4dbed85a35
Sometimes when UML is debugged gdb miss breakpoints. When process traced by gdb do fork, debugger remove breakpoints from child address space. There is possibility to trace more than one fork, but this not work with UML, I guess (only guess) there is a deadlock - gdb waits for UML and UML waits for gdb. When clone() is called with SIGCHLD and CLONE_VM flags, gdb see this as PTRACE_EVENT_FORK not as PTRACE_EVENT_CLONE and remove breakpoints from child and at the same time from traced process, because either have the same address space. Maybe it is possible to do fix in gdb, but I'm not sure if there is easy way to find out if traced and child processes share memory. So I do fix for UML, it simply do not call clone() with both SIGCHLD and CLONE_VM flags together. Additionally __WALL flag is used for waitpid() to assure not miss clone and normal process events. [ jdike - checkpatch fixes ] Signed-off-by: Stanislaw Gruszka <stf_xl@wp.pl> Signed-off-by: Jeff Dike <jdike@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
68 lines
1.3 KiB
C
68 lines
1.3 KiB
C
/*
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* Copyright (C) 2000, 2001, 2002 Jeff Dike (jdike@karaya.com)
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* Copyright (C) 2001 Ridgerun,Inc (glonnon@ridgerun.com)
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* Licensed under the GPL
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*/
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#include <stddef.h>
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#include <unistd.h>
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#include <errno.h>
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#include <sched.h>
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#include <signal.h>
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#include <string.h>
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#include <netinet/in.h>
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#include <sys/time.h>
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#include <sys/socket.h>
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#include <sys/mman.h>
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#include <sys/param.h>
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#include "asm/types.h"
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#include "kern_util.h"
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#include "user.h"
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#include "ubd_user.h"
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#include "os.h"
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#include "cow.h"
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#include <endian.h>
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#include <byteswap.h>
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void ignore_sigwinch_sig(void)
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{
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signal(SIGWINCH, SIG_IGN);
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}
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int start_io_thread(unsigned long sp, int *fd_out)
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{
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int pid, fds[2], err;
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err = os_pipe(fds, 1, 1);
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if(err < 0){
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printk("start_io_thread - os_pipe failed, err = %d\n", -err);
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goto out;
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}
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kernel_fd = fds[0];
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*fd_out = fds[1];
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err = os_set_fd_block(*fd_out, 0);
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if (err) {
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printk("start_io_thread - failed to set nonblocking I/O.\n");
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goto out_close;
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}
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pid = clone(io_thread, (void *) sp, CLONE_FILES | CLONE_VM, NULL);
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if(pid < 0){
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err = -errno;
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printk("start_io_thread - clone failed : errno = %d\n", errno);
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goto out_close;
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}
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return(pid);
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out_close:
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os_close_file(fds[0]);
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os_close_file(fds[1]);
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kernel_fd = -1;
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*fd_out = -1;
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out:
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return err;
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}
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