From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Petr Mladek <pmladek@suse.com>, Jan Kara <jack@suse.cz>,
Tejun Heo <tj@kernel.org>, Calvin Owens <calvinowens@fb.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Andy Lutomirski <luto@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Peter Hurley <peter@hurleysoftware.com>,
linux-kernel@vger.kernel.org,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Subject: [PATCHv6 0/7] printk: use printk_safe to handle printk() recursive calls
Date: Wed, 21 Dec 2016 23:35:58 +0900 [thread overview]
Message-ID: <20161221143605.2272-1-sergey.senozhatsky@gmail.com> (raw)
Hello,
This patch set extends a lock-less NMI per-cpu buffers idea to
handle recursive printk() calls. The basic mechanism is pretty much the
same -- at the beginning of a deadlock-prone section we switch to lock-less
printk callback, and return back to a default printk implementation at the
end; the messages are getting flushed to a logbuf buffer from a safer
context.
Deadlock scenarios that printk_safe can handle:
a) printk recursion from logbuf_lock spin_lock section in printk()
printk()
raw_spin_lock(&logbuf_lock);
WARN_ON(1);
raw_spin_unlock(&logbuf_lock);
b) printk from sem->lock spin_lock section
printk()
console_trylock()
down_trylock()
raw_spin_lock_irqsave(&sem->lock, flags);
WARN_ON(1);
raw_spin_unlock_irqrestore(&sem->lock, flags);
c) printk from logbuf_lock spin_lock section in console_unlock()
printk()
console_unlock()
raw_spin_lock(&logbuf_lock);
WARN_ON(1);
raw_spin_unlock(&logbuf_lock);
d) printk from ->pi_lock from semaphore up
printk()
console_unlock()
up()
try_to_wake_up()
raw_spin_lock_irqsave(&p->pi_lock, flags);
WARN_ON(1);
raw_spin_unlock_irqrestore(&p->pi_lock, flags);
e) printk from console_cont_flush() /*and down the call chain */
printk()
console_unlock()
call_console_drivers()
...
WARN_ON(1);
v6:
-- re-based
-- addressed Petr's review (added comments; moved lost accounting to seq buf)
v5:
-- some style clean-ups and renamings (Petr)
-- use deferred printk when flush nmi/safe messages (Petr)
v4:
-- addressed Steven's review points
-- use printk_safe in console_cont_flush()
v3: (review by Petr)
-- renamed to printk_safe
-- !NMI config build fix
-- report lost messages for both printk_sae and printk_nmi
-- dropped recursion reporting patch
-- etc.
v2:
-- fix build error on !NMI configs, reported by Fengguang
-- reworked the series based on Petr's feedback
-- added a new patch to drop zap_locks()
Sergey Senozhatsky (7):
printk: use vprintk_func in vprintk()
printk: rename nmi.c and exported api
printk: introduce per-cpu safe_print seq buffer
printk: always use deferred printk when flush printk_safe lines
printk: report lost messages in printk safe/nmi contexts
printk: use printk_safe buffers in printk
printk: remove zap_locks() function
arch/arm/kernel/smp.c | 4 +-
include/linux/hardirq.h | 4 +-
include/linux/printk.h | 29 +++--
init/Kconfig | 16 +--
init/main.c | 2 +-
kernel/kexec_core.c | 2 +-
kernel/panic.c | 4 +-
kernel/printk/Makefile | 2 +-
kernel/printk/internal.h | 63 +++++-----
kernel/printk/printk.c | 116 +++++-------------
kernel/printk/{nmi.c => printk_safe.c} | 216 +++++++++++++++++++++++----------
lib/nmi_backtrace.c | 2 +-
12 files changed, 245 insertions(+), 215 deletions(-)
rename kernel/printk/{nmi.c => printk_safe.c} (53%)
--
2.11.0
next reply other threads:[~2016-12-21 14:36 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-21 14:35 Sergey Senozhatsky [this message]
2016-12-21 14:35 ` [PATCHv6 1/7] printk: use vprintk_func in vprintk() Sergey Senozhatsky
2016-12-21 14:36 ` [PATCHv6 2/7] printk: rename nmi.c and exported api Sergey Senozhatsky
2016-12-21 19:45 ` Linus Torvalds
2016-12-22 1:17 ` Sergey Senozhatsky
2016-12-21 14:36 ` [PATCHv6 3/7] printk: introduce per-cpu safe_print seq buffer Sergey Senozhatsky
2016-12-22 0:53 ` kbuild test robot
2016-12-22 1:18 ` Sergey Senozhatsky
2016-12-22 16:36 ` Petr Mladek
2016-12-21 14:36 ` [PATCHv6 4/7] printk: always use deferred printk when flush printk_safe lines Sergey Senozhatsky
2016-12-21 14:36 ` [PATCHv6 5/7] printk: report lost messages in printk safe/nmi contexts Sergey Senozhatsky
2016-12-23 10:54 ` Petr Mladek
2016-12-23 15:08 ` Sergey Senozhatsky
2016-12-21 14:36 ` [PATCHv6 6/7] printk: use printk_safe buffers in printk Sergey Senozhatsky
2016-12-22 5:31 ` Sergey Senozhatsky
2016-12-22 17:10 ` Petr Mladek
2016-12-23 1:46 ` Sergey Senozhatsky
2016-12-23 9:53 ` Petr Mladek
2016-12-21 14:36 ` [PATCHv6 7/7] printk: remove zap_locks() function Sergey Senozhatsky
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