Messages in this thread | | | Date | Tue, 30 Jan 2018 10:25:21 +0100 | From | Petr Mladek <> | Subject | [GIT PULL] printk for 4.16 |
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Linus,
please pull the latest printk changes from
git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk.git for-linus
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- Add 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 by passing 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.
This change helped to remove few continuous lines and a less intuitive old API.
- Sergey removed unnecessary memset when processing printk.devkmsg command line option.
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There will be few merge conflicts:
- in Documentation/printk-formats.txt:
- This merge commit removes the obsolete examples for "%pf" format specifier.
- The commit 553d8e8b107159088cc4 ("docs: correct documentation for %pK") removed empty line right below this paragraph.
- scripts/checkpatch.pl:
- This merge commit removes "fF" from the list of valid specifiers. checkpatch.pl is going to suggests "%ps" or "%pS" instead.
- the commit 7b1924a1d930eb27fc ("vsprintf: add printk specifier %px") added the "x" specifier to the list.
- one more in Documentation/printk-formats.txt:
- Jonathan Corbet is going to send conversion of this file to the .rst format.
Just in case, you might find the first two conflicts resolved in git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk.git tmp
---------------------------------------------------------------- Joel Stanley (1): openrisc: Fix conflicting types for _exext and _stext
Petr Mladek (4): printk: Hide console waiter logic into helpers Merge branch 'for-4.16-deprecate-printk-pf' into for-4.16 Merge branch 'for-4.16-print-symbol' into for-4.16 Merge branch 'for-4.16-console-waiter-logic' into for-4.16
Sergey Senozhatsky (24): sched/autogroup: remove unneeded kallsyms include sched/autogroup: move sched.h include printk: add console_msg_format command line option arm: do not use print_symbol() arm64: do not use print_symbol() c6x: do not use print_symbol() ia64: do not use print_symbol() mn10300: do not use print_symbol() sh: do not use print_symbol() unicore32: do not use print_symbol() x86: do not use print_symbol() drivers: do not use print_symbol() sysfs: do not use print_symbol() irq debug: do not use print_symbol() lib: do not use print_symbol() sections: split dereference_function_descriptor() ia64: Add .opd based function descriptor dereference powerpc64: Add .opd based function descriptor dereference parisc64: Add .opd based function descriptor dereference symbol lookup: introduce dereference_symbol_descriptor() checkpatch: add pF/pf deprecation warning kallsyms: remove print_symbol() function printk: Never set console_may_schedule in console_trylock() printk: drop redundant devkmsg_log_str memsets
Steven Rostedt (VMware) (1): printk: Add console owner and waiter logic to load balance console writes
Documentation/admin-guide/kernel-parameters.txt | 14 ++ Documentation/filesystems/sysfs.txt | 4 +- Documentation/printk-formats.txt | 35 ++-- .../translations/zh_CN/filesystems/sysfs.txt | 4 +- arch/arm/kernel/process.c | 5 +- arch/arm64/kernel/process.c | 5 +- arch/c6x/kernel/traps.c | 4 +- arch/ia64/include/asm/sections.h | 10 +- arch/ia64/kernel/module.c | 12 ++ arch/ia64/kernel/process.c | 10 +- arch/ia64/kernel/vmlinux.lds.S | 2 + arch/mn10300/kernel/traps.c | 4 +- arch/openrisc/kernel/traps.c | 3 +- arch/parisc/boot/compressed/vmlinux.lds.S | 2 + arch/parisc/include/asm/sections.h | 6 + arch/parisc/kernel/module.c | 16 ++ arch/parisc/kernel/process.c | 9 + arch/parisc/kernel/vmlinux.lds.S | 2 + arch/powerpc/include/asm/module.h | 3 + arch/powerpc/include/asm/sections.h | 12 ++ arch/powerpc/kernel/module_64.c | 14 ++ arch/powerpc/kernel/vmlinux.lds.S | 2 + arch/sh/kernel/process_32.c | 5 +- arch/unicore32/kernel/process.c | 5 +- arch/x86/kernel/cpu/mcheck/mce.c | 3 +- arch/x86/mm/mmio-mod.c | 5 +- drivers/base/core.c | 5 +- fs/sysfs/file.c | 5 +- include/asm-generic/sections.h | 8 +- include/linux/kallsyms.h | 72 +++++-- include/linux/module.h | 10 + kernel/irq/debug.h | 14 +- kernel/kallsyms.c | 46 ----- kernel/module.c | 6 + kernel/printk/printk.c | 215 ++++++++++++++++++--- kernel/sched/autogroup.c | 5 +- lib/smp_processor_id.c | 3 +- lib/vsprintf.c | 5 +- scripts/checkpatch.pl | 11 +- 39 files changed, 428 insertions(+), 173 deletions(-)
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