7a61432dc8
Possible recursive locking is detected by lockdep when SMC
falls back to TCP. The corresponding warnings are as follows:
============================================
WARNING: possible recursive locking detected
5.16.0-rc1+ #18 Tainted: G E
--------------------------------------------
wrk/1391 is trying to acquire lock:
ffff975246c8e7d8 (&ei->socket.wq.wait){..-.}-{3:3}, at: smc_switch_to_fallback+0x109/0x250 [smc]
but task is already holding lock:
ffff975246c8f918 (&ei->socket.wq.wait){..-.}-{3:3}, at: smc_switch_to_fallback+0xfe/0x250 [smc]
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(&ei->socket.wq.wait);
lock(&ei->socket.wq.wait);
*** DEADLOCK ***
May be due to missing lock nesting notation
2 locks held by wrk/1391:
#0: ffff975246040130 (sk_lock-AF_SMC){+.+.}-{0:0}, at: smc_connect+0x43/0x150 [smc]
#1: ffff975246c8f918 (&ei->socket.wq.wait){..-.}-{3:3}, at: smc_switch_to_fallback+0xfe/0x250 [smc]
stack backtrace:
Call Trace:
<TASK>
dump_stack_lvl+0x56/0x7b
__lock_acquire+0x951/0x11f0
lock_acquire+0x27a/0x320
? smc_switch_to_fallback+0x109/0x250 [smc]
? smc_switch_to_fallback+0xfe/0x250 [smc]
_raw_spin_lock_irq+0x3b/0x80
? smc_switch_to_fallback+0x109/0x250 [smc]
smc_switch_to_fallback+0x109/0x250 [smc]
smc_connect_fallback+0xe/0x30 [smc]
__smc_connect+0xcf/0x1090 [smc]
? mark_held_locks+0x61/0x80
? __local_bh_enable_ip+0x77/0xe0
? lockdep_hardirqs_on+0xbf/0x130
? smc_connect+0x12a/0x150 [smc]
smc_connect+0x12a/0x150 [smc]
__sys_connect+0x8a/0xc0
? syscall_enter_from_user_mode+0x20/0x70
__x64_sys_connect+0x16/0x20
do_syscall_64+0x34/0x90
entry_SYSCALL_64_after_hwframe+0x44/0xae
The nested locking in smc_switch_to_fallback() is considered to
possibly cause a deadlock because smc_wait->lock and clc_wait->lock
are the same type of lock. But actually it is safe so far since
there is no other place trying to obtain smc_wait->lock when
clc_wait->lock is held. So the patch replaces spin_lock() with
spin_lock_nested() to avoid false report by lockdep.
Link: https://lkml.org/lkml/2021/11/19/962
Fixes:
|
||
|---|---|---|
| Documentation | ||
| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
README
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.