The use of blocking notifier by _cpu_up and _cpu_down in cpu.c has two problem. 1/ An interaction with the workqueue notifier causes lockdep to spit a warning. 2/ A notifier could conceivable be added or removed while _cpu_up or _cpu_down are in process. As each notifier is called twice (prepare then commit/abort) this could be unhealthy. To fix to we simply take cpu_add_remove_lock while adding or removing notifiers to/from the list. This makes the 'blocking' usage unnecessary as all accesses to cpu_chain are now protected by cpu_add_remove_lock. So change "blocking" to "raw" in all relevant places. This fixes 1.
Showing the changes to kernel/cpu.c (1 of 1 file). Show all
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| @@ -19,7 +19,7 @@ · 18 unmodified lines | ||
| 19 | 19 | static DEFINE_MUTEX(cpu_add_remove_lock); |
| 20 | 20 | static DEFINE_MUTEX(cpu_bitmask_lock); |
| 21 | 21 | |
| 22 | −static __cpuinitdata BLOCKING_NOTIFIER_HEAD(cpu_chain); | |
| 22 | +static __cpuinitdata RAW_NOTIFIER_HEAD(cpu_chain); | |
| 23 | 23 | |
| 24 | 24 | /* If set, cpu_up and cpu_down will return -EBUSY and do nothing. |
| 25 | 25 | * Should always be manipulated under cpu_add_remove_lock |
| @@ -68,7 +68,11 @@ EXPORT_SYMBOL_GPL(unlock_cpu_hotplug); · 42 unmodified lines | ||
| 68 | 68 | /* Need to know about CPUs going up/down? */ |
| 69 | 69 | int __cpuinit register_cpu_notifier(struct notifier_block *nb) |
| 70 | 70 | { |
| 71 | − return blocking_notifier_chain_register(&cpu_chain, nb); | |
| 71 | + int ret; | |
| 72 | + mutex_lock(&cpu_add_remove_lock); | |
| 73 | + ret = raw_notifier_chain_register(&cpu_chain, nb); | |
| 74 | + mutex_unlock(&cpu_add_remove_lock); | |
| 75 | + return ret; | |
| 72 | 76 | } |
| 73 | 77 | |
| 74 | 78 | #ifdef CONFIG_HOTPLUG_CPU |
| @@ -77,7 +81,9 @@ EXPORT_SYMBOL(register_cpu_notifier); · 2 unmodified lines | ||
| 77 | 81 | |
| 78 | 82 | void unregister_cpu_notifier(struct notifier_block *nb) |
| 79 | 83 | { |
| 80 | − blocking_notifier_chain_unregister(&cpu_chain, nb); | |
| 84 | + mutex_lock(&cpu_add_remove_lock); | |
| 85 | + raw_notifier_chain_unregister(&cpu_chain, nb); | |
| 86 | + mutex_unlock(&cpu_add_remove_lock); | |
| 81 | 87 | } |
| 82 | 88 | EXPORT_SYMBOL(unregister_cpu_notifier); |
| 83 | 89 | |
| @@ -126,7 +132,7 @@ static int _cpu_down(unsigned int cpu) · 42 unmodified lines | ||
| 126 | 132 | if (!cpu_online(cpu)) |
| 127 | 133 | return -EINVAL; |
| 128 | 134 | |
| 129 | − err = blocking_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE, | |
| 135 | + err = raw_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE, | |
| 130 | 136 | (void *)(long)cpu); |
| 131 | 137 | if (err == NOTIFY_BAD) { |
| 132 | 138 | printk("%s: attempt to take down CPU %u failed\n", |
| @@ -146,7 +152,7 @@ static int _cpu_down(unsigned int cpu) · 13 unmodified lines | ||
| 146 | 152 | |
| 147 | 153 | if (IS_ERR(p)) { |
| 148 | 154 | /* CPU didn't die: tell everyone. Can't complain. */ |
| 149 | − if (blocking_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED, | |
| 155 | + if (raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED, | |
| 150 | 156 | (void *)(long)cpu) == NOTIFY_BAD) |
| 151 | 157 | BUG(); |
| 152 | 158 | |
| @@ -169,7 +175,7 @@ static int _cpu_down(unsigned int cpu) · 16 unmodified lines | ||
| 169 | 175 | put_cpu(); |
| 170 | 176 | |
| 171 | 177 | /* CPU is completely dead: tell everyone. Too late to complain. */ |
| 172 | − if (blocking_notifier_call_chain(&cpu_chain, CPU_DEAD, | |
| 178 | + if (raw_notifier_call_chain(&cpu_chain, CPU_DEAD, | |
| 173 | 179 | (void *)(long)cpu) == NOTIFY_BAD) |
| 174 | 180 | BUG(); |
| 175 | 181 | |
| @@ -206,7 +212,7 @@ static int __devinit _cpu_up(unsigned int cpu) · 30 unmodified lines | ||
| 206 | 212 | if (cpu_online(cpu) || !cpu_present(cpu)) |
| 207 | 213 | return -EINVAL; |
| 208 | 214 | |
| 209 | − ret = blocking_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu); | |
| 215 | + ret = raw_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu); | |
| 210 | 216 | if (ret == NOTIFY_BAD) { |
| 211 | 217 | printk("%s: attempt to bring up CPU %u failed\n", |
| 212 | 218 | __FUNCTION__, cpu); |
| @@ -223,11 +229,11 @@ static int __devinit _cpu_up(unsigned int cpu) · 10 unmodified lines | ||
| 223 | 229 | BUG_ON(!cpu_online(cpu)); |
| 224 | 230 | |
| 225 | 231 | /* Now call notifier in preparation. */ |
| 226 | − blocking_notifier_call_chain(&cpu_chain, CPU_ONLINE, hcpu); | |
| 232 | + raw_notifier_call_chain(&cpu_chain, CPU_ONLINE, hcpu); | |
| 227 | 233 | |
| 228 | 234 | out_notify: |
| 229 | 235 | if (ret != 0) |
| 230 | − blocking_notifier_call_chain(&cpu_chain, | |
| 236 | + raw_notifier_call_chain(&cpu_chain, | |
| 231 | 237 | CPU_UP_CANCELED, hcpu); |
| 232 | 238 | |
| 233 | 239 | return ret; |