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The signal handler reads the global session pointer from an async- signal context while another thread installs/removes the session via set/remove_signal_handlers. Use std::atomic<fuse_session*> with acquire/release ordering so the handler either sees NULL or a fully published session, never a torn pointer.
78 lines
2 KiB
C++
78 lines
2 KiB
C++
/*
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FUSE: Filesystem in Userspace
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Copyright (C) 2001-2007 Miklos Szeredi <miklos@szeredi.hu>
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This program can be distributed under the terms of the GNU LGPLv2.
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See the file COPYING.LIB
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*/
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#include "fuse_lowlevel.h"
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#include <atomic>
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#include <stdio.h>
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#include <string.h>
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#include <signal.h>
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static std::atomic<fuse_session*> g_fuse_instance{nullptr};
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static
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void
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exit_handler(int sig)
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{
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(void)sig;
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struct fuse_session *instance;
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instance = g_fuse_instance.load(std::memory_order_acquire);
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if(instance)
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fuse_session_exit(instance);
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}
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static int set_one_signal_handler(int sig, void (*handler)(int), int remove)
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{
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struct sigaction sa;
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struct sigaction old_sa;
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memset(&sa, 0, sizeof(struct sigaction));
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sa.sa_handler = remove ? SIG_DFL : handler;
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sigemptyset(&(sa.sa_mask));
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sa.sa_flags = 0;
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if (sigaction(sig, NULL, &old_sa) == -1) {
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perror("fuse: cannot get old signal handler");
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return -1;
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}
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if (old_sa.sa_handler == (remove ? handler : SIG_DFL) &&
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sigaction(sig, &sa, NULL) == -1) {
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perror("fuse: cannot set signal handler");
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return -1;
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}
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return 0;
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}
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int fuse_set_signal_handlers(struct fuse_session *se)
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{
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if((set_one_signal_handler(SIGINT, exit_handler, 0) == -1) ||
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(set_one_signal_handler(SIGTERM, exit_handler, 0) == -1) ||
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(set_one_signal_handler(SIGQUIT, exit_handler, 0) == -1) ||
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(set_one_signal_handler(SIGPIPE, SIG_IGN, 0) == -1))
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return -1;
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g_fuse_instance.store(se,std::memory_order_release);
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return 0;
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}
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void fuse_remove_signal_handlers(struct fuse_session *se)
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{
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set_one_signal_handler(SIGINT, exit_handler, 1);
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set_one_signal_handler(SIGTERM, exit_handler, 1);
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set_one_signal_handler(SIGQUIT, exit_handler, 1);
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set_one_signal_handler(SIGPIPE, SIG_IGN, 1);
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if(g_fuse_instance.load(std::memory_order_acquire) != se)
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fprintf(stderr,"mergerfs: fuse_remove_signal_handlers: unknown session\n");
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else
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g_fuse_instance.store(nullptr,std::memory_order_release);
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}
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