[PATCH AUTOSEL 5.9 016/147] um: change sigio_spinlock to a mutex

Sasha Levin
2020-10-26T23:49:59Z

From: Johannes Berg <johannes.berg@intel.com>

[ Upstream commit f2d05059e15af3f70502074f4e3a504530af504a ]

Lockdep complains at boot:

=============================
[ BUG: Invalid wait context ]
5.7.0-05093-g46d91ecd597b #98 Not tainted
-----------------------------
swapper/1 is trying to lock:
0000000060931b98 (&desc[i].request_mutex){+.+.}-{3:3}, at: __setup_irq+0x11d/0x623
other info that might help us debug this:
context-{4:4}
1 lock held by swapper/1:
#0: 000000006074fed8 (sigio_spinlock){+.+.}-{2:2}, at: sigio_lock+0x1a/0x1c
stack backtrace:
CPU: 0 PID: 1 Comm: swapper Not tainted 5.7.0-05093-g46d91ecd597b #98
Stack:
7fa4fab0 6028dfd1 0000002a 6008bea5
7fa50700 7fa50040 7fa4fac0 6028e016
7fa4fb50 6007f6da 60959c18 00000000
Call Trace:
[<60023a0e>] show_stack+0x13b/0x155
[<6028e016>] dump_stack+0x2a/0x2c
[<6007f6da>] __lock_acquire+0x515/0x15f2
[<6007eb50>] lock_acquire+0x245/0x273
[<6050d9f1>] __mutex_lock+0xbd/0x325
[<6050dc76>] mutex_lock_nested+0x1d/0x1f
[<6008e27e>] __setup_irq+0x11d/0x623
[<6008e8ed>] request_threaded_irq+0x169/0x1a6
[<60021eb0>] um_request_irq+0x1ee/0x24b
[<600234ee>] write_sigio_irq+0x3b/0x76
[<600383ca>] sigio_broken+0x146/0x2e4
[<60020bd8>] do_one_initcall+0xde/0x281

Because we hold sigio_spinlock and then get into requesting
an interrupt with a mutex.

Change the spinlock to a mutex to avoid that.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/um/kernel/sigio.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/um/kernel/sigio.c b/arch/um/kernel/sigio.c
index 10c99e058fcae..d1cffc2a7f212 100644
--- a/arch/um/kernel/sigio.c
+++ b/arch/um/kernel/sigio.c
@@ -35,14 +35,14 @@ int write_sigio_irq(int fd)
}

/* These are called from os-Linux/sigio.c to protect its pollfds arrays. */
-static DEFINE_SPINLOCK(sigio_spinlock);
+static DEFINE_MUTEX(sigio_mutex);

void sigio_lock(void)
{
- spin_lock(&sigio_spinlock);
+ mutex_lock(&sigio_mutex);
}

void sigio_unlock(void)
{
- spin_unlock(&sigio_spinlock);
+ mutex_unlock(&sigio_mutex);
}
--
2.25.1