From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
stable@vger.kernel.org, Muchun Song <songmuchun@bytedance.com>,
Petr Mladek <pmladek@suse.com>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Subject: [PATCH 4.9 13/41] printk: fix deadlock when kernel panic
Date: Fri, 5 Mar 2021 13:22:20 +0100 [thread overview]
Message-ID: <20210305120851.935800288@linuxfoundation.org> (raw)
In-Reply-To: <20210305120851.255002428@linuxfoundation.org>
From: Muchun Song <songmuchun@bytedance.com>
commit 8a8109f303e25a27f92c1d8edd67d7cbbc60a4eb upstream.
printk_safe_flush_on_panic() caused the following deadlock on our
server:
CPU0: CPU1:
panic rcu_dump_cpu_stacks
kdump_nmi_shootdown_cpus nmi_trigger_cpumask_backtrace
register_nmi_handler(crash_nmi_callback) printk_safe_flush
__printk_safe_flush
raw_spin_lock_irqsave(&read_lock)
// send NMI to other processors
apic_send_IPI_allbutself(NMI_VECTOR)
// NMI interrupt, dead loop
crash_nmi_callback
printk_safe_flush_on_panic
printk_safe_flush
__printk_safe_flush
// deadlock
raw_spin_lock_irqsave(&read_lock)
DEADLOCK: read_lock is taken on CPU1 and will never get released.
It happens when panic() stops a CPU by NMI while it has been in
the middle of printk_safe_flush().
Handle the lock the same way as logbuf_lock. The printk_safe buffers
are flushed only when both locks can be safely taken. It can avoid
the deadlock _in this particular case_ at expense of losing contents
of printk_safe buffers.
Note: It would actually be safe to re-init the locks when all CPUs were
stopped by NMI. But it would require passing this information
from arch-specific code. It is not worth the complexity.
Especially because logbuf_lock and printk_safe buffers have been
obsoleted by the lockless ring buffer.
Fixes: cf9b1106c81c ("printk/nmi: flush NMI messages on the system panic")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: <stable@vger.kernel.org>
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210210034823.64867-1-songmuchun@bytedance.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
kernel/printk/nmi.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)
--- a/kernel/printk/nmi.c
+++ b/kernel/printk/nmi.c
@@ -52,6 +52,8 @@ struct nmi_seq_buf {
};
static DEFINE_PER_CPU(struct nmi_seq_buf, nmi_print_seq);
+static DEFINE_RAW_SPINLOCK(nmi_read_lock);
+
/*
* Safe printk() for NMI context. It uses a per-CPU buffer to
* store the message. NMIs are not nested, so there is always only
@@ -134,8 +136,6 @@ static void printk_nmi_flush_seq_line(st
*/
static void __printk_nmi_flush(struct irq_work *work)
{
- static raw_spinlock_t read_lock =
- __RAW_SPIN_LOCK_INITIALIZER(read_lock);
struct nmi_seq_buf *s = container_of(work, struct nmi_seq_buf, work);
unsigned long flags;
size_t len, size;
@@ -148,7 +148,7 @@ static void __printk_nmi_flush(struct ir
* different CPUs. This is especially important when printing
* a backtrace.
*/
- raw_spin_lock_irqsave(&read_lock, flags);
+ raw_spin_lock_irqsave(&nmi_read_lock, flags);
i = 0;
more:
@@ -197,7 +197,7 @@ more:
goto more;
out:
- raw_spin_unlock_irqrestore(&read_lock, flags);
+ raw_spin_unlock_irqrestore(&nmi_read_lock, flags);
}
/**
@@ -239,6 +239,14 @@ void printk_nmi_flush_on_panic(void)
raw_spin_lock_init(&logbuf_lock);
}
+ if (in_nmi() && raw_spin_is_locked(&nmi_read_lock)) {
+ if (num_online_cpus() > 1)
+ return;
+
+ debug_locks_off();
+ raw_spin_lock_init(&nmi_read_lock);
+ }
+
printk_nmi_flush();
}
next prev parent reply other threads:[~2021-03-05 12:43 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-05 12:22 [PATCH 4.9 00/41] 4.9.260-rc1 review Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 01/41] futex: Cleanup variable names for futex_top_waiter() Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 02/41] futex: Cleanup refcounting Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 03/41] futex: Pull rt_mutex_futex_unlock() out from under hb->lock Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 04/41] futex: Futex_unlock_pi() determinism Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 05/41] futex: Fix pi_state->owner serialization Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 06/41] futex: Fix more put_pi_state() vs. exit_pi_state_list() races Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 07/41] futex: Dont enable IRQs unconditionally in put_pi_state() Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 08/41] net: usb: qmi_wwan: support ZTE P685M modem Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 09/41] arm: kprobes: Allow to handle reentered kprobe on single-stepping Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 10/41] scripts: use pkg-config to locate libcrypto Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 11/41] scripts: set proper OpenSSL include dir also for sign-file Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 12/41] hugetlb: fix update_and_free_page contig page struct assumption Greg Kroah-Hartman
2021-03-05 12:22 ` Greg Kroah-Hartman [this message]
2021-03-05 12:22 ` [PATCH 4.9 14/41] arm64: Remove redundant mov from LL/SC cmpxchg Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 15/41] arm64: Avoid redundant type conversions in xchg() and cmpxchg() Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 16/41] arm64: cmpxchg: Use "K" instead of "L" for ll/sc immediate constraint Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 17/41] arm64: Use correct ll/sc atomic constraints Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 18/41] JFS: more checks for invalid superblock Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 19/41] xfs: Fix assert failure in xfs_setattr_size() Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 20/41] smackfs: restrict bytes count in smackfs write functions Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 21/41] net: fix up truesize of cloned skb in skb_prepare_for_shift() Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 22/41] mm/hugetlb.c: fix unnecessary address expansion of pmd sharing Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 23/41] staging: fwserial: Fix error handling in fwserial_create Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 24/41] x86/reboot: Add Zotac ZBOX CI327 nano PCI reboot quirk Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 25/41] vt/consolemap: do font sum unsigned Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 26/41] wlcore: Fix command execute failure 19 for wl12xx Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 27/41] pktgen: fix misuse of BUG_ON() in pktgen_thread_worker() Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 28/41] ath10k: fix wmi mgmt tx queue full due to race condition Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 29/41] x86/build: Treat R_386_PLT32 relocation as R_386_PC32 Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 30/41] Bluetooth: Fix null pointer dereference in amp_read_loc_assoc_final_data Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 31/41] staging: most: sound: add sanity check for function argument Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 32/41] media: uvcvideo: Allow entities with no pads Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 33/41] scsi: iscsi: Restrict sessions and handles to admin capabilities Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 34/41] sysfs: Add sysfs_emit and sysfs_emit_at to format sysfs output Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 35/41] scsi: iscsi: Ensure sysfs attributes are limited to PAGE_SIZE Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 36/41] scsi: iscsi: Verify lengths on passthrough PDUs Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 37/41] Xen/gnttab: handle p2m update errors on a per-slot basis Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 38/41] xen-netback: respect gnttab_map_refs()s return value Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 39/41] zsmalloc: account the number of compacted pages correctly Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 40/41] swap: fix swapfile read/write offset Greg Kroah-Hartman
2021-03-05 12:22 ` [PATCH 4.9 41/41] media: v4l: ioctl: Fix memory leak in video_usercopy Greg Kroah-Hartman
2021-03-06 5:16 ` [PATCH 4.9 00/41] 4.9.260-rc1 review Florian Fainelli
2021-03-06 16:29 ` Guenter Roeck
2021-03-06 16:30 ` Guenter Roeck
2021-03-07 2:26 ` Naresh Kamboju
2021-03-12 20:24 ` Florian Fainelli
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