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From: "zilla at kayari dot org" <sourceware-bugzilla@sourceware.org> To: glibc-bugs@sources.redhat.com Subject: [Bug nptl/13002] New: robust mutex deadlocks instead of returning EOWNERDEAD Date: Sat, 16 Jul 2011 13:37:00 -0000 [thread overview] Message-ID: <bug-13002-131@http.sourceware.org/bugzilla/> (raw) http://sourceware.org/bugzilla/show_bug.cgi?id=13002 Summary: robust mutex deadlocks instead of returning EOWNERDEAD Product: glibc Version: 2.14 Status: NEW Severity: normal Priority: P2 Component: nptl AssignedTo: drepper.fsp@gmail.com ReportedBy: zilla@kayari.org Originally reported as http://bugzilla.redhat.com/show_bug.cgi?id=628608 As shown by this code, the kernel clear the robust list for the child after a fork: #include <stdio.h> #include <stddef.h> #include <stdlib.h> #include <unistd.h> #include <sys/wait.h> #include <sys/syscall.h> #include <syscall.h> int main() { void *list; size_t sz; if (syscall(__NR_get_robust_list, 0, &list, &sz)) abort(); if (!list) abort(); if (fork() == 0) { if (syscall(__NR_get_robust_list, 0, &list, &sz)) return 1; if (!list) return 2; return 0; } int status; waitpid(-1, &status, 0); if (!WIFEXITED(status)) { printf("child exited abnormally\n"); return 1; } switch(WEXITSTATUS(status)) { case 1: printf("child failed to call get_robust_list\n"); return 1; case 2: printf("child has no robust list\n"); return 1; default: printf("child exited normally\n"); } return 0; } If a parent process and child process share a robust mutex and the child exits while holding the mutex lock, when the parent tries to acquire the lock it will hang instead of being notified of the state by EOWNERDEAD. Here's a testcase which exits successfully on Solaris but deadlocks with NPTL #include <sys/types.h> #include <sys/mman.h> #include <sys/stat.h> #include <sys/wait.h> #include <pthread.h> #include <unistd.h> #include <stdlib.h> #include <errno.h> #include <stdio.h> #include <fcntl.h> void initialize(pthread_mutex_t* mtx) { pthread_mutexattr_t mtxa; if(pthread_mutexattr_init(&mtxa)) abort(); if(pthread_mutexattr_setpshared(&mtxa, PTHREAD_PROCESS_SHARED)) abort(); if(pthread_mutexattr_setrobust_np(&mtxa, PTHREAD_MUTEX_ROBUST_NP)) abort(); if(pthread_mutex_init(mtx, &mtxa)) abort(); pthread_mutexattr_destroy(&mtxa); } void set_consistent(pthread_mutex_t* mtx) { if(pthread_mutex_consistent_np(mtx)) abort(); } void lock(pthread_mutex_t* mtx) { int err; if((err = pthread_mutex_lock(mtx))) { if(EOWNERDEAD == err) { // handle abandoned mutex if(pthread_mutex_consistent_np(mtx)) abort(); } else abort(); } } void unlock(pthread_mutex_t* mtx) { if(pthread_mutex_unlock(mtx)) abort(); } pid_t spawn(int(*fn)()) { // fork a child process pid_t pid = fork(); switch(pid) { case 0: exit(fn()); case -1: abort(); default: return pid; } } char const shared_file[] = "shared_file"; void* open_shared_file() { int fd = open(shared_file, O_CREAT | O_RDWR, (mode_t)0666); if(fd < 0) abort(); struct stat st; if(fstat(fd, &st)) abort(); int new_file = !st.st_size; if (new_file) if(ftruncate(fd, sizeof(pthread_mutex_t))) abort(); void* mem = mmap(NULL, sizeof(pthread_mutex_t), PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); close(fd); if(MAP_FAILED == mem) abort(); if (new_file) initialize((pthread_mutex_t*)mem); return mem; } int process_1() { unsigned pid = getpid(); printf("%u: process 1\n", pid); pthread_mutex_t* m = (pthread_mutex_t*)open_shared_file(); printf("%u: locking mutex...\n", pid); lock(m); printf("%u: exiting\n", pid); return 0; } int process_2() { unsigned pid = getpid(); printf("%u: process 2\n", pid); pthread_mutex_t* m = (pthread_mutex_t*)open_shared_file(); printf("%u: locking mutex...\n", pid); lock(m); printf("%u: mutex locked\n", pid); unlock(m); return 0; } int main(int ac, char** av) { // fork process_1 and wait till it terminates pid_t child; unlink(shared_file); int child_status; child = spawn(process_1); if(-1 == waitpid(child, &child_status, 0)) abort(); // now do process_2 return process_2(); } -- Configure bugmail: http://sourceware.org/bugzilla/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are on the CC list for the bug.
next reply other threads:[~2011-07-16 13:37 UTC|newest] Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top 2011-07-16 13:37 zilla at kayari dot org [this message] 2011-07-20 16:26 ` [Bug nptl/13002] " drepper.fsp at gmail dot com 2011-07-20 17:21 ` zilla at kayari dot org 2011-08-10 4:39 ` wang.deqiang1 at zte dot com.cn 2014-02-16 16:59 ` jackie.rosen at hushmail dot com 2014-05-28 19:46 ` schwab at sourceware dot org 2014-05-28 19:47 ` schwab at sourceware dot org 2014-06-27 12:55 ` fweimer at redhat dot com
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