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The writer acquires dev_base_lock with disabled bottom halves. The reader can acquire dev_base_lock without disabling bottom halves because there is no writer in softirq context. On PREEMPT_RT the softirqs are preemptible and local_bh_disable() acts as a lock to ensure that resources, that are protected by disabling bottom halves, remain protected. This leads to a circular locking dependency if the lock acquired with disabled bottom halves (as in write_lock_bh()) and somewhere else with enabled bottom halves (as by read_lock() in netstat_show()) followed by disabling bottom halves (cxgb_get_stats() -> t4_wr_mbox_meat_timeout() -> spin_lock_bh()). This is the reverse locking order. All read_lock() invocation are from sysfs callback which are not invoked from softirq context. Therefore there is no need to disable bottom halves while acquiring a write lock. Acquire the write lock of dev_base_lock without disabling bottom halves. Reported-by: Pei Zhang <pezhang@redhat.com> Reported-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: David S. Miller <davem@davemloft.net> |
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| .. | ||
| hsr_debugfs.c | ||
| hsr_device.c | ||
| hsr_device.h | ||
| hsr_forward.c | ||
| hsr_forward.h | ||
| hsr_framereg.c | ||
| hsr_framereg.h | ||
| hsr_main.c | ||
| hsr_main.h | ||
| hsr_netlink.c | ||
| hsr_netlink.h | ||
| hsr_slave.c | ||
| hsr_slave.h | ||
| Kconfig | ||
| Makefile | ||