Date: Wed, 05 Dec 2012 19:55:23 +0400 From: Alexandr Matveev <timon@timon.net.nz> To: freebsd-hackers@freebsd.org Subject: sleepq problem Message-ID: <50BF6E6B.2070203@timon.net.nz>
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Hello,
I'm writing a storage controller driver for 9.0-RELEASE-p4 and i'm using
sleepq at initialization to sleep until command is processed by controller:
struct command {
<...>
uint8_t done;
};
void send_command_and_wait(struct command *cmd)
{
command->done = 0;
send_command(cmd);
for (;;) {
sleepq_lock(&command->done);
if (command->done)
break;
sleepq_add(&command->done, NULL, "wait for completion",
SLEEPQ_SLEEP, 0);
sleepq_wait(&command->done, 0);
}
sleepq_release(&command->done);
}
Interrupt handler calls special function when command is processed:
void command_finish(struct command *cmd)
{
sleepq_lock(&command->done);
command->done = 1;
sleepq_signal(&command->done, SLEEPQ_SLEEP, 0, 0);
sleepq_release(&command->done);
}
This code panics very often with following messages:
Sleeping thread (tid 100248, pid 1859) owns a non-sleepable lock
sched_switch() at sched_switch+0xf1
mi_switch() at mi_switch+0x170
sleepq_wait() at sleepq_wait+0x44
send_command_and_wait() at send_command_with_retry+0x77
<...>
panic: sleeping thread
cpuid = 1
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2a
kdb_backtrace() at kdb_backtrace+0x37
panic() at panic+0x187
propagate_priority() at propagate_priority+0x161
turnstile_wait() at turnstile_wait+0x1b8
_mtx_lock_sleep() at _mtx_lock_sleep+0xb0
_mtx_lock_flags() at _mtx_lock_flags+0x96
softclock() at softclock+0x25e
intr_event_execute_handlers() at intr_event_execute_handlers+0x66
ithread_loop() at ithread_loop+0x96
fork_exit() at fork_exit+0x11d
fork_trampoline() at fork_trampoline+0xe
--- trap 0, rip = 0, rsp = 0xffffff80002fad00, rbp = 0 ---
Where tid 100248 is my driver thread which is sleeping & waiting for command
completion:
db> show thread 100248
Thread 100243 at 0xfffffe0146aa98c0:
proc (pid 1859): 0xfffffe02a6815488
name: kldload
stack: 0xffffff8464bf2000-0xffffff8464bf5fff
flags: 0x4 pflags: 0
state: INHIBITED: {SLEEPING}
wmesg: wait for completion wchan: 0xffffff8464c1e244
priority: 127
container lock: sleepq chain (0xffffffff81101af8)
But I can't understand what goes wrong. Sleepq chain lock is owned by
the other thread:
db> show lock 0xffffffff81101af8
class: spin mutex
name: sleepq chain
flags: {SPIN, RECURSE}
state: {OWNED}
owner: 0xfffffe0008377000 (tid 100019, pid 12, "swi4: clock")
Unfortunately, I can't find any examples of using sleepq in drivers.
What am I missing or don't understand?
--
Alexandr Matveev
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