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A kernel hang can be observed when running setserial in a loop on a kernel
with force threaded interrupts. The sequence of events is:
setserial
open("/dev/ttyXXX")
request_irq()
do_stuff()
-> serial interrupt
-> wake(irq_thread)
desc->threads_active++;
close()
free_irq()
kthread_stop(irq_thread)
synchronize_irq() <- hangs because desc->threads_active != 0
The thread is created in request_irq() and woken up, but does not get on a
CPU to reach the actual thread function, which would handle the pending
wake-up. kthread_stop() sets the should stop condition which makes the
thread immediately exit, which in turn leaves the stale threads_active
count around.
This problem was introduced with commit
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|---|---|---|
| .. | ||
| affinity.c | ||
| autoprobe.c | ||
| chip.c | ||
| cpuhotplug.c | ||
| debug.h | ||
| debugfs.c | ||
| devres.c | ||
| dummychip.c | ||
| generic-chip.c | ||
| handle.c | ||
| internals.h | ||
| ipi.c | ||
| irq_sim.c | ||
| irqdesc.c | ||
| irqdomain.c | ||
| Kconfig | ||
| Makefile | ||
| manage.c | ||
| matrix.c | ||
| migration.c | ||
| msi.c | ||
| pm.c | ||
| proc.c | ||
| resend.c | ||
| settings.h | ||
| spurious.c | ||
| timings.c | ||