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[ Upstream commit c14376de3a1befa70d9811ca2872d47367b48767 ]
wake_klogd is a local variable in console_unlock(). The information
is lost when the console_lock owner using the busy wait added by
the commit dbdda842fe96f8932 ("printk: Add console owner and waiter
logic to load balance console writes"). The following race is
possible:
CPU0 CPU1
console_unlock()
for (;;)
/* calling console for last message */
printk()
log_store()
log_next_seq++;
/* see new message */
if (seen_seq != log_next_seq) {
wake_klogd = true;
seen_seq = log_next_seq;
}
console_lock_spinning_enable();
if (console_trylock_spinning())
/* spinning */
if (console_lock_spinning_disable_and_check()) {
printk_safe_exit_irqrestore(flags);
return;
console_unlock()
if (seen_seq != log_next_seq) {
/* already seen */
/* nothing to do */
Result: Nobody would wakeup klogd.
One solution would be to make a global variable from wake_klogd.
But then we would need to manipulate it under a lock or so.
This patch wakes klogd also when console_lock is passed to the
spinning waiter. It looks like the right way to go. Also userspace
should have a chance to see and store any "flood" of messages.
Note that the very late klogd wake up was a historic solution.
It made sense on single CPU systems or when sys_syslog() operations
were synchronized using the big kernel lock like in v2.1.113.
But it is questionable these days.
Fixes: dbdda842fe96f8932 ("printk: Add console owner and waiter logic to load balance console writes")
Link: http://lkml.kernel.org/r/20180226155734.dzwg3aovqnwtvkoy@pathway.suse.cz
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org
Cc: Tejun Heo <tj@kernel.org>
Suggested-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
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[ Upstream commit fd5f7cde1b85d4c8e09ca46ce948e008a2377f64 ]
This patch, basically, reverts commit 6b97a20d3a79 ("printk:
set may_schedule for some of console_trylock() callers").
That commit was a mistake, it introduced a big dependency
on the scheduler, by enabling preemption under console_sem
in printk()->console_unlock() path, which is rather too
critical. The patch did not significantly reduce the
possibilities of printk() lockups, but made it possible to
stall printk(), as has been reported by Tetsuo Handa [1].
Another issues is that preemption under console_sem also
messes up with Steven Rostedt's hand off scheme, by making
it possible to sleep with console_sem both in console_unlock()
and in vprintk_emit(), after acquiring the console_sem
ownership (anywhere between printk_safe_exit_irqrestore() in
console_trylock_spinning() and printk_safe_enter_irqsave()
in console_unlock()). This makes hand off less likely and,
at the same time, may result in a significant amount of
pending logbuf messages. Preempted console_sem owner makes
it impossible for other CPUs to emit logbuf messages, but
does not make it impossible for other CPUs to append new
messages to the logbuf.
Reinstate the old behavior and make printk() non-preemptible.
Should any printk() lockup reports arrive they must be handled
in a different way.
[1] http://lkml.kernel.org/r/201603022101.CAH73907.OVOOMFHFFtQJSL%20()%20I-love%20!%20SAKURA%20!%20ne%20!%20jp
Fixes: 6b97a20d3a79 ("printk: set may_schedule for some of console_trylock() callers")
Link: http://lkml.kernel.org/r/20180116044716.GE6607@jagdpanzerIV
To: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: akpm@linux-foundation.org
Cc: linux-mm@kvack.org
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
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[ Upstream commit c162d5b4338d72deed61aa65ed0f2f4ba2bbc8ab ]
The commit ("printk: Add console owner and waiter logic to load balance
console writes") made vprintk_emit() and console_unlock() even more
complicated.
This patch extracts the new code into 3 helper functions. They should
help to keep it rather self-contained. It will be easier to use and
maintain.
This patch just shuffles the existing code. It does not change
the functionality.
Link: http://lkml.kernel.org/r/20180112160837.GD24497@linux.suse
Cc: akpm@linux-foundation.org
Cc: linux-mm@kvack.org
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: rostedt@home.goodmis.org
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
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[ Upstream commit dbdda842fe96f8932bae554f0adf463c27c42bc7 ]
This patch implements what I discussed in Kernel Summit. I added
lockdep annotation (hopefully correctly), and it hasn't had any splats
(since I fixed some bugs in the first iterations). It did catch
problems when I had the owner covering too much. But now that the owner
is only set when actively calling the consoles, lockdep has stayed
quiet.
Here's the design again:
I added a "console_owner" which is set to a task that is actively
writing to the consoles. It is *not* the same as the owner of the
console_lock. It is only set when doing the calls to the console
functions. It is protected by a console_owner_lock which is a raw spin
lock.
There is a console_waiter. This is set when there is an active console
owner that is not current, and waiter is not set. This too is protected
by console_owner_lock.
In printk() when it tries to write to the consoles, we have:
if (console_trylock())
console_unlock();
Now I added an else, which will check if there is an active owner, and
no current waiter. If that is the case, then console_waiter is set, and
the task goes into a spin until it is no longer set.
When the active console owner finishes writing the current message to
the consoles, it grabs the console_owner_lock and sees if there is a
waiter, and clears console_owner.
If there is a waiter, then it breaks out of the loop, clears the waiter
flag (because that will release the waiter from its spin), and exits.
Note, it does *not* release the console semaphore. Because it is a
semaphore, there is no owner. Another task may release it. This means
that the waiter is guaranteed to be the new console owner! Which it
becomes.
Then the waiter calls console_unlock() and continues to write to the
consoles.
If another task comes along and does a printk() it too can become the
new waiter, and we wash rinse and repeat!
By Petr Mladek about possible new deadlocks:
The thing is that we move console_sem only to printk() call
that normally calls console_unlock() as well. It means that
the transferred owner should not bring new type of dependencies.
As Steven said somewhere: "If there is a deadlock, it was
there even before."
We could look at it from this side. The possible deadlock would
look like:
CPU0 CPU1
console_unlock()
console_owner = current;
spin_lockA()
printk()
spin = true;
while (...)
call_console_drivers()
spin_lockA()
This would be a deadlock. CPU0 would wait for the lock A.
While CPU1 would own the lockA and would wait for CPU0
to finish calling the console drivers and pass the console_sem
owner.
But if the above is true than the following scenario was
already possible before:
CPU0
spin_lockA()
printk()
console_unlock()
call_console_drivers()
spin_lockA()
By other words, this deadlock was there even before. Such
deadlocks are prevented by using printk_deferred() in
the sections guarded by the lock A.
By Steven Rostedt:
To demonstrate the issue, this module has been shown to lock up a
system with 4 CPUs and a slow console (like a serial console). It is
also able to lock up a 8 CPU system with only a fast (VGA) console, by
passing in "loops=100". The changes in this commit prevent this module
from locking up the system.
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/sched.h>
#include <linux/mutex.h>
#include <linux/workqueue.h>
#include <linux/hrtimer.h>
static bool stop_testing;
static unsigned int loops = 1;
static void preempt_printk_workfn(struct work_struct *work)
{
int i;
while (!READ_ONCE(stop_testing)) {
for (i = 0; i < loops && !READ_ONCE(stop_testing); i++) {
preempt_disable();
pr_emerg("%5d%-75s\n", smp_processor_id(),
" XXX NOPREEMPT");
preempt_enable();
}
msleep(1);
}
}
static struct work_struct __percpu *works;
static void finish(void)
{
int cpu;
WRITE_ONCE(stop_testing, true);
for_each_online_cpu(cpu)
flush_work(per_cpu_ptr(works, cpu));
free_percpu(works);
}
static int __init test_init(void)
{
int cpu;
works = alloc_percpu(struct work_struct);
if (!works)
return -ENOMEM;
/*
* This is just a test module. This will break if you
* do any CPU hot plugging between loading and
* unloading the module.
*/
for_each_online_cpu(cpu) {
struct work_struct *work = per_cpu_ptr(works, cpu);
INIT_WORK(work, &preempt_printk_workfn);
schedule_work_on(cpu, work);
}
return 0;
}
static void __exit test_exit(void)
{
finish();
}
module_param(loops, uint, 0);
module_init(test_init);
module_exit(test_exit);
MODULE_LICENSE("GPL");
Link: http://lkml.kernel.org/r/20180110132418.7080-2-pmladek@suse.com
Cc: akpm@linux-foundation.org
Cc: linux-mm@kvack.org
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
[pmladek@suse.com: Commit message about possible deadlocks]
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
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This reverts commit c9b8d580b3fb0ab65d37c372aef19a318fda3199.
This is just a technical revert to make the printk fix apply cleanly,
this patch will be re-picked in about 3 commits.
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commit fd5f7cde1b85d4c8e09ca46ce948e008a2377f64 upstream.
This patch, basically, reverts commit 6b97a20d3a79 ("printk:
set may_schedule for some of console_trylock() callers").
That commit was a mistake, it introduced a big dependency
on the scheduler, by enabling preemption under console_sem
in printk()->console_unlock() path, which is rather too
critical. The patch did not significantly reduce the
possibilities of printk() lockups, but made it possible to
stall printk(), as has been reported by Tetsuo Handa [1].
Another issues is that preemption under console_sem also
messes up with Steven Rostedt's hand off scheme, by making
it possible to sleep with console_sem both in console_unlock()
and in vprintk_emit(), after acquiring the console_sem
ownership (anywhere between printk_safe_exit_irqrestore() in
console_trylock_spinning() and printk_safe_enter_irqsave()
in console_unlock()). This makes hand off less likely and,
at the same time, may result in a significant amount of
pending logbuf messages. Preempted console_sem owner makes
it impossible for other CPUs to emit logbuf messages, but
does not make it impossible for other CPUs to append new
messages to the logbuf.
Reinstate the old behavior and make printk() non-preemptible.
Should any printk() lockup reports arrive they must be handled
in a different way.
[1] http://lkml.kernel.org/r/201603022101.CAH73907.OVOOMFHFFtQJSL%20()%20I-love%20!%20SAKURA%20!%20ne%20!%20jp
Fixes: 6b97a20d3a79 ("printk: set may_schedule for some of console_trylock() callers")
Link: http://lkml.kernel.org/r/20180116044716.GE6607@jagdpanzerIV
To: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: akpm@linux-foundation.org
Cc: linux-mm@kvack.org
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 277fcdb2cfee38ccdbe07e705dbd4896ba0c9930 upstream.
log_buf_len_setup does not check input argument before passing it to
simple_strtoull. The argument would be a NULL pointer if "log_buf_len",
without its value, is set in command line and thus causes the following
panic.
PANIC: early exception 0xe3 IP 10:ffffffffaaeacd0d error 0 cr2 0x0
[ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 4.19.0-rc4-yocto-standard+ #1
[ 0.000000] RIP: 0010:_parse_integer_fixup_radix+0xd/0x70
...
[ 0.000000] Call Trace:
[ 0.000000] simple_strtoull+0x29/0x70
[ 0.000000] memparse+0x26/0x90
[ 0.000000] log_buf_len_setup+0x17/0x22
[ 0.000000] do_early_param+0x57/0x8e
[ 0.000000] parse_args+0x208/0x320
[ 0.000000] ? rdinit_setup+0x30/0x30
[ 0.000000] parse_early_options+0x29/0x2d
[ 0.000000] ? rdinit_setup+0x30/0x30
[ 0.000000] parse_early_param+0x36/0x4d
[ 0.000000] setup_arch+0x336/0x99e
[ 0.000000] start_kernel+0x6f/0x4ee
[ 0.000000] x86_64_start_reservations+0x24/0x26
[ 0.000000] x86_64_start_kernel+0x6f/0x72
[ 0.000000] secondary_startup_64+0xa4/0xb0
This patch adds a check to prevent the panic.
Link: http://lkml.kernel.org/r/1538239553-81805-1-git-send-email-zhe.he@windriver.com
Cc: stable@vger.kernel.org
Cc: rostedt@goodmis.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: He Zhe <zhe.he@windriver.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit d1c392c9e2a301f38998a353f467f76414e38725 upstream.
I hit the following splat in my tests:
------------[ cut here ]------------
IRQs not enabled as expected
WARNING: CPU: 3 PID: 0 at kernel/time/tick-sched.c:982 tick_nohz_idle_enter+0x44/0x8c
Modules linked in: ip6t_REJECT nf_reject_ipv6 ip6table_filter ip6_tables ipv6
CPU: 3 PID: 0 Comm: swapper/3 Not tainted 4.19.0-rc2-test+ #2
Hardware name: MSI MS-7823/CSM-H87M-G43 (MS-7823), BIOS V1.6 02/22/2014
EIP: tick_nohz_idle_enter+0x44/0x8c
Code: ec 05 00 00 00 75 26 83 b8 c0 05 00 00 00 75 1d 80 3d d0 36 3e c1 00
75 14 68 94 63 12 c1 c6 05 d0 36 3e c1 01 e8 04 ee f8 ff <0f> 0b 58 fa bb a0
e5 66 c1 e8 25 0f 04 00 64 03 1d 28 31 52 c1 8b
EAX: 0000001c EBX: f26e7f8c ECX: 00000006 EDX: 00000007
ESI: f26dd1c0 EDI: 00000000 EBP: f26e7f40 ESP: f26e7f38
DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 EFLAGS: 00010296
CR0: 80050033 CR2: 0813c6b0 CR3: 2f342000 CR4: 001406f0
Call Trace:
do_idle+0x33/0x202
cpu_startup_entry+0x61/0x63
start_secondary+0x18e/0x1ed
startup_32_smp+0x164/0x168
irq event stamp: 18773830
hardirqs last enabled at (18773829): [<c040150c>] trace_hardirqs_on_thunk+0xc/0x10
hardirqs last disabled at (18773830): [<c040151c>] trace_hardirqs_off_thunk+0xc/0x10
softirqs last enabled at (18773824): [<c0ddaa6f>] __do_softirq+0x25f/0x2bf
softirqs last disabled at (18773767): [<c0416bbe>] call_on_stack+0x45/0x4b
---[ end trace b7c64aa79e17954a ]---
After a bit of debugging, I found what was happening. This would trigger
when performing "perf" with a high NMI interrupt rate, while enabling and
disabling function tracer. Ftrace uses breakpoints to convert the nops at
the start of functions to calls to the function trampolines. The breakpoint
traps disable interrupts and this makes calls into lockdep via the
trace_hardirqs_off_thunk in the entry.S code. What happens is the following:
do_idle {
[interrupts enabled]
<interrupt> [interrupts disabled]
TRACE_IRQS_OFF [lockdep says irqs off]
[...]
TRACE_IRQS_IRET
test if pt_regs say return to interrupts enabled [yes]
TRACE_IRQS_ON [lockdep says irqs are on]
<nmi>
nmi_enter() {
printk_nmi_enter() [traced by ftrace]
[ hit ftrace breakpoint ]
<breakpoint exception>
TRACE_IRQS_OFF [lockdep says irqs off]
[...]
TRACE_IRQS_IRET [return from breakpoint]
test if pt_regs say interrupts enabled [no]
[iret back to interrupt]
[iret back to code]
tick_nohz_idle_enter() {
lockdep_assert_irqs_enabled() [lockdep say no!]
Although interrupts are indeed enabled, lockdep thinks it is not, and since
we now do asserts via lockdep, it gives a false warning. The issue here is
that printk_nmi_enter() is called before lockdep_off(), which disables
lockdep (for this reason) in NMIs. By simply not allowing ftrace to see
printk_nmi_enter() (via notrace annotation) we keep lockdep from getting
confused.
Cc: stable@vger.kernel.org
Fixes: 42a0bb3f71383 ("printk/nmi: generic solution for safe printk in NMI")
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 03fc7f9c99c1e7ae2925d459e8487f1a6f199f79 upstream.
The commit 719f6a7040f1bdaf96 ("printk: Use the main logbuf in NMI
when logbuf_lock is available") brought back the possible deadlocks
in printk() and NMI.
The check of logbuf_lock is done only in printk_nmi_enter() to prevent
mixed output. But another CPU might take the lock later, enter NMI, and:
+ Both NMIs might be serialized by yet another lock, for example,
the one in nmi_cpu_backtrace().
+ The other CPU might get stopped in NMI, see smp_send_stop()
in panic().
The only safe solution is to use trylock when storing the message
into the main log-buffer. It might cause reordering when some lines
go to the main lock buffer directly and others are delayed via
the per-CPU buffer. It means that it is not useful in general.
This patch replaces the problematic NMI deferred context with NMI
direct context. It can be used to mark a code that might produce
many messages in NMI and the risk of losing them is more critical
than problems with eventual reordering.
The context is then used when dumping trace buffers on oops. It was
the primary motivation for the original fix. Also the reordering is
even smaller issue there because some traces have their own time stamps.
Finally, nmi_cpu_backtrace() need not longer be serialized because
it will always us the per-CPU buffers again.
Fixes: 719f6a7040f1bdaf96 ("printk: Use the main logbuf in NMI when logbuf_lock is available")
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/20180627142028.11259-1-pmladek@suse.com
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: linux-kernel@vger.kernel.org
Cc: stable@vger.kernel.org
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit a338f84dc196f44b63ba0863d2f34fd9b1613572 upstream.
It is just a preparation step. The patch does not change
the existing behavior.
Link: http://lkml.kernel.org/r/20180627140817.27764-3-pmladek@suse.com
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: linux-kernel@vger.kernel.org
Cc: stable@vger.kernel.org
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit ba552399954dde1b388f7749fecad5c349216981 upstream.
It is just a preparation step. The patch does not change
the existing behavior.
Link: http://lkml.kernel.org/r/20180627140817.27764-2-pmladek@suse.com
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: linux-kernel@vger.kernel.org
Cc: stable@vger.kernel.org
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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[ Upstream commit 554755be08fba31c74f66b82a485e5513205af84 ]
Drop the in_nmi() check from printk_safe_flush_on_panic()
and attempt to re-init (IOW unlock) locked logbuf spinlock
from panic CPU regardless of its context.
Otherwise, theoretically, we can deadlock on logbuf trying to flush
per-CPU buffers:
a) Panic CPU is running in non-NMI context
b) Panic CPU sends out shutdown IPI via reboot vector
c) Panic CPU fails to stop all remote CPUs
d) Panic CPU sends out shutdown IPI via NMI vector
One of the CPUs that we bring down via NMI vector can hold
logbuf spin lock (theoretically).
Link: http://lkml.kernel.org/r/20180530070350.10131-1-sergey.senozhatsky@gmail.com
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 988a35f8da1dec5a8cd2788054d1e717be61bf25 upstream.
I noticed that there is a possibility that printk_safe_log_store() causes
kernel oops because "args" parameter is passed to vsnprintf() again when
atomic_cmpxchg() detected that we raced. Fix this by using va_copy().
Link: http://lkml.kernel.org/r/201805112002.GIF21216.OFVHFOMLJtQFSO@I-love.SAKURA.ne.jp
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: dvyukov@google.com
Cc: syzkaller@googlegroups.com
Cc: fengguang.wu@intel.com
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Fixes: 42a0bb3f71383b45 ("printk/nmi: generic solution for safe printk in NMI")
Cc: 4.7+ <stable@vger.kernel.org> # v4.7+
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.
By default all files without license information are under the default
license of the kernel, which is GPL version 2.
Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier. The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.
This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.
How this work was done:
Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
- file had no licensing information it it.
- file was a */uapi/* one with no licensing information in it,
- file was a */uapi/* one with existing licensing information,
Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.
The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne. Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.
The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed. Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.
Criteria used to select files for SPDX license identifier tagging was:
- Files considered eligible had to be source code files.
- Make and config files were included as candidates if they contained >5
lines of source
- File already had some variant of a license header in it (even if <5
lines).
All documentation files were explicitly excluded.
The following heuristics were used to determine which SPDX license
identifiers to apply.
- when both scanners couldn't find any license traces, file was
considered to have no license information in it, and the top level
COPYING file license applied.
For non */uapi/* files that summary was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 11139
and resulted in the first patch in this series.
If that file was a */uapi/* path one, it was "GPL-2.0 WITH
Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 WITH Linux-syscall-note 930
and resulted in the second patch in this series.
- if a file had some form of licensing information in it, and was one
of the */uapi/* ones, it was denoted with the Linux-syscall-note if
any GPL family license was found in the file or had no licensing in
it (per prior point). Results summary:
SPDX license identifier # files
---------------------------------------------------|------
GPL-2.0 WITH Linux-syscall-note 270
GPL-2.0+ WITH Linux-syscall-note 169
((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21
((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17
LGPL-2.1+ WITH Linux-syscall-note 15
GPL-1.0+ WITH Linux-syscall-note 14
((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5
LGPL-2.0+ WITH Linux-syscall-note 4
LGPL-2.1 WITH Linux-syscall-note 3
((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3
((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1
and that resulted in the third patch in this series.
- when the two scanners agreed on the detected license(s), that became
the concluded license(s).
- when there was disagreement between the two scanners (one detected a
license but the other didn't, or they both detected different
licenses) a manual inspection of the file occurred.
- In most cases a manual inspection of the information in the file
resulted in a clear resolution of the license that should apply (and
which scanner probably needed to revisit its heuristics).
- When it was not immediately clear, the license identifier was
confirmed with lawyers working with the Linux Foundation.
- If there was any question as to the appropriate license identifier,
the file was flagged for further research and to be revisited later
in time.
In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.
Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights. The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.
Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.
In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.
Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
- a full scancode scan run, collecting the matched texts, detected
license ids and scores
- reviewing anything where there was a license detected (about 500+
files) to ensure that the applied SPDX license was correct
- reviewing anything where there was no detection but the patch license
was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
SPDX license was correct
This produced a worksheet with 20 files needing minor correction. This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.
These .csv files were then reviewed by Greg. Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected. This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.) Finally Greg ran the script using the .csv files to
generate the patches.
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk
Pull printk updates from Petr Mladek:
- Do not allow use of freed init data and code even when boot consoles
are forced to stay. Also check for the init memory more precisely.
- Some code clean up by starting contributors.
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk:
printk: Clean up do_syslog() error handling
printk/console: Enhance the check for consoles using init memory
printk/console: Always disable boot consoles that use init memory before it is freed
printk: Modify operators of printed_len and text_len
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This reverts commit 68c4a4f8abc60c9440ede9cd123d48b78325f7a3, with
various conflict clean-ups.
The capability check required too much privilege compared to simple DAC
controls. A system builder was forced to have crash handler processes
run with CAP_SYSLOG which would give it the ability to read (and wipe)
the _current_ dmesg, which is much more access than being given access
only to the historical log stored in pstorefs.
With the prior commit to make the root directory 0750, the files are
protected by default but a system builder can now opt to give access
to a specific group (via chgrp on the pstorefs root directory) without
being forced to also give away CAP_SYSLOG.
Suggested-by: Nick Kralevich <nnk@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Petr Mladek <pmladek@suse.cz>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
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The error variable in do_syslog() is preemptively set to the error code
before the error condition is checked, and then set to 0 if the error
condition is not encountered. This is not necessary, as it is likely
simpler to return immediately upon encountering the error condition. A
redundant set of the error variable to 0 is also removed.
This patch has been build-tested on x86_64, but not tested for
functionality.
Link: http://lkml.kernel.org/r/20170730033636.GA935@vostro
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Nikitas Angelinas <nikitas.angelinas@gmail.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
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printk_late_init() is responsible for disabling boot consoles that
use init memory. It checks the address of struct console for this.
But this is not enough. For example, there are several early
consoles that have write() method in the init section and
struct console in the normal section. They are not disabled
and could cause fancy and hard to debug system states.
It is even more complicated by the macros EARLYCON_DECLARE() and
OF_EARLYCON_DECLARE() where various struct members are set at
runtime by the provided setup() function.
I have tried to reproduce this problem and forced the classic uart
early console to stay using keep_bootcon parameter. In particular
I used earlycon=uart,io,0x3f8 keep_bootcon console=ttyS0,115200.
The system did not boot:
[ 1.570496] PM: Image not found (code -22)
[ 1.570496] PM: Image not found (code -22)
[ 1.571886] PM: Hibernation image not present or could not be loaded.
[ 1.571886] PM: Hibernation image not present or could not be loaded.
[ 1.576407] Freeing unused kernel memory: 2528K
[ 1.577244] kernel tried to execute NX-protected page - exploit attempt? (uid: 0)
The double lines are caused by having both early uart console and
ttyS0 console enabled at the same time. The early console stopped
working when the init memory was freed. Fortunately, the invalid
call was caught by the NX-protexted page check and did not cause
any silent fancy problems.
This patch adds a check for many other addresses stored in
struct console. It omits setup() and match() that are used
only when the console is registered. Therefore they have
already been used at this point and there is no reason
to use them again.
Link: http://lkml.kernel.org/r/1500036673-7122-3-git-send-email-pmladek@suse.com
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Matt Redfearn <matt.redfearn@imgtec.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
Cc: "Fabio M. Di Nitto" <fdinitto@redhat.com>
Cc: linux-serial@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
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is freed
Commit 4c30c6f566c0 ("kernel/printk: do not turn off bootconsole in
printk_late_init() if keep_bootcon") added a check on keep_bootcon to
ensure that boot consoles were kept around until the real console is
registered.
This can lead to problems if the boot console data and code are in the
init section, since it can be freed before the boot console is
unregistered.
Commit 81cc26f2bd11 ("printk: only unregister boot consoles when
necessary") fixed this a better way. It allowed to keep boot consoles
that did not use init data. Unfortunately it did not remove the check
of keep_bootcon.
This can lead to crashes and weird panics when the bootconsole is
accessed after free, especially if page poisoning is in use and the
code / data have been overwritten with a poison value.
To prevent this, always free the boot console if it is within the init
section. In addition, print a warning about that the console is removed
prematurely.
Finally there is a new comment how to avoid the warning. It replaced
an explanation that duplicated a more comprehensive function
description few lines above.
Fixes: 4c30c6f566c0 ("kernel/printk: do not turn off bootconsole in printk_late_init() if keep_bootcon")
Link: http://lkml.kernel.org/r/1500036673-7122-2-git-send-email-pmladek@suse.com
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
Cc: "Fabio M. Di Nitto" <fdinitto@redhat.com>
Cc: linux-serial@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Matt Redfearn <matt.redfearn@imgtec.com>
[pmladek@suse.com: print the warning, code and comments clean up]
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
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With commit <ddb9baa82226> ("printk: report lost messages in printk
safe/nmi contexts") and commit <8b1742c9c207> ("printk: remove zap_locks()
function"), it seems we can remove initialization, "=0", of text_len and
directly assign result of log_output to printed_len.
Link: http://lkml.kernel.org/r/1499755255-6258-1-git-send-email-vichy.kuo@gmail.com
Cc: rostedt@goodmis.org
Cc: linux-kernel@vger.kernel.org
Cc: joe@perches.com
Signed-off-by: Pierre Kuo <vichy.kuo@gmail.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
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git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk
Pull printk updates from Petr Mladek:
- Store printk() messages into the main log buffer directly even in NMI
when the lock is available. It is the best effort to print even large
chunk of text. It is handy, for example, when all ftrace messages are
printed during the system panic in NMI.
- Add missing annotations to calm down compiler warnings
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk:
printk: add __printf attributes to internal functions
printk: Use the main logbuf in NMI when logbuf_lock is available
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Conflicts:
kernel/sched/Makefile
Pick up the waitqueue related renames - it didn't get much feedback,
so it appears to be uncontroversial. Famous last words? ;-)
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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When compiling with -Wsuggest-attribute=format, gcc complains that some
functions in kernel/printk/printk_safe.c transmit their argument to
printf-like functions without having a printf attribute. Silence these
warnings by adding relevant __printf attributes.
Link: http://lkml.kernel.org/r/20170524054950.6722-1-nicolas.iooss_linux@m4x.org
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Nicolas Iooss <nicolas.iooss_linux@m4x.org>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
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git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk
Pull printk fix from Petr Mladek:
"This reverts a fix added into 4.12-rc1. It caused the kernel log to be
printed on another console when two consoles of the same type were
defined, e.g. console=ttyS0 console=ttyS1.
This configuration was never supported by kernel itself, but it
started to make sense with systemd. In other words, the commit broke
userspace"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk:
Revert "printk: fix double printing with earlycon"
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This reverts commit cf39bf58afdaabc0b86f141630fb3fd18190294e.
The commit regression to users that define both console=ttyS1
and console=ttyS0 on the command line, see
https://lkml.kernel.org/r/20170509082915.GA13236@bistromath.localdomain
The kernel log messages always appeared only on one serial port. It is
even documented in Documentation/admin-guide/serial-console.rst:
"Note that you can only define one console per device type (serial,
video)."
The above mentioned commit changed the order in which the command line
parameters are searched. As a result, the kernel log messages go to
the last mentioned ttyS* instead of the first one.
We long thought that using two console=ttyS* on the command line
did not make sense. But then we realized that console= parameters
were handled also by systemd, see
http://0pointer.de/blog/projects/serial-console.html
"By default systemd will instantiate one serial-getty@.service on
the main kernel console, if it is not a virtual terminal."
where
"[4] If multiple kernel consoles are used simultaneously, the main
console is the one listed first in /sys/class/tty/console/active,
which is the last one listed on the kernel command line."
This puts the original report into another light. The system is running
in qemu. The first serial port is used to store the messages into a file.
The second one is used to login to the system via a socket. It depends
on systemd and the historic kernel behavior.
By other words, systemd causes that it makes sense to define both
console=ttyS1 console=ttyS0 on the command line. The kernel fix
caused regression related to userspace (systemd) and need to be
reverted.
In addition, it went out that the fix helped only partially.
The messages still were duplicated when the boot console was
removed early by late_initcall(printk_late_init). Then the entire
log was replayed when the same console was registered as a normal one.
Link: 20170606160339.GC7604@pathway.suse.cz
Cc: Aleksey Makarov <aleksey.makarov@linaro.org>
Cc: Sabrina Dubroca <sd@queasysnail.net>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Peter Hurley <peter@hurleysoftware.com>
Cc: Jiri Slaby <jslaby@suse.com>
Cc: Robin Murphy <robin.murphy@arm.com>,
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: "Nair, Jayachandran" <Jayachandran.Nair@cavium.com>
Cc: linux-serial@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Reported-by: Sabrina Dubroca <sd@queasysnail.net>
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
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To enable smp_processor_id() and might_sleep() debug checks earlier, it's
required to add system states between SYSTEM_BOOTING and SYSTEM_RUNNING.
Adjust the system_state check in boot_delay_msec() to handle the extra
states.
Tested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20170516184736.027534895@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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The commit 42a0bb3f71383b457a7d ("printk/nmi: generic solution for safe
printk in NMI") caused that printk stores messages into a temporary
buffer in NMI context.
The buffer is per-CPU and therefore the size is rather limited.
It works quite well for NMI backtraces. But there are longer logs
that might get printed in NMI context, for example, lockdep
warnings, ftrace_dump_on_oops.
The temporary buffer is used to avoid deadlocks caused by
logbuf_lock. Also it is needed to avoid races with the other
temporary buffer that is used when PRINTK_SAFE_CONTEXT is entered.
But the main buffer can be used in NMI if the lock is available
and we did not interrupt PRINTK_SAFE_CONTEXT.
The lock is checked using raw_spin_is_locked(). It might cause
false negatives when the lock is taken on another CPU and
this CPU is in the safe context from other reasons. Note that
the safe context is used also to get console semaphore or when
calling console drivers. For this reason, we do the check in
printk_nmi_enter(). It makes the handling consistent for
the entire NMI handler and avoids reshuffling of the messages.
The patch also defines special printk context that allows
to use printk_deferred() in NMI. Note that we could not flush
the messages to the consoles because console drivers might use
many other internal locks.
The newly created vprintk_deferred() disables the preemption
only around the irq work handling. It is needed there to keep
the consistency between the two per-CPU variables. But there
is no reason to disable preemption around vprintk_emit().
Finally, the patch puts back explicit serialization of the NMI
backtraces from different CPUs. It was removed by the
commit a9edc88093287183ac934b ("x86/nmi: Perform a safe
NMI stack trace on all CPUs"). It was not needed because
the flushing of the temporary per-CPU buffers was serialized.
Link: http://lkml.kernel.org/r/1493912763-24873-1-git-send-email-pmladek@suse.com
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Russell King <rack+kernel@arm.linux.org.uk>
Cc: Daniel Thompson <daniel.thomp |
