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* printk: Fix scheduling-while-atomic problem in console_cpu_notify()Paul E. McKenney2012-10-161-1/+0
| | | | | | | | | | | The console_cpu_notify() function runs with interrupts disabled in the CPU_DYING case. It therefore cannot block, for example, as will happen when it calls console_lock(). Therefore, remove the CPU_DYING leg of the switch statement to avoid this problem. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* printk: Fix calculation of length used to discard recordsJeff Mahoney2012-08-121-0/+2
| | | | | | | | | | | | | | | | | | | | | | While tracking down a weird buffer overflow issue in a program that looked to be sane, I started double checking the length returned by syslog(SYSLOG_ACTION_READ_ALL, ...) to make sure it wasn't overflowing the buffer. Sure enough, it was. I saw this in strace: 11339 syslog(SYSLOG_ACTION_READ_ALL, "<5>[244017.708129] REISERFS (dev"..., 8192) = 8279 It turns out that the loops that calculate how much space the entries will take when they're copied don't include the newlines and prefixes that will be included in the final output since prev flags is passed as zero. This patch properly accounts for it and fixes the overflow. CC: stable@kernel.org Signed-off-by: Jeff Mahoney <jeffm@suse.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* printk: only look for prefix levels in kernel messagesJoe Perches2012-07-301-15/+17
| | | | | | | | | | vprintk_emit() prefix parsing should only be done for internal kernel messages. This allows existing behavior to be kept in all cases. Signed-off-by: Joe Perches <joe@perches.com> Cc: Kay Sievers <kay@vrfy.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* printk: add generic functions to find KERN_<LEVEL> headersJoe Perches2012-07-301-5/+9
| | | | | | | | | | | | | | | | | | The current form of a KERN_<LEVEL> is "<.>". Add printk_get_level and printk_skip_level functions to handle these formats. These functions centralize tests of KERN_<LEVEL> so a future modification can change the KERN_<LEVEL> style and shorten the number of bytes consumed by these headers. [akpm@linux-foundation.org: fix build error and warning] Signed-off-by: Joe Perches <joe@perches.com> Cc: Kay Sievers <kay.sievers@vrfy.org> Cc: Wu Fengguang <wfg@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* kmsg: /dev/kmsg - properly return possible copy_from_user() failureKay Sievers2012-07-301-1/+3
| | | | | | | Reported-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* Merge tag 'driver-core-3.6-rc1' of ↵Linus Torvalds2012-07-261-38/+121
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core Pull driver core changes from Greg Kroah-Hartman: "Here's the big driver core pull request for 3.6-rc1. Unlike 3.5, this kernel should be a lot tamer, with the printk changes now settled down. All we have here is some extcon driver updates, w1 driver updates, a few printk cleanups that weren't needed for 3.5, but are good to have now, and some other minor fixes/changes in the driver core. All of these have been in the linux-next releases for a while now. Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>" * tag 'driver-core-3.6-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core: (38 commits) printk: Export struct log size and member offsets through vmcoreinfo Drivers: hv: Change the hex constant to a decimal constant driver core: don't trigger uevent after failure extcon: MAX77693: Add extcon-max77693 driver to support Maxim MAX77693 MUIC device sysfs: fail dentry revalidation after namespace change fix sysfs: fail dentry revalidation after namespace change extcon: spelling of detach in function doc extcon: arizona: Stop microphone detection if we give up on it extcon: arizona: Update cable reporting calls and split headset PM / Runtime: Do not increment device usage counts before probing kmsg - do not flush partial lines when the console is busy kmsg - export "continuation record" flag to /dev/kmsg kmsg - avoid warning for CONFIG_PRINTK=n compilations kmsg - properly print over-long continuation lines driver-core: Use kobj_to_dev instead of re-implementing it driver-core: Move kobj_to_dev from genhd.h to device.h driver core: Move deferred devices to the end of dpm_list before probing driver core: move uevent call to driver_register driver core: fix shutdown races with probe/remove(v3) Extcon: Arizona: Add driver for Wolfson Arizona class devices ...
| * printk: Export struct log size and member offsets through vmcoreinfoVivek Goyal2012-07-191-0/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | There are tools like makedumpfile and vmcore-dmesg which can extract kernel log buffer from vmcore. Since we introduced structured logging, that functionality is broken. Now user space tools need to know about "struct log" and offsets of various fields to be able to parse struct log data and extract text message or dictonary. This patch exports some of the fields. Currently I am not exporting log "level" info as that is a bitfield and offsetof() bitfields can't be calculated. But if people start asking for log level info in the output then we probably either need to seprate out "level" or use bit shift operations for flags and level. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Acked-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| * kmsg - do not flush partial lines when the console is busyKay Sievers2012-07-161-25/+68
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Fragments of continuation lines are flushed to the console immediately. In case the console is locked, the fragment must be queued up in the cont buffer. If the the console is busy and the continuation line is complete, but no part of it was written to the console up to this point, we can just store the entire line as a regular record and free the buffer earlier. If the console is busy and earlier messages are already queued up, we should not flush the fragments of continuation lines, but store them after the queued up messages, to ensure the proper ordering. This keeps the console output better readable in case printk()s race against each other, or we receive over-long continuation lines we need to flush. Signed-off-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| * kmsg - export "continuation record" flag to /dev/kmsgKay Sievers2012-07-161-2/+21
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | In some cases we are forced to store individual records for a continuation line print. Export a flag to allow the external re-construction of the line. The flag allows us to apply a similar logic externally which is used internally when the console, /proc/kmsg or the syslog() output is printed. $ cat /dev/kmsg 4,165,0,-;Free swap = 0kB 4,166,0,-;Total swap = 0kB 6,167,0,c;[ 4,168,0,+;0 4,169,0,+;1 4,170,0,+;2 4,171,0,+;3 4,172,0,+;] 6,173,0,-;[0 1 2 3 ] 6,174,0,-;Console: colour VGA+ 80x25 6,175,0,-;console [tty0] enabled Signed-off-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| * kmsg - avoid warning for CONFIG_PRINTK=n compilationsKay Sievers2012-07-161-2/+9
| | | | | | | | | | Signed-off-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| * kmsg - properly print over-long continuation linesKay Sievers2012-07-161-14/+19
| | | | | | | | | | | | | | | | | | | | | | Reserve PREFIX_MAX bytes in the LOG_LINE_MAX line when buffering a continuation line, to be able to properly prefix the LOG_LINE_MAX line with the syslog prefix and timestamp when printing it. Reported-By: Dave Jones <davej@redhat.com> Signed-off-by: Kay Sievers <kay@vrfy.org> Cc: stable <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* | printk: Implement some unlocked kmsg_dump functionsAnton Vorontsov2012-07-211-13/+55
| | | | | | | | | | | | | | | | | | | | | | | | If used from KDB, the locked variants are prone to deadlocks (suppose we got to the debugger w/ the logbuf lock held). So, we have to implement a few routines that grab no logbuf lock. Yet we don't need these functions in modules, so we don't export them. Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | printk: Remove kdb_syslog_dataAnton Vorontsov2012-07-211-15/+0
|/ | | | | | | The function is no longer needed, so remove it. Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* kmsg: merge continuation records while printingKay Sievers2012-07-091-42/+78
| | | | | | | | | | | | | | | | | In (the unlikely) case our continuation merge buffer is busy, we unfortunately can not merge further continuation printk()s into a single record and have to store them separately, which leads to split-up output of these lines when they are printed. Add some flags about newlines and prefix existence to these records and try to reconstruct the full line again, when the separated records are printed. Reported-By: Michael Neuling <mikey@neuling.org> Cc: Dave Jones <davej@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Tested-By: Michael Neuling <mikey@neuling.org> Signed-off-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* kmsg: /proc/kmsg - support reading of partial log recordsKay Sievers2012-07-091-8/+20
| | | | | | | | | | | | | | Restore support for partial reads of any size on /proc/kmsg, in case the supplied read buffer is smaller than the record size. Some people seem to think is is ia good idea to run: $ dd if=/proc/kmsg bs=1 of=... as a klog bridge. Resolves-bug: https://bugzilla.kernel.org/show_bug.cgi?id=44211 Reported-by: Jukka Ollila <jiiksteri@gmail.com> Signed-off-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* kmsg: make sure all messages reach a newly registered boot consoleKay Sievers2012-07-061-0/+6
| | | | | | | | | | | | We suppress printing kmsg records to the console, which are already printed immediately while we have received their fragments. Newly registered boot consoles print the entire kmsg buffer during registration. Clear the console-suppress flag after we skipped the record during its first storage, so any later print will see these records as usual. Signed-off-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* kmsg: properly handle concurrent non-blocking read() from /proc/kmsgKay Sievers2012-07-061-8/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The /proc/kmsg read() interface is internally simply wired up to a sequence of syslog() syscalls, which might are racy between their checks and actions, regarding concurrency. In the (very uncommon) case of concurrent readers of /dev/kmsg, relying on usual O_NONBLOCK behavior, the recently introduced mutex might block an O_NONBLOCK reader in read(), when poll() returns for it, but another process has already read the data in the meantime. We've seen that while running artificial test setups and tools that "fight" about /proc/kmsg data. This restores the original /proc/kmsg behavior, where in case of concurrent read()s, poll() might wake up but the read() syscall will just return 0 to the caller, while another process has "stolen" the data. This is in the general case not the expected behavior, but it is the exact same one, that can easily be triggered with a 3.4 kernel, and some tools might just rely on it. The mutex is not needed, the original integrity issue which introduced it, is in the meantime covered by: "fill buffer with more than a single message for SYSLOG_ACTION_READ" 116e90b23f74d303e8d607c7a7d54f60f14ab9f2 Cc: Yuanhan Liu <yuanhan.liu@linux.intel.com> Acked-by: Jan Beulich <jbeulich@suse.com> Signed-off-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* kmsg: add the facility number to the syslog prefixKay Sievers2012-07-061-4/+7
| | | | | | | | | | | | | | | | | After the recent split of facility and level into separate variables, we miss the facility value (always 0 for kernel-originated messages) in the syslog prefix. On Tue, Jul 3, 2012 at 12:45 PM, Dan Carpenter <dan.carpenter@oracle.com> wrote: > Static checkers complain about the impossible condition here. > > In 084681d14e ('printk: flush continuation lines immediately to > console'), we changed msg->level from being a u16 to being an unsigned > 3 bit bitfield. Cc: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* kmsg: escape the backslash character while exporting dataKay Sievers2012-07-061-2/+2
| | | | | | | | | | | | | | Non-printable characters in the log data are hex-escaped to ensure safe post processing. We need to escape a backslash we find in the data, to be able to distinguish it from a backslash we add for the escaping. Also escape the non-printable character 127. Thanks to Miloslav Trmac for the heads up. Reported-by: Michael Neuling <mikey@neuling.org> Signed-off-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* printk: replacing the raw_spin_lock/unlock with raw_spin_lock/unlock_irqliu chuansheng2012-07-061-12/+12
| | | | | | | | | | | | | | | | | In function devkmsg_read/writev/llseek/poll/open()..., the function raw_spin_lock/unlock is used, there is potential deadlock case happening. CPU1: thread1 doing the cat /dev/kmsg: raw_spin_lock(&logbuf_lock); while (user->seq == log_next_seq) { when thread1 run here, at this time one interrupt is coming on CPU1 and running based on this thread,if the interrupt handle called the printk which need the logbuf_lock spin also, it will cause deadlock. So we should use raw_spin_lock/unlock_irq here. Acked-by: Kay Sievers <kay@vrfy.org> Signed-off-by: liu chuansheng <chuansheng.liu@intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* printk.c: fix kernel-doc warningsRandy Dunlap2012-06-301-1/+1
| | | | | | | | | | Fix kernel-doc warnings in printk.c: use correct parameter name. Warning(kernel/printk.c:2429): No description found for parameter 'buf' Warning(kernel/printk.c:2429): Excess function parameter 'line' description in 'kmsg_dump_get_buffer' Signed-off-by: Randy Dunlap <rdunlap@xenotime.net> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* printk: Optimize if statement logic where newline existsSteven Rostedt2012-06-291-7/+6
| | | | | | | | | | | | | | | In reviewing Kay's fix up patch: "printk: Have printk() never buffer its data", I found two if statements that could be combined and optimized. Put together the two 'cont.len && cont.owner == current' if statements into a single one, and check if we need to call cont_add(). This also removes the unneeded double cont_flush() calls. Link: http://lkml.kernel.org/r/1340869133.876.10.camel@mop Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Cc: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* printk: flush continuation lines immediately to consoleKay Sievers2012-06-291-68/+176
| | | | | | | | | | | | | | | | | | | | | | Continuation lines are buffered internally, intended to merge the chunked printk()s into a single record, and to isolate potentially racy continuation users from usual terminated line users. This though, has the effect that partial lines are not printed to the console in the moment they are emitted. In case the kernel crashes in the meantime, the potentially interesting printed information would never reach the consoles. Here we share the continuation buffer with the console copy logic, and partial lines are always immediately flushed to the available consoles. They are still buffered internally to improve the readability and integrity of the messages and minimize the amount of needed record headers to store. Signed-off-by: Kay Sievers <kay@vrfy.org> Tested-by: Steven Rostedt <rostedt@goodmis.org> Acked-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* syslog: fill buffer with more than a single message for SYSLOG_ACTION_READJan Beulich2012-06-261-14/+37
| | | | | | | | | | | | | | | | | | | | | | | | | | | The recent changes to the printk buffer management resulted in SYSLOG_ACTION_READ to only return a single message, whereas previously the buffer would get filled as much as possible. As, when too small to fit everything, filling it to the last byte would be pretty ugly with the new code, the patch arranges for as many messages as possible to get returned in a single invocation. User space tools in at least all SLES versions depend on the old behavior. This at once addresses the issue attempted to get fixed with commit b56a39ac263e5b8cafedd551a49c2105e68b98c2 ("printk: return -EINVAL if the message len is bigger than the buf size"), and since that commit widened the possibility for losing a message altogether, the patch here assumes that this other commit would get reverted first (otherwise the patch here won't apply). Furthermore, this patch also addresses the problem dealt with in commit 4a77a5a06ec66ed05199b301e7c25f42f979afdc ("printk: use mutex lock to stop syslog_seq from going wild"), so I'd recommend reverting that one too (albeit there's no direct collision between the two). Signed-off-by: Jan Beulich <jbeulich@suse.com> Acked-by: Kay Sievers <kay@vrfy.org> Cc: Yuanhan Liu <yuanhan.liu@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* Revert "printk: return -EINVAL if the message len is bigger than the buf size"Greg Kroah-Hartman2012-06-261-3/+1
| | | | | | | | | | | | This reverts commit b56a39ac263e5b8cafedd551a49c2105e68b98c2. A better patch from Jan will follow this to resolve the issue. Acked-by: Kay Sievers <kay@vrfy.org> Cc: Fengguang Wu <wfg@linux.intel.com> Cc: Yuanhan Liu <yuanhan.liu@linux.intel.com> Cc: Jan Beulich <JBeulich@suse.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* printk: fix regression in SYSLOG_ACTION_CLEARAlan Stern2012-06-251-0/+1
| | | | | | | | | | | | | | | | Commit 7ff9554bb578ba02166071d2d487b7fc7d860d62 (printk: convert byte-buffer to variable-length record buffer) introduced a regression by accidentally removing a "break" statement from inside the big switch in printk's do_syslog(). The symptom of this bug is that the "dmesg -C" command doesn't only clear the kernel's log buffer; it also disables console logging. This patch (as1561) fixes the regression by adding the missing "break". Signed-off-by: Alan Stern <stern@rowland.harvard.edu> CC: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* printk: return -EINVAL if the message len is bigger than the buf sizeYuanhan Liu2012-06-161-1/+3
| | | | | | | | | | Just like what devkmsg_read() does, return -EINVAL if the message len is bigger than the buf size, or it will trigger a segfault error. Acked-by: Kay Sievers <kay@vrfy.org> Acked-by: Fengguang Wu <wfg@linux.intel.com> Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* printk: use mutex lock to stop syslog_seq from going wildYuanhan Liu2012-06-161-2/+11
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Although syslog_seq and log_next_seq stuff are protected by logbuf_lock spin log, it's not enough. Say we have two processes A and B, and let syslog_seq = N, while log_next_seq = N + 1, and the two processes both come to syslog_print at almost the same time. And No matter which process get the spin lock first, it will increase syslog_seq by one, then release spin lock; thus later, another process increase syslog_seq by one again. In this case, syslog_seq is bigger than syslog_next_seq. And latter, it would make: wait_event_interruptiable(log_wait, syslog != log_next_seq) don't wait any more even there is no new write comes. Thus it introduce a infinite loop reading. I can easily see this kind of issue by the following steps: # cat /proc/kmsg # at meantime, I don't kill rsyslog # So they are the two processes. # xinit # I added drm.debug=6 in the kernel parameter line, # so that it will produce lots of message and let that # issue happen It's 100% reproducable on my side. And my disk will be filled up by /var/log/messages in a quite short time. So, introduce a mutex_lock to stop syslog_seq from going wild just like what devkmsg_read() does. It does fix this issue as expected. v2: use mutex_lock_interruptiable() instead (comments from Kay) Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com> Reviewed-by: Fengguang Wu <fengguang.wu@intel.com> Acked-By: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* kmsg - kmsg_dump() use iterator to receive log buffer contentKay Sievers2012-06-151-28/+192
| | | | | | | | | | | | | | | | | Provide an iterator to receive the log buffer content, and convert all kmsg_dump() users to it. The structured data in the kmsg buffer now contains binary data, which should no longer be copied verbatim to the kmsg_dump() users. The iterator should provide reliable access to the buffer data, and also supports proper log line-aware chunking of data while iterating. Signed-off-by: Kay Sievers <kay@vrfy.org> Tested-by: Tony Luck <tony.luck@intel.com> Reported-by: Anton Vorontsov <anton.vorontsov@linaro.org> Tested-by: Anton Vorontsov <anton.vorontsov@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* printk: Fix alignment of buf causing crash on ARM EABIAndrew Lunn2012-06-121-2/+2
| | | | | | | | | | | | | | | | | | | | Commit 7ff9554bb578ba02166071d2d487b7fc7d860d62, printk: convert byte-buffer to variable-length record buffer, causes systems using EABI to crash very early in the boot cycle. The first entry in struct log is a u64, which for EABI must be 8 byte aligned. Make use of __alignof__() so the compiler to decide the alignment, but allow it to be overridden using CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS, for systems which can perform unaligned access and want to save a few bytes of space. Tested on Orion5x and Kirkwood. Signed-off-by: Andrew Lunn <andrew@lunn.ch> Tested-by: Stephen Warren <swarren@wwwdotorg.org> Acked-by: Stephen Warren <swarren@wwwdotorg.org> Acked-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* printk() - isolate KERN_CONT users from ordinary complete linesKay Sievers2012-05-141-44/+61
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Arrange the continuation printk() buffering to be fully separated from the ordinary full line users. Limit the exposure to races and wrong printk() line merges to users of continuation only. Ordinary full line users racing against continuation users will no longer affect each other. Multiple continuation users from different threads, racing against each other will not wrongly be merged into a single line, but printed as separate lines. Test output of a kernel module which starts two separate threads which race against each other, one of them printing a single full terminated line: printk("(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA)\n"); The other one printing the line, every character separate in a continuation loop: printk("(C"); for (i = 0; i < 58; i++) printk(KERN_CONT "C"); printk(KERN_CONT "C)\n"); Behavior of single and non-thread-aware printk() buffer: # modprobe printk-race printk test init (CC(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) C(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) CC(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) C(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) CC(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) C(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) C(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) CC(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) C(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) C(AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC) (CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC) New behavior with separate and thread-aware continuation buffer: # modprobe printk-race printk test init (AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) (AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) (AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) (CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC) (AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) (AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) (AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) (AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA) (CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC) (CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC) Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Joe Perches <joe@perches.com> Cc: Ted Ts'o <tytso@mit.edu> Cc: Ingo Molnar <mingo@kernel.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Sasha Levin <levinsasha928@gmail.com> Signed-off-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* printk() - restore prefix/timestamp printing for multi-newline stringsKay Sievers2012-05-141-51/+76
| | | | | | | | | | | Calls like: printk("\n *** DEADLOCK ***\n\n"); will print 3 properly indented, separated, syslog + timestamp prefixed lines in the log output. Reported-By: Sasha Levin <levinsasha928@gmail.com> Signed-off-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* printk: add stub for prepend_timestamp()Randy Dunlap2012-05-111-0/+4
| | | | | | | | | | | Add a stub for prepend_timestamp() when CONFIG_PRINTK is not enabled. Fixes this build error: kernel/printk.c:1770:3: error: implicit declaration of function 'prepend_timestamp' Cc: Kay Sievers <kay@vrfy.org> Signed-off-by: Randy Dunlap <rdunlap@xenotime.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* printk: correctly align __log_bufStephen Warren2012-05-101-7/+6
| | | | | | | | | | | __log_buf must be aligned, because a 64-bit value is written directly to it as part of struct log. Alignment of the log entries is typically handled by log_store(), but this only triggers for subsequent entries, not the very first (or wrapped) entries. Cc: Kay Sievers <kay@vrfy.org> Signed-off-by: Stephen Warren <swarren@nvidia.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* printk() - restore timestamp printing at console outputKay Sievers2012-05-091-17/+26
| | | | | | | | | | | | | | | | | The output of the timestamps got lost with the conversion of the kmsg buffer to records; restore the old behavior. Document, that CONFIG_PRINTK_TIME now only controls the output of the timestamps in the syslog() system call and on the console, and not the recording of the timestamps. Cc: Joe Perches <joe@perches.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Sasha Levin <levinsasha928@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Reported-by: Yinghai Lu <yinghai@kernel.org> Signed-off-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* printk() - do not merge continuation lines of different threadsKay Sievers2012-05-091-9/+10
| | | | | | | | | | | | | | | | This prevents the merging of printk() continuation lines of different threads, in the case they race against each other. It should properly isolate "atomic" single-line printk() users from continuation users, to make sure the single-line users will never be merged with the racy continuation ones. Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Sasha Levin <levinsasha928@gmail.com> Signed-off-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* printk - fix compilation for CONFIG_PRINTK=nKay Sievers2012-05-091-19/+22
| | | | | | Reported-by: Randy Dunlap <rdunlap@xenotime.net> Signed-off-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* kmsg: use do_div() to divide 64bit integerKay Sievers2012-05-081-1/+4
| | | | | | | | | | | | On Tue, May 8, 2012 at 10:02 AM, Stephen Rothwell <sfr@canb.auug.org.au> wrote: > kernel/built-in.o: In function `devkmsg_read': > printk.c:(.text+0x27e8): undefined reference to `__udivdi3' > Most probably the "msg->ts_nsec / 1000" since > ts_nsec is a u64 and this is a 32 bit build ... Reported-by: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* kmsg: export printk records to the /dev/kmsg interfaceKay Sievers2012-05-071-0/+313
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Support for multiple concurrent readers of /dev/kmsg, with read(), seek(), poll() support. Output of message sequence numbers, to allow userspace log consumers to reliably reconnect and reconstruct their state at any given time. After open("/dev/kmsg"), read() always returns *all* buffered records. If only future messages should be read, SEEK_END can be used. In case records get overwritten while /dev/kmsg is held open, or records get faster overwritten than they are read, the next read() will return -EPIPE and the current reading position gets updated to the next available record. The passed sequence numbers allow the log consumer to calculate the amount of lost messages. [root@mop ~]# cat /dev/kmsg 5,0,0;Linux version 3.4.0-rc1+ (kay@mop) (gcc version 4.7.0 20120315 ... 6,159,423091;ACPI: PCI Root Bridge [PCI0] (domain 0000 [bus 00-ff]) 7,160,424069;pci_root PNP0A03:00: host bridge window [io 0x0000-0x0cf7] (ignored) SUBSYSTEM=acpi DEVICE=+acpi:PNP0A03:00 6,339,5140900;NET: Registered protocol family 10 30,340,5690716;udevd[80]: starting version 181 6,341,6081421;FDC 0 is a S82078B 6,345,6154686;microcode: CPU0 sig=0x623, pf=0x0, revision=0x0 7,346,6156968;sr 1:0:0:0: Attached scsi CD-ROM sr0 SUBSYSTEM=scsi DEVICE=+scsi:1:0:0:0 6,347,6289375;microcode: CPU1 sig=0x623, pf=0x0, revision=0x0 Cc: Karel Zak <kzak@redhat.com> Tested-by: William Douglas <william.douglas@intel.com> Signed-off-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* printk: convert byte-buffer to variable-length record bufferKay Sievers2012-05-071-424/+590
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | - Record-based stream instead of the traditional byte stream buffer. All records carry a 64 bit timestamp, the syslog facility and priority in the record header. - Records consume almost the same amount, sometimes less memory than the traditional byte stream buffer (if printk_time is enabled). The record header is 16 bytes long, plus some padding bytes at the end if needed. The byte-stream buffer needed 3 chars for the syslog prefix, 15 char for the timestamp and a newline. - Buffer management is based on message sequence numbers. When records need to be discarded, the reading heads move on to the next full record. Unlike the byte-stream buffer, no old logged lines get truncated or partly overwritten by new ones. Sequence numbers also allow consumers of the log stream to get notified if any message in the stream they are about to read gets discarded during the time of reading. - Better buffered IO support for KERN_CONT continuation lines, when printk() is called multiple times for a single line. The use of KERN_CONT is now mandatory to use continuation; a few places in the kernel need trivial fixes here. The buffering could possibly be extended to per-cpu variables to allow better thread-safety for multiple printk() invocations for a single line. - Full-featured syslog facility value support. Different facilities can tag their messages. All userspace-injected messages enforce a facility value > 0 now, to be able to reliably distinguish them from the kernel-generated messages. Independent subsystems like a baseband processor running its own firmware, or a kernel-related userspace process can use their own unique facility values. Multiple independent log streams can co-exist that way in the same buffer. All share the same global sequence number counter to ensure proper ordering (and interleaving) and to allow the consumers of the log to reliably correlate the events from different facilities. Tested-by: William Douglas <william.douglas@intel.com> Signed-off-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* Merge branch 'sched-core-for-linus' of ↵Linus Torvalds2012-03-201-3/+37
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull scheduler changes for v3.4 from Ingo Molnar * 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (27 commits) printk: Make it compile with !CONFIG_PRINTK sched/x86: Fix overflow in cyc2ns_offset sched: Fix nohz load accounting -- again! sched: Update yield() docs printk/sched: Introduce special printk_sched() for those awkward moments sched/nohz: Correctly initialize 'next_balance' in 'nohz' idle balancer sched: Cleanup cpu_active madness sched: Fix load-balance wreckage sched: Clean up parameter passing of proc_sched_autogroup_set_nice() sched: Ditch per cgroup task lists for load-balancing sched: Rename load-balancing fields sched: Move load-balancing arguments into helper struct sched/rt: Do not submit new work when PI-blocked sched/rt: Prevent idle task boosting sched/wait: Add __wake_up_all_locked() API sched/rt: Document scheduler related skip-resched-check sites sched/rt: Use schedule_preempt_disabled() sched/rt: Add schedule_preempt_disabled() sched/rt: Do not throttle when PI boosting sched/rt: Keep period timer ticking when rt throttling is active ...
| * printk: Make it compile with !CONFIG_PRINTKPeter Zijlstra2012-03-151-20/+20
| | | | | | | | | | | | | | | | | | | | | | | | Commit 3ccf3e830615 ("printk/sched: Introduce special printk_sched() for those awkward moments") overlooked an #ifdef, so move code around to respect these directives. Reported-by: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Randy Dunlap <rdunlap@xenotime.net> Link: http://lkml.kernel.org/r/1331811337.18960.179.camel@twins Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * Merge tag 'v3.3-rc7' into sched/coreIngo Molnar2012-03-131-0/+6
| |\ | | | | | | | | | | | | | | | Merge reason: merge back final fixes, prepare for the merge window. Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * | printk/sched: Introduce special printk_sched() for those awkward momentsPeter Zijlstra2012-03-121-3/+37
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | There's a few awkward printk()s inside of scheduler guts that people prefer to keep but really are rather deadlock prone. Fudge around it by storing the text in a per-cpu buffer and poll it using the existing printk_tick() handler. This will drop output when its more frequent than once a tick, however only the affinity thing could possible go that fast and for that just one should suffice to notify the admin he's done something silly.. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Link: http://lkml.kernel.org/n/tip-wua3lmkt3dg8nfts66o6brne@git.kernel.org Signed-off-by: Ingo Molnar <mingo@elte.hu>
* | | Merge branch 'perf/urgent' into perf/coreIngo Molnar2012-03-121-0/+6
|\ \ \ | | |/ | |/| | | | | | | | | | Merge reason: We are going to queue up a dependent patch. Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * | kmsg_dump: don't run on non-error paths by defaultMatthew Garrett2012-03-051-0/+6
| |/ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Since commit 04c6862c055f ("kmsg_dump: add kmsg_dump() calls to the reboot, halt, poweroff and emergency_restart paths"), kmsg_dump() gets run on normal paths including poweroff and reboot. This is less than ideal given pstore implementations that can only represent single backtraces, since a reboot may overwrite a stored oops before it's been picked up by userspace. In addition, some pstore backends may have low performance and provide a significant delay in reboot as a result. This patch adds a printk.always_kmsg_dump kernel parameter (which can also be changed from userspace). Without it, the code will only be run on failure paths rather than on normal paths. The option can be enabled in environments where there's a desire to attempt to audit whether or not a reboot was cleanly requested or not. Signed-off-by: Matthew Garrett <mjg@redhat.com> Acked-by: Seiji Aguchi <seiji.aguchi@hds.com> Cc: Seiji Aguchi <seiji.aguchi@hds.com> Cc: David Woodhouse <dwmw2@infradead.org> Cc: Marco Stornelli <marco.stornelli@gmail.com> Cc: Artem Bityutskiy <Artem.Bityutskiy@nokia.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Don Zickus <dzickus@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* / printk/tracing: Add console output tracingJohannes Berg2012-02-131-0/+5
|/ | | | | | | | | | | | | | | | | Add a printk.console trace point to record any printk messages into the trace, regardless of the current console loglevel. This can help correlate (existing) printk debugging with other tracing. Link: http://lkml.kernel.org/r/1322161388.5366.54.camel@jlt3.sipsolutions.net Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Christoph Hellwig <hch@infradead.org> Cc: Ingo Molnar <mingo@redhat.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Johannes Berg <johannes.berg@intel.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
* module_param: make bool parameters really bool (core code)Rusty Russell2012-01-131-4/+4
| | | | | | | | | | | module_param(bool) used to counter-intuitively take an int. In fddd5201 (mid-2009) we allowed bool or int/unsigned int using a messy trick. It's time to remove the int/unsigned int option. For this version it'll simply give a warning, but it'll break next kernel version. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
* printk: fix unnecessary module_param_name.Rusty Russell2012-01-131-1/+1
| | | | | | | | You don't need module_param_name if the name is the same! Cc: Yanmin Zhang <yanmin_zhang@linux.intel.com> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
* Merge branch 'core-printk-for-linus' of ↵Linus Torvalds2012-01-061-5/+4
|\ | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip * 'core-printk-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: printk, lockdep: Switch to tracked irq ops printk, lockdep: Remove superfluous preempt_disable() printk, lockdep: Disable lock debugging on zap_locks()
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