litmus-rt.git - The LITMUS^RT kernel.

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author	Anton Blanchard <anton@samba.org>	2010-04-06 07:42:38 -0400
committer	Rusty Russell <rusty@rustcorp.com.au>	2010-04-07 20:16:20 -0400
commit	320718ee074acce5ffced6506cb51af1388942aa (patch)
tree	0c57b9337452263e8f032cd0f37069f70921c490 /include/linux/stacktrace.h
parent	b7a413015d2986edf020fba765c906cc9cbcbfc9 (diff)

hvc_console: Fix race between hvc_close and hvc_remove

I don't claim to understand the tty layer, but it seems like hvc_open and hvc_close should be balanced in their kref reference counting. Right now we get a kref every call to hvc_open: if (hp->count++ > 0) { tty_kref_get(tty); <----- here spin_unlock_irqrestore(&hp->lock, flags); hvc_kick(); return 0; } /* else count == 0 */ tty->driver_data = hp; hp->tty = tty_kref_get(tty); <------ or here if hp->count was 0 But hvc_close has: tty_kref_get(tty); if (--hp->count == 0) { ... /* Put the ref obtained in hvc_open() */ tty_kref_put(tty); ... } tty_kref_put(tty); Since the outside kref get/put balance we only do a single kref_put when count reaches 0. The patch below changes things to call tty_kref_put once for every hvc_close call, and with that my machine boots fine. Signed-off-by: Anton Blanchard <anton@samba.org> Acked-by: Amit Shah <amit.shah@redhat.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

Diffstat (limited to 'include/linux/stacktrace.h')

0 files changed, 0 insertions, 0 deletions

/* * RT-Mutex-tester: scriptable tester for rt mutexes * * started by Thomas Gleixner: * * Copyright (C) 2006, Timesys Corp., Thomas Gleixner <tglx@timesys.com> * */ #include <linux/kthread.h> #include <linux/module.h> #include <linux/sched.h> #include <linux/smp_lock.h> #include <linux/spinlock.h> #include <linux/sysdev.h> #include <linux/timer.h> #include <linux/freezer.h> #include "rtmutex.h" #define MAX_RT_TEST_THREADS 8 #define MAX_RT_TEST_MUTEXES 8 static spinlock_t rttest_lock; static atomic_t rttest_event; struct test_thread_data { int opcode; int opdata; int mutexes[MAX_RT_TEST_MUTEXES]; int bkl; int event; struct sys_device sysdev; }; static struct test_thread_data thread_data[MAX_RT_TEST_THREADS]; static struct task_struct *threads[MAX_RT_TEST_THREADS]; static struct rt_mutex mutexes[MAX_RT_TEST_MUTEXES]; enum test_opcodes { RTTEST_NOP = 0, RTTEST_SCHEDOT, /* 1 Sched other, data = nice */ RTTEST_SCHEDRT, /* 2 Sched fifo, data = prio */ RTTEST_LOCK, /* 3 Lock uninterruptible, data = lockindex */ RTTEST_LOCKNOWAIT, /* 4 Lock uninterruptible no wait in wakeup, data = lockindex */ RTTEST_LOCKINT, /* 5 Lock interruptible, data = lockindex */ RTTEST_LOCKINTNOWAIT, /* 6 Lock interruptible no wait in wakeup, data = lockindex */ RTTEST_LOCKCONT, /* 7 Continue locking after the wakeup delay */ RTTEST_UNLOCK, /* 8 Unlock, data = lockindex */ RTTEST_LOCKBKL, /* 9 Lock BKL */ RTTEST_UNLOCKBKL, /* 10 Unlock BKL */ RTTEST_SIGNAL, /* 11 Signal other test thread, data = thread id */ RTTEST_RESETEVENT = 98, /* 98 Reset event counter */ RTTEST_RESET = 99, /* 99 Reset all pending operations */ }; static int handle_op(struct test_thread_data *td, int lockwakeup) { int i, id, ret = -EINVAL; switch(td->opcode) { case RTTEST_NOP: return 0; case RTTEST_LOCKCONT: td->mutexes[td->opdata] = 1; td->event = atomic_add_return(1, &rttest_event); return 0; case RTTEST_RESET: for (i = 0; i < MAX_RT_TEST_MUTEXES; i++) { if (td->mutexes[i] == 4) { rt_mutex_unlock(&mutexes[i]); td->mutexes[i] = 0; } } if (!lockwakeup && td->bkl == 4) { unlock_kernel(); td->bkl = 0; } return 0; case RTTEST_RESETEVENT: atomic_set(&rttest_event, 0); return 0; default: if (lockwakeup) return ret; } switch(td->opcode) { case RTTEST_LOCK: case RTTEST_LOCKNOWAIT: id = td->opdata; if (id < 0 || id >= MAX_RT_TEST_MUTEXES) return ret; td->mutexes[id] = 1; td->event = atomic_add_return(1, &rttest_event); rt_mutex_lock(&mutexes[id]); td->event = atomic_add_return(1, &rttest_event); td->mutexes[id] = 4; return 0; case RTTEST_LOCKINT: case RTTEST_LOCKINTNOWAIT: id = td->opdata; if (id < 0 || id >= MAX_RT_TEST_MUTEXES) return ret; td->mutexes[id] = 1; td->event = atomic_add_return(1, &rttest_event); ret = rt_mutex_lock_interruptible(&mutexes[id], 0); td->event = atomic_add_return(1, &rttest_event); td->mutexes[id] = ret ? 0 : 4; return ret ? -EINTR : 0; case RTTEST_UNLOCK: id = td->opdata; if (id < 0 || id >= MAX_RT_TEST_MUTEXES || td->mutexes[id] != 4) return ret; td->event = atomic_add_return(1, &rttest_event); rt_mutex_unlock(&mutexes[id]); td->event = atomic_add_return(1, &rttest_event); td->mutexes[id] = 0; return 0; case RTTEST_LOCKBKL: if (td->bkl) return 0; td->bkl = 1; lock_kernel(); td->bkl = 4; return 0; case RTTEST_UNLOCKBKL: if (td->bkl != 4) break; unlock_kernel(); td->bkl = 0; return 0; default: break; } return ret; } /* * Schedule replacement for rtsem_down(). Only called for threads with * PF_MUTEX_TESTER set. * * This allows us to have finegrained control over the event flow. * */ void schedule_rt_mutex_test(struct rt_mutex *mutex) { int tid, op, dat; struct test_thread_data *td; /* We have to lookup the task */ for (tid = 0; tid < MAX_RT_TEST_THREADS; tid++) { if (threads[tid] == current) break; } BUG_ON(tid == MAX_RT_TEST_THREADS); td = &thread_data[tid]; op = td->opcode; dat = td->opdata; switch (op) { case RTTEST_LOCK: case RTTEST_LOCKINT: case RTTEST_LOCKNOWAIT: case RTTEST_LOCKINTNOWAIT: if (mutex != &mutexes[dat]) break; if (td->mutexes[dat] != 1) break; td->mutexes[dat] = 2; td->event = atomic_add_return(1, &rttest_event); break; case RTTEST_LOCKBKL: default: break; } schedule(); switch (op) { case RTTEST_LOCK: case RTTEST_LOCKINT: if (mutex != &mutexes[dat]) return; if (td->mutexes[dat] != 2) return; td->mutexes[dat] = 3; td->event = atomic_add_return(1, &rttest_event); break; case RTTEST_LOCKNOWAIT: case RTTEST_LOCKINTNOWAIT: if (mutex != &mutexes[dat]) return; if (td->mutexes[dat] != 2) return; td->mutexes[dat] = 1; td->event = atomic_add_return(1, &rttest_event); return; case RTTEST_LOCKBKL: return; default: return; } td->opcode = 0; for (;;) { set_current_state(TASK_INTERRUPTIBLE); if (td->opcode > 0) { int ret; set_current_state(TASK_RUNNING); ret = handle_op(td, 1); set_current_state(TASK_INTERRUPTIBLE); if (td->opcode == RTTEST_LOCKCONT) break; td->opcode = ret; } /* Wait for the next command to be executed */ schedule(); } /* Restore previous command and data */ td->opcode = op; td->opdata = dat; } static int test_func(void *data) { struct test_thread_data *td = data; int ret; current->flags |= PF_MUTEX_TESTER; set_freezable(); allow_signal(SIGHUP); for(;;) { set_current_state(TASK_INTERRUPTIBLE); if (td->opcode > 0) { set_current_state(TASK_RUNNING); ret = handle_op(td, 0); set_current_state(TASK_INTERRUPTIBLE); td->opcode = ret; } /* Wait for the next command to be executed */ schedule(); try_to_freeze(); if (signal_pending(current)) flush_signals(current); if(kthread_should_stop()) break; } return 0; } /** * sysfs_test_command - interface for test commands * @dev: thread reference * @buf: command for actual step * @count: length of buffer * * command syntax: * * opcode:data */ static ssize_t sysfs_test_command(struct sys_device *dev, struct sysdev_attribute *attr, const char *buf, size_t count) { struct sched_param schedpar; struct test_thread_data *td; char cmdbuf[32]; int op, dat, tid, ret; td = container_of(dev, struct test_thread_data, sysdev); tid = td->sysdev.id; /* strings from sysfs write are not 0 terminated! */ if (count >= sizeof(cmdbuf)) return -EINVAL; /* strip of \n: */ if (buf[count-1] == '\n') count--; if (count < 1) return -EINVAL; memcpy(cmdbuf, buf, count); cmdbuf[count] = 0; if (sscanf(cmdbuf, "%d:%d", &op, &dat) != 2) return -EINVAL; switch (op) { case RTTEST_SCHEDOT: schedpar.sched_priority = 0; ret = sched_setscheduler(threads[tid], SCHED_NORMAL, &schedpar); if (ret) return ret; set_user_nice(current, 0); break; case RTTEST_SCHEDRT: schedpar.sched_priority = dat; ret = sched_setscheduler(threads[tid], SCHED_FIFO, &schedpar); if (ret) return ret; break; case RTTEST_SIGNAL: send_sig(SIGHUP, threads[tid], 0); break; default: if (td->opcode > 0) return -EBUSY; td->opdata = dat; td->opcode = op; wake_up_process(threads[tid]); } return count; } /** * sysfs_test_status - sysfs interface for rt tester * @dev: thread to query * @buf: char buffer to be filled with thread status info */ static ssize_t sysfs_test_status(struct sys_device *dev, struct sysdev_attribute *attr, char *buf) { struct test_thread_data *td; struct task_struct *tsk; char *curr = buf; int i; td = container_of(dev, struct test_thread_data, sysdev); tsk = threads[td->sysdev.id]; spin_lock(&rttest_lock); curr += sprintf(curr, "O: %4d, E:%8d, S: 0x%08lx, P: %4d, N: %4d, B: %p, K: %d, M:", td->opcode, td->event, tsk->state, (MAX_RT_PRIO - 1) - tsk->prio, (MAX_RT_PRIO - 1) - tsk->normal_prio, tsk->pi_blocked_on, td->bkl); for (i = MAX_RT_TEST_MUTEXES - 1; i >=0 ; i--) curr += sprintf(curr, "%d", td->mutexes[i]); spin_unlock(&rttest_lock); curr += sprintf(curr, ", T: %p, R: %p\n", tsk, mutexes[td->sysdev.id].owner); return curr - buf; } static SYSDEV_ATTR(status, 0600, sysfs_test_status, NULL); static SYSDEV_ATTR(command, 0600, NULL, sysfs_test_command); static struct sysdev_class rttest_sysclass = { .name = "rttest", }; static int init_test_thread(int id) { thread_data[id].sysdev.cls = &rttest_sysclass; thread_data[id].sysdev.id = id; threads[id] = kthread_run(test_func, &thread_data[id], "rt-test-%d", id); if (IS_ERR(threads[id])) return PTR_ERR(threads[id]); return sysdev_register(&thread_data[id].sysdev); } static int init_rttest(void) { int ret, i; spin_lock_init(&rttest_lock); for (i = 0; i < MAX_RT_TEST_MUTEXES; i++) rt_mutex_init(&mutexes[i]); ret = sysdev_class_register(&rttest_sysclass); if (ret) return ret; for (i = 0; i < MAX_RT_TEST_THREADS; i++) { ret = init_test_thread(i); if (ret) break; ret = sysdev_create_file(&thread_data[i].sysdev, &attr_status); if (ret) break; ret = sysdev_create_file(&thread_data[i].sysdev, &attr_command); if (ret) break; } printk("Initializing RT-Tester: %s\n", ret ? "Failed" : "OK" ); return ret; } device_initcall(init_rttest);


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