sys/ptrace.h>
static int debug_lin_lwp;
extern const char *strsignal (int sig);
-/* On Linux there are no real LWP's. The closest thing to LWP's are
- processes sharing the same VM space. A multi-threaded process is
- basically a group of such processes. However, such a grouping is
- almost entirely a user-space issue; the kernel doesn't enforce such
- a grouping at all (this might change in the future). In general,
- we'll rely on the threads library (i.e. the LinuxThreads library)
- to provide such a grouping.
+/* On GNU/Linux there are no real LWP's. The closest thing to LWP's
+ are processes sharing the same VM space. A multi-threaded process
+ is basically a group of such processes. However, such a grouping
+ is almost entirely a user-space issue; the kernel doesn't enforce
+ such a grouping at all (this might change in the future). In
+ general, we'll rely on the threads library (i.e. the GNU/Linux
+ Threads library) to provide such a grouping.
It is perfectly well possible to write a multi-threaded application
without the assistance of a threads library, by using the clone
system call directly. This module should be able to give some
rudimentary support for debugging such applications if developers
specify the CLONE_PTRACE flag in the clone system call, and are
- using Linux 2.4 or above.
+ using the Linux kernel 2.4 or above.
- Note that there are some peculiarities in Linux that affect this
- code:
+ Note that there are some peculiarities in GNU/Linux that affect
+ this code:
- In general one should specify the __WCLONE flag to waitpid in
order to make it report events for any of the cloned processes
(and leave it out for the initial process). However, if a cloned
process has exited the exit status is only reported if the
- __WCLONE flag is absent. Linux 2.4 has a __WALL flag, but we
- cannot use it since GDB must work on older systems too.
+ __WCLONE flag is absent. Linux kernel 2.4 has a __WALL flag, but
+ we cannot use it since GDB must work on older systems too.
- When a traced, cloned process exits and is waited for by the
debugger, the kernel reassigns it to the original parent and
- keeps it around as a "zombie". Somehow, the LinuxThreads library
- doesn't notice this, which leads to the "zombie problem": When
- debugged a multi-threaded process that spawns a lot of threads
- will run out of processes, even if the threads exit, because the
- "zombies" stay around. */
+ keeps it around as a "zombie". Somehow, the GNU/Linux Threads
+ library doesn't notice this, which leads to the "zombie problem":
+ When debugged a multi-threaded process that spawns a lot of
+ threads will run out of processes, even if the threads exit,
+ because the "zombies" stay around. */
/* Structure describing a LWP. */
struct lwp_info
}
\f
-/* Implementation of the PREPARE_TO_PROCEED hook for the Linux LWP
+/* Implementation of the PREPARE_TO_PROCEED hook for the GNU/Linux LWP
layer.
Note that this implementation is potentially redundant now that
gdb_assert (is_lwp (ptid));
+ /* Make sure SIGCHLD is blocked. We don't want SIGCHLD events
+ to interrupt either the ptrace() or waitpid() calls below. */
+ if (! sigismember (&blocked_mask, SIGCHLD))
+ {
+ sigaddset (&blocked_mask, SIGCHLD);
+ sigprocmask (SIG_BLOCK, &blocked_mask, NULL);
+ }
+
if (verbose)
printf_filtered ("[New %s]\n", target_pid_to_str (ptid));
if (ptrace (PTRACE_ATTACH, GET_LWP (ptid), 0, 0) < 0)
error ("Can't attach %s: %s", target_pid_to_str (ptid),
- strerror (errno));
+ safe_strerror (errno));
pid = waitpid (GET_LWP (ptid), &status, 0);
if (pid == -1 && errno == ECHILD)
lp->stopped = 1;
}
+ else
+ {
+ /* We assume that the LWP representing the original process
+ is already stopped. Mark it as stopped in the data structure
+ that the lin-lwp layer uses to keep track of threads. Note
+ that this won't have already been done since the main thread
+ will have, we assume, been stopped by an attach from a
+ different layer. */
+ lp->stopped = 1;
+ }
}
static void
if (ptrace (PTRACE_CONT, GET_LWP (lp->ptid), 0,
WSTOPSIG (lp->status)) < 0)
error ("Can't continue %s: %s", target_pid_to_str (lp->ptid),
- strerror (errno));
+ safe_strerror (errno));
lp->stopped = 0;
lp->signalled = 0;
if (ptrace (PTRACE_DETACH, GET_LWP (lp->ptid), 0,
WSTOPSIG (lp->status)) < 0)
error ("Can't detach %s: %s", target_pid_to_str (lp->ptid),
- strerror (errno));
+ safe_strerror (errno));
delete_lwp (lp->ptid);
}
struct lwp_info *lp;
int resume_all;
- /* Apparently the interpretation of PID is dependent on STEP: If
- STEP is non-zero, a specific PID means `step only this process
- id'. But if STEP is zero, then PID means `continue *all*
- processes, but give the signal only to this one'. */
- resume_all = (PIDGET (ptid) == -1) || !step;
+ /* A specific PTID means `step only this process id'. */
+ resume_all = (PIDGET (ptid) == -1);
if (resume_all)
iterate_over_lwps (resume_set_callback, NULL);
clear_sigio_trap ();
clear_sigint_trap ();
}
- while (pid == -1 && errno == EINTR);
+ while (pid == -1 && save_errno == EINTR);
if (pid == -1)
{
- warning ("Child process unexpectedly missing: %s", strerror (errno));
+ warning ("Child process unexpectedly missing: %s", safe_strerror (errno));
/* Claim it exited with unknown signal. */
ourstatus->kind = TARGET_WAITKIND_SIGNALLED;
add_show_from_set (add_set_cmd ("lin-lwp", no_class, var_zinteger,
(char *) &debug_lin_lwp,
- "Set debugging of linux lwp module.\n\
+ "Set debugging of GNU/Linux lwp module.\n\
Enables printf debugging output.\n",
&setdebuglist),
&showdebuglist);
\f
/* FIXME: kettenis/2000-08-26: The stuff on this page is specific to
- the LinuxThreads library and therefore doesn't really belong here. */
+ the GNU/Linux Threads library and therefore doesn't really belong
+ here. */
/* Read variable NAME in the target and return its value if found.
Otherwise return zero. It is assumed that the type of the variable
sigaddset (set, restart);
sigaddset (set, cancel);
- /* The LinuxThreads library makes terminating threads send a special
- "cancel" signal instead of SIGCHLD. Make sure we catch those (to
- prevent them from terminating GDB itself, which is likely to be
- their default action) and treat them the same way as SIGCHLD. */
+ /* The GNU/Linux Threads library makes terminating threads send a
+ special "cancel" signal instead of SIGCHLD. Make sure we catch
+ those (to prevent them from terminating GDB itself, which is
+ likely to be their default action) and treat them the same way as
+ SIGCHLD. */
action.sa_handler = sigchld_handler;
sigemptyset (&action.sa_mask);
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