Pull printk updates from Petr Mladek:
- Add a console_msg_format command line option:
The value "default" keeps the old "[time stamp] text\n" format. The
value "syslog" allows to see the syslog-like "<log
level>[timestamp] text" format.
This feature was requested by people doing regression tests, for
example, 0day robot. They want to have both filtered and full logs
at hands.
- Reduce the risk of softlockup:
Pass the console owner in a busy loop.
This is a new approach to the old problem. It was first proposed by
Steven Rostedt on Kernel Summit 2017. It marks a context in which
the console_lock owner calls console drivers and could not sleep.
On the other side, printk() callers could detect this state and use
a busy wait instead of a simple console_trylock(). Finally, the
console_lock owner checks if there is a busy waiter at the end of
the special context and eventually passes the console_lock to the
waiter.
The hand-off works surprisingly well and helps in many situations.
Well, there is still a possibility of the softlockup, for example,
when the flood of messages stops and the last owner still has too
much to flush.
There is increasing number of people having problems with
printk-related softlockups. We might eventually need to get better
solution. Anyway, this looks like a good start and promising
direction.
- Do not allow to schedule in console_unlock() called from printk():
This reverts an older controversial commit. The reschedule helped
to avoid softlockups. But it also slowed down the console output.
This patch is obsoleted by the new console waiter logic described
above. In fact, the reschedule made the hand-off less effective.
- Deprecate "%pf" and "%pF" format specifier:
It was needed on ia64, ppc64 and parisc64 to dereference function
descriptors and show the real function address. It is done
transparently by "%ps" and "pS" format specifier now.
Sergey Senozhatsky found that all the function descriptors were in
a special elf section and could be easily detected.
- Remove printk_symbol() API:
It has been obsoleted by "%pS" format specifier, and this change
helped to remove few continuous lines and a less intuitive old API.
- Remove redundant memsets:
Sergey removed unnecessary memset when processing printk.devkmsg
command line option.
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk: (27 commits)
printk: drop redundant devkmsg_log_str memsets
printk: Never set console_may_schedule in console_trylock()
printk: Hide console waiter logic into helpers
printk: Add console owner and waiter logic to load balance console writes
kallsyms: remove print_symbol() function
checkpatch: add pF/pf deprecation warning
symbol lookup: introduce dereference_symbol_descriptor()
parisc64: Add .opd based function descriptor dereference
powerpc64: Add .opd based function descriptor dereference
ia64: Add .opd based function descriptor dereference
sections: split dereference_function_descriptor()
openrisc: Fix conflicting types for _exext and _stext
lib: do not use print_symbol()
irq debug: do not use print_symbol()
sysfs: do not use print_symbol()
drivers: do not use print_symbol()
x86: do not use print_symbol()
unicore32: do not use print_symbol()
sh: do not use print_symbol()
mn10300: do not use print_symbol()
...
No more print_symbol()/__print_symbol() users left, remove these symbols. It was a very old API that encouraged people use continuous lines. It had been obsoleted by %pS format specifier in a normal printk() call. Link: http://lkml.kernel.org/r/20180105102538.GC471@jagdpanzerIV Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Russell King <linux@armlinux.org.uk> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Mark Salter <msalter@redhat.com> Cc: Tony Luck <tony.luck@intel.com> Cc: David Howells <dhowells@redhat.com> Cc: Yoshinori Sato <ysato@users.sourceforge.jp> Cc: Guan Xuetao <gxt@mprc.pku.edu.cn> Cc: Borislav Petkov <bp@alien8.de> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Vineet Gupta <vgupta@synopsys.com> Cc: Fengguang Wu <fengguang.wu@intel.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: LKML <linux-kernel@vger.kernel.org> Cc: linux-arm-kernel@lists.infradead.org Cc: linux-c6x-dev@linux-c6x.org Cc: linux-ia64@vger.kernel.org Cc: linux-am33-list@redhat.com Cc: linux-sh@vger.kernel.org Cc: linux-edac@vger.kernel.org Cc: x86@kernel.org Cc: linux-snps-arc@lists.infradead.org Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Suggested-by: Joe Perches <joe@perches.com> [pmladek@suse.com: updated commit message] Signed-off-by: Petr Mladek <pmladek@suse.com>
dereference_symbol_descriptor() invokes appropriate ARCH specific function descriptor dereference callbacks: - dereference_kernel_function_descriptor() if the pointer is a kernel symbol; - dereference_module_function_descriptor() if the pointer is a module symbol. This is the last step needed to make '%pS/%ps' smart enough to handle function descriptor dereference on affected ARCHs and to retire '%pF/%pf'. To refresh it: Some architectures (ia64, ppc64, parisc64) use an indirect pointer for C function pointers - the function pointer points to a function descriptor and we need to dereference it to get the actual function pointer. Function descriptors live in .opd elf section and all affected ARCHs (ia64, ppc64, parisc64) handle it properly for kernel and modules. So we, technically, can decide if the dereference is needed by simply looking at the pointer: if it belongs to .opd section then we need to dereference it. The kernel and modules have their own .opd sections, obviously, that's why we need to split dereference_function_descriptor() and use separate kernel and module dereference arch callbacks. Link: http://lkml.kernel.org/r/20171206043649.GB15885@jagdpanzerIV Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: James Bottomley <jejb@parisc-linux.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Jessica Yu <jeyu@kernel.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: linux-ia64@vger.kernel.org Cc: linux-parisc@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Tested-by: Tony Luck <tony.luck@intel.com> #ia64 Tested-by: Santosh Sivaraj <santosh@fossix.org> #powerpc Tested-by: Helge Deller <deller@gmx.de> #parisc64 Signed-off-by: Petr Mladek <pmladek@suse.com>
The conditional kallsym hex printing used a special fixed-width '%lx' output (KALLSYM_FMT) in preparation for the hashing of %p, but that series ended up adding a %px specifier to help with the conversions. Use it, and avoid the "print pointer as an unsigned long" code. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull tracing updates from
- allow module init functions to be traced
- clean up some unused or not used by config events (saves space)
- clean up of trace histogram code
- add support for preempt and interrupt enabled/disable events
- other various clean ups
* tag 'trace-v4.15' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: (30 commits)
tracing, thermal: Hide cpu cooling trace events when not in use
tracing, thermal: Hide devfreq trace events when not in use
ftrace: Kill FTRACE_OPS_FL_PER_CPU
perf/ftrace: Small cleanup
perf/ftrace: Fix function trace events
perf/ftrace: Revert ("perf/ftrace: Fix double traces of perf on ftrace:function")
tracing, dma-buf: Remove unused trace event dma_fence_annotate_wait_on
tracing, memcg, vmscan: Hide trace events when not in use
tracing/xen: Hide events that are not used when X86_PAE is not defined
tracing: mark trace_test_buffer as __maybe_unused
printk: Remove superfluous memory barriers from printk_safe
ftrace: Clear hashes of stale ips of init memory
tracing: Add support for preempt and irq enable/disable events
tracing: Prepare to add preempt and irq trace events
ftrace/kallsyms: Have /proc/kallsyms show saved mod init functions
ftrace: Add freeing algorithm to free ftrace_mod_maps
ftrace: Save module init functions kallsyms symbols for tracing
ftrace: Allow module init functions to be traced
ftrace: Add a ftrace_free_mem() function for modules to use
tracing: Reimplement log2
...
The (alleged) users of the module addresses are the same: kernel profiling. So just expose the same helper and format macros, and unify the logic. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Not only is it annoying to have one single flag for all pointers, as if that was a global choice and all kernel pointers are the same, but %pK can't get the 'access' vs 'open' time check right anyway. So make the /proc/kallsyms pointer value code use logic specific to that particular file. We do continue to honor kptr_restrict, but the default (which is unrestricted) is changed to instead take expected users into account, and restrict access by default. Right now the only actual expected user is kernel profiling, which has a separate sysctl flag for kernel profile access. There may be others. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
If a module is loaded while tracing is enabled, then there's a possibility that the module init functions were traced. These functions have their name and address stored by ftrace such that it can translate the function address that is written into the buffer into a human readable function name. As userspace tools may be doing the same, they need a way to map function names to their address as well. This is done through reading /proc/kallsyms. Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
If function tracing is active when the module init functions are freed, then
store them to be referenced by kallsyms. As module init functions can now be
traced on module load, they were useless:
># echo ':mod:snd_seq' > set_ftrace_filter
># echo function > current_tracer
># modprobe snd_seq
># cat trace
# tracer: function
#
# _-----=> irqs-off
# / _----=> need-resched
# | / _---=> hardirq/softirq
# || / _--=> preempt-depth
# ||| / delay
# TASK-PID CPU# |||| TIMESTAMP FUNCTION
# | | | |||| | |
modprobe-2786 [000] .... 3189.037874: 0xffffffffa0860000 <-do_one_initcall
modprobe-2786 [000] .... 3189.037876: 0xffffffffa086004d <-0xffffffffa086000f
modprobe-2786 [000] .... 3189.037876: 0xffffffffa086010d <-0xffffffffa0860018
modprobe-2786 [000] .... 3189.037877: 0xffffffffa086011a <-0xffffffffa0860021
modprobe-2786 [000] .... 3189.037877: 0xffffffffa0860080 <-0xffffffffa086002a
modprobe-2786 [000] .... 3189.039523: 0xffffffffa0860400 <-0xffffffffa0860033
modprobe-2786 [000] .... 3189.039523: 0xffffffffa086038a <-0xffffffffa086041c
modprobe-2786 [000] .... 3189.039591: 0xffffffffa086038a <-0xffffffffa0860436
modprobe-2786 [000] .... 3189.039657: 0xffffffffa086038a <-0xffffffffa0860450
modprobe-2786 [000] .... 3189.039719: 0xffffffffa0860127 <-0xffffffffa086003c
modprobe-2786 [000] .... 3189.039742: snd_seq_create_kernel_client <-0xffffffffa08601f6
When the output is shown, the kallsyms for the module init functions have
already been freed, and the output of the trace can not convert them to
their function names.
Now this looks like this:
# tracer: function
#
# _-----=> irqs-off
# / _----=> need-resched
# | / _---=> hardirq/softirq
# || / _--=> preempt-depth
# ||| / delay
# TASK-PID CPU# |||| TIMESTAMP FUNCTION
# | | | |||| | |
modprobe-2463 [002] .... 174.243237: alsa_seq_init <-do_one_initcall
modprobe-2463 [002] .... 174.243239: client_init_data <-alsa_seq_init
modprobe-2463 [002] .... 174.243240: snd_sequencer_memory_init <-alsa_seq_init
modprobe-2463 [002] .... 174.243240: snd_seq_queues_init <-alsa_seq_init
modprobe-2463 [002] .... 174.243240: snd_sequencer_device_init <-alsa_seq_init
modprobe-2463 [002] .... 174.244860: snd_seq_info_init <-alsa_seq_init
modprobe-2463 [002] .... 174.244861: create_info_entry <-snd_seq_info_init
modprobe-2463 [002] .... 174.244936: create_info_entry <-snd_seq_info_init
modprobe-2463 [002] .... 174.245003: create_info_entry <-snd_seq_info_init
modprobe-2463 [002] .... 174.245072: snd_seq_system_client_init <-alsa_seq_init
modprobe-2463 [002] .... 174.245094: snd_seq_create_kernel_client <-snd_seq_system_client_init
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>