From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Douglas Anderson <dianders@chromium.org>,
Daniel Thompson <daniel.thompson@linaro.org>,
Sasha Levin <sashal@kernel.org>,
kgdb-bugreport@lists.sourceforge.net
Subject: [PATCH AUTOSEL 5.7 52/53] kgdb: Avoid suspicious RCU usage warning
Date: Wed, 1 Jul 2020 21:22:01 -0400 [thread overview]
Message-ID: <20200702012202.2700645-52-sashal@kernel.org> (raw)
In-Reply-To: <20200702012202.2700645-1-sashal@kernel.org>
From: Douglas Anderson <dianders@chromium.org>
[ Upstream commit 440ab9e10e2e6e5fd677473ee6f9e3af0f6904d6 ]
At times when I'm using kgdb I see a splat on my console about
suspicious RCU usage. I managed to come up with a case that could
reproduce this that looked like this:
WARNING: suspicious RCU usage
5.7.0-rc4+ #609 Not tainted
-----------------------------
kernel/pid.c:395 find_task_by_pid_ns() needs rcu_read_lock() protection!
other info that might help us debug this:
rcu_scheduler_active = 2, debug_locks = 1
3 locks held by swapper/0/1:
#0: ffffff81b6b8e988 (&dev->mutex){....}-{3:3}, at: __device_attach+0x40/0x13c
#1: ffffffd01109e9e8 (dbg_master_lock){....}-{2:2}, at: kgdb_cpu_enter+0x20c/0x7ac
#2: ffffffd01109ea90 (dbg_slave_lock){....}-{2:2}, at: kgdb_cpu_enter+0x3ec/0x7ac
stack backtrace:
CPU: 7 PID: 1 Comm: swapper/0 Not tainted 5.7.0-rc4+ #609
Hardware name: Google Cheza (rev3+) (DT)
Call trace:
dump_backtrace+0x0/0x1b8
show_stack+0x1c/0x24
dump_stack+0xd4/0x134
lockdep_rcu_suspicious+0xf0/0x100
find_task_by_pid_ns+0x5c/0x80
getthread+0x8c/0xb0
gdb_serial_stub+0x9d4/0xd04
kgdb_cpu_enter+0x284/0x7ac
kgdb_handle_exception+0x174/0x20c
kgdb_brk_fn+0x24/0x30
call_break_hook+0x6c/0x7c
brk_handler+0x20/0x5c
do_debug_exception+0x1c8/0x22c
el1_sync_handler+0x3c/0xe4
el1_sync+0x7c/0x100
rpmh_rsc_probe+0x38/0x420
platform_drv_probe+0x94/0xb4
really_probe+0x134/0x300
driver_probe_device+0x68/0x100
__device_attach_driver+0x90/0xa8
bus_for_each_drv+0x84/0xcc
__device_attach+0xb4/0x13c
device_initial_probe+0x18/0x20
bus_probe_device+0x38/0x98
device_add+0x38c/0x420
If I understand properly we should just be able to blanket kgdb under
one big RCU read lock and the problem should go away. We'll add it to
the beast-of-a-function known as kgdb_cpu_enter().
With this I no longer get any splats and things seem to work fine.
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20200602154729.v2.1.I70e0d4fd46d5ed2aaf0c98a355e8e1b7a5bb7e4e@changeid
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/debug/debug_core.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c
index d47c7d6656cd3..9be6accf8fe3d 100644
--- a/kernel/debug/debug_core.c
+++ b/kernel/debug/debug_core.c
@@ -577,6 +577,7 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs,
arch_kgdb_ops.disable_hw_break(regs);
acquirelock:
+ rcu_read_lock();
/*
* Interrupts will be restored by the 'trap return' code, except when
* single stepping.
@@ -636,6 +637,7 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs,
atomic_dec(&slaves_in_kgdb);
dbg_touch_watchdogs();
local_irq_restore(flags);
+ rcu_read_unlock();
return 0;
}
cpu_relax();
@@ -654,6 +656,7 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs,
raw_spin_unlock(&dbg_master_lock);
dbg_touch_watchdogs();
local_irq_restore(flags);
+ rcu_read_unlock();
goto acquirelock;
}
@@ -777,6 +780,7 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs,
raw_spin_unlock(&dbg_master_lock);
dbg_touch_watchdogs();
local_irq_restore(flags);
+ rcu_read_unlock();
return kgdb_info[cpu].ret_state;
}
--
2.25.1
next prev parent reply other threads:[~2020-07-02 1:24 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-02 1:21 [PATCH AUTOSEL 5.7 01/53] soc: ti: omap-prm: use atomic iopoll instead of sleeping one Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 02/53] regmap: fix alignment issue Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 03/53] perf/x86/rapl: Move RAPL support to common x86 code Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 04/53] perf/x86/rapl: Fix RAPL config variable bug Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 05/53] ARM: dts: omap4-droid4: Fix spi configuration and increase rate Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 06/53] drm/ttm: Fix dma_fence refcnt leak in ttm_bo_vm_fault_reserved Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 07/53] drm/ttm: Fix dma_fence refcnt leak when adding move fence Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 08/53] gpu: host1x: Clean up debugfs in error handling path Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 09/53] drm/tegra: hub: Do not enable orphaned window group Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 10/53] gpu: host1x: Detach driver on unregister Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 11/53] btrfs: use kfree() in btrfs_ioctl_get_subvol_info() Sasha Levin
2020-07-02 8:25 ` David Sterba
2020-07-09 22:28 ` Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 12/53] staging: wfx: fix coherency of hif_scan() prototype Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 13/53] drm: mcde: Fix display initialization problem Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 14/53] ASoC: SOF: Intel: add PCI ID for CometLake-S Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 15/53] ASoC: SOF: Intel: add PCI IDs for ICL-H and TGL-H Sasha Levin
2020-07-02 11:18 ` Mark Brown
2020-07-02 15:42 ` Pierre-Louis Bossart
2020-07-02 16:05 ` Mark Brown
2020-07-09 22:29 ` Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 16/53] ASoC: hdac_hda: fix memleak with regmap not freed on remove Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 17/53] net: usb: ax88179_178a: fix packet alignment padding Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 18/53] ALSA: hda: Intel: add missing PCI IDs for ICL-H, TGL-H and EKL Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 19/53] usb: usbtest: fix missing kfree(dev->buf) in usbtest_disconnect Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 20/53] spi: spidev: fix a race between spidev_release and spidev_remove Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 21/53] spi: spidev: fix a potential use-after-free in spidev_release() Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 22/53] net: ethernet: mvneta: Fix Serdes configuration for SoCs without comphy Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 23/53] net: ethernet: mvneta: Add 2500BaseX support " Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 24/53] tg3: driver sleeps indefinitely when EEH errors exceed eeh_max_freezes Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 25/53] ixgbe: protect ring accesses with READ- and WRITE_ONCE Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 26/53] i40e: " Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 27/53] ice: protect ring accesses with WRITE_ONCE Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 28/53] ibmvnic: continue to init in CRQ reset returns H_CLOSED Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 29/53] powerpc/kvm/book3s64: Fix kernel crash with nested kvm & DEBUG_VIRTUAL Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 30/53] xprtrdma: Prevent dereferencing r_xprt->rx_ep after it is freed Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 31/53] usbnet: smsc95xx: Fix use-after-free after removal Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 32/53] iommu/vt-d: Don't apply gfx quirks to untrusted devices Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 33/53] drm: panel-orientation-quirks: Add quirk for Asus T101HA panel Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 34/53] drm: panel-orientation-quirks: Use generic orientation-data for Acer S1003 Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 35/53] s390/kasan: fix early pgm check handler execution Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 36/53] s390/debug: avoid kernel warning on too large number of pages Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 37/53] cifs: Fix double add page to memcg when cifs_readpages Sasha Levin
2020-07-02 16:08 ` Pavel Shilovsky
2020-07-09 23:49 ` Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 38/53] drm/sun4i: mixer: Call of_dma_configure if there's an IOMMU Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 39/53] io_uring: fix io_sq_thread no schedule when busy Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 40/53] cifs: update ctime and mtime during truncate Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 41/53] ARM: imx6: add missing put_device() call in imx6q_suspend_init() Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 42/53] scsi: qla2xxx: Fix MPI failure AEN (8200) handling Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 43/53] scsi: mptscsih: Fix read sense data size Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 44/53] usb: dwc3: pci: Fix reference count leak in dwc3_pci_resume_work Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 45/53] arm64: kpti: Add KRYO{3, 4}XX silver CPU cores to kpti safelist Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 46/53] block: release bip in a right way in error path Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 47/53] nvme-rdma: assign completion vector correctly Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 48/53] x86/entry: Increase entry_stack size to a full page Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 49/53] io_uring: fix current->mm NULL dereference on exit Sasha Levin
2020-07-02 1:21 ` [PATCH AUTOSEL 5.7 50/53] arm64: Add KRYO{3,4}XX silver CPU cores to SSB safelist Sasha Levin
2020-07-02 1:22 ` [PATCH AUTOSEL 5.7 51/53] nfs: Fix memory leak of export_path Sasha Levin
2020-07-02 1:22 ` Sasha Levin [this message]
2020-07-02 1:22 ` [PATCH AUTOSEL 5.7 53/53] sched/core: Check cpus_mask, not cpus_ptr in __set_cpus_allowed_ptr(), to fix mask corruption Sasha Levin
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