From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
stable@vger.kernel.org, Douglas Anderson <dianders@chromium.org>,
Daniel Thompson <daniel.thompson@linaro.org>,
Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.4 18/65] kgdb: Avoid suspicious RCU usage warning
Date: Tue, 7 Jul 2020 17:16:57 +0200 [thread overview]
Message-ID: <20200707145753.341011958@linuxfoundation.org> (raw)
In-Reply-To: <20200707145752.417212219@linuxfoundation.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 7d54c7c280544..2222f3225e53d 100644
--- a/kernel/debug/debug_core.c
+++ b/kernel/debug/debug_core.c
@@ -546,6 +546,7 @@ 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.
@@ -602,6 +603,7 @@ return_normal:
atomic_dec(&slaves_in_kgdb);
dbg_touch_watchdogs();
local_irq_restore(flags);
+ rcu_read_unlock();
return 0;
}
cpu_relax();
@@ -620,6 +622,7 @@ return_normal:
raw_spin_unlock(&dbg_master_lock);
dbg_touch_watchdogs();
local_irq_restore(flags);
+ rcu_read_unlock();
goto acquirelock;
}
@@ -743,6 +746,7 @@ kgdb_restore:
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:[~2020-07-07 15:20 UTC|newest]
Thread overview: 78+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-07 15:16 [PATCH 5.4 00/65] 5.4.51-rc1 review Greg Kroah-Hartman
2020-07-07 15:16 ` [PATCH 5.4 01/65] io_uring: make sure async workqueue is canceled on exit Greg Kroah-Hartman
2020-07-07 15:16 ` [PATCH 5.4 02/65] mm: fix swap cache node allocation mask Greg Kroah-Hartman
2020-07-07 15:16 ` [PATCH 5.4 03/65] EDAC/amd64: Read back the scrub rate PCI register on F15h Greg Kroah-Hartman
2020-07-07 15:16 ` [PATCH 5.4 04/65] usbnet: smsc95xx: Fix use-after-free after removal Greg Kroah-Hartman
2020-07-07 15:16 ` [PATCH 5.4 05/65] sched/debug: Make sd->flags sysctl read-only Greg Kroah-Hartman
2020-07-07 15:16 ` [PATCH 5.4 06/65] mm/slub.c: fix corrupted freechain in deactivate_slab() Greg Kroah-Hartman
2020-07-07 15:16 ` [PATCH 5.4 07/65] mm/slub: fix stack overruns with SLUB_STATS Greg Kroah-Hartman
2020-07-07 15:16 ` [PATCH 5.4 08/65] rxrpc: Fix race between incoming ACK parser and retransmitter Greg Kroah-Hartman
2020-07-07 15:16 ` [PATCH 5.4 09/65] usb: usbtest: fix missing kfree(dev->buf) in usbtest_disconnect Greg Kroah-Hartman
2020-07-07 15:16 ` [PATCH 5.4 10/65] tools lib traceevent: Add append() function helper for appending strings Greg Kroah-Hartman
2020-07-07 15:16 ` [PATCH 5.4 11/65] tools lib traceevent: Handle __attribute__((user)) in field names Greg Kroah-Hartman
2020-07-07 15:16 ` [PATCH 5.4 12/65] s390/debug: avoid kernel warning on too large number of pages Greg Kroah-Hartman
2020-07-07 15:16 ` [PATCH 5.4 13/65] nvme-multipath: set bdi capabilities once Greg Kroah-Hartman
2020-07-07 15:16 ` [PATCH 5.4 14/65] nvme: fix possible deadlock when I/O is blocked Greg Kroah-Hartman
2020-07-07 15:16 ` [PATCH 5.4 15/65] nvme-multipath: fix deadlock between ana_work and scan_work Greg Kroah-Hartman
2020-07-07 15:16 ` [PATCH 5.4 16/65] nvme-multipath: fix deadlock due to head->lock Greg Kroah-Hartman
2020-07-07 15:16 ` [PATCH 5.4 17/65] nvme-multipath: fix bogus request queue reference put Greg Kroah-Hartman
2020-07-07 15:16 ` Greg Kroah-Hartman [this message]
2020-07-07 15:16 ` [PATCH 5.4 19/65] selftests: tpm: Use /bin/sh instead of /bin/bash Greg Kroah-Hartman
2020-07-07 15:16 ` [PATCH 5.4 20/65] tpm: Fix TIS locality timeout problems Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 21/65] crypto: af_alg - fix use-after-free in af_alg_accept() due to bh_lock_sock() Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 22/65] drm/msm/dpu: fix error return code in dpu_encoder_init Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 23/65] rxrpc: Fix afs large storage transmission performance drop Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 24/65] RDMA/counter: Query a counter before release Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 25/65] cxgb4: use unaligned conversion for fetching timestamp Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 26/65] cxgb4: parse TC-U32 key values and masks natively Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 27/65] cxgb4: fix endian conversions for L4 ports in filters Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 28/65] cxgb4: use correct type for all-mask IP address comparison Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 29/65] cxgb4: fix SGE queue dump destination buffer context Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 30/65] hwmon: (max6697) Make sure the OVERT mask is set correctly Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 31/65] hwmon: (acpi_power_meter) Fix potential memory leak in acpi_power_meter_add() Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 32/65] thermal/drivers/mediatek: Fix bank number settings on mt8183 Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 33/65] thermal/drivers/rcar_gen3: Fix undefined temperature if negative Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 34/65] kthread: save thread function Greg Kroah-Hartman
2020-07-07 15:31 ` J. Bruce Fields
2020-07-07 15:17 ` [PATCH 5.4 35/65] nfsd: clients dont need to break their own delegations Greg Kroah-Hartman
2020-07-07 15:31 ` J. Bruce Fields
2020-07-07 17:20 ` Sasha Levin
2020-07-07 17:29 ` Sasha Levin
2020-07-07 17:31 ` J. Bruce Fields
2020-07-07 15:17 ` [PATCH 5.4 36/65] nfsd4: fix nfsdfs reference count loop Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 37/65] nfsd: fix nfsdfs inode reference count leak Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 38/65] drm: sun4i: hdmi: Remove extra HPD polling Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 39/65] virtio-blk: free vblk-vqs in error path of virtblk_probe() Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 40/65] SMB3: Honor posix flag for multiuser mounts Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 41/65] nvme: fix identify error status silent ignore Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 42/65] nvme: fix a crash in nvme_mpath_add_disk Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 43/65] samples/vfs: avoid warning in statx override Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 44/65] i2c: algo-pca: Add 0x78 as SCL stuck low status for PCA9665 Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 45/65] i2c: mlxcpld: check correct size of maximum RECV_LEN packet Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 46/65] spi: spi-fsl-dspi: Fix external abort on interrupt in resume or exit paths Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 47/65] nfsd: apply umask on fs without ACL support Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 48/65] Revert "ALSA: usb-audio: Improve frames size computation" Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 49/65] SMB3: Honor seal flag for multiuser mounts Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 50/65] SMB3: Honor persistent/resilient handle flags " Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 51/65] SMB3: Honor lease disabling " Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 52/65] SMB3: Honor handletimeout flag " Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 53/65] cifs: Fix the target file was deleted when rename failed Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 54/65] MIPS: lantiq: xway: sysctrl: fix the GPHY clock alias names Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 55/65] MIPS: Add missing EHB in mtc0 -> mfc0 sequence for DSPen Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 56/65] drm/amd/display: Only revalidate bandwidth on medium and fast updates Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 57/65] drm/amdgpu: use %u rather than %d for sclk/mclk Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 58/65] drm/amdgpu/atomfirmware: fix vram_info fetching for renoir Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 59/65] dma-buf: Move dma_buf_release() from fops to dentry_ops Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 60/65] irqchip/gic: Atomically update affinity Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 61/65] mm, compaction: fully assume capture is not NULL in compact_zone_order() Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 62/65] mm, compaction: make capture control handling safe wrt interrupts Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 63/65] x86/resctrl: Fix memory bandwidth counter width for AMD Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 64/65] dm zoned: assign max_io_len correctly Greg Kroah-Hartman
2020-07-07 15:17 ` [PATCH 5.4 65/65] efi: Make it possible to disable efivar_ssdt entirely Greg Kroah-Hartman
2020-07-08 5:30 ` [PATCH 5.4 00/65] 5.4.51-rc1 review Naresh Kamboju
2020-07-08 8:41 ` Jon Hunter
2020-07-08 15:15 ` Greg Kroah-Hartman
2020-07-08 16:58 ` Jon Hunter
2020-07-09 9:30 ` Greg Kroah-Hartman
2020-07-08 15:00 ` Shuah Khan
2020-07-08 17:53 ` Guenter Roeck
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