- 20 Nov, 2014 15 commits
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Steven Rostedt (Red Hat) authored
When trigger_all_cpu_backtrace() is called on x86, it will trigger an NMI on each CPU and call show_regs(). But this can lead to a hard lock up if the NMI comes in on another printk(). In order to avoid this, when the NMI triggers, it switches the printk routine for that CPU to call a NMI safe printk function that records the printk in a per_cpu seq_buf descriptor. After all NMIs have finished recording its data, the seq_bufs are printed in a safe context. Link: http://lkml.kernel.org/p/20140619213952.360076309@goodmis.org Link: http://lkml.kernel.org/r/20141115050605.055232587@goodmis.orgTested-by:
Jiri Kosina <jkosina@suse.cz> Acked-by:
Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by:
Petr Mladek <pmladek@suse.cz> Signed-off-by:
Steven Rostedt <rostedt@goodmis.org>
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Steven Rostedt (Red Hat) authored
Being able to divert printk to call another function besides the normal logging is useful for such things like NMI handling. If some functions are to be called from NMI that does printk() it is possible to lock up the box if the nmi handler triggers when another printk is happening. One example of this use is to perform a stack trace on all CPUs via NMI. But if the NMI is to do the printk() it can cause the system to lock up. By allowing the printk to be diverted to another function that can safely record the printk output and then print it when it in a safe context then NMIs will be safe to call these functions like show_regs(). Link: http://lkml.kernel.org/p/20140619213952.209176403@goodmis.orgTested-by:
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Steven Rostedt (Red Hat) authored
The seq_buf functions are rather useful outside of tracing. Instead of having it be dependent on CONFIG_TRACING, move the code into lib/ and allow other users to have access to it even when tracing is not configured. The seq_buf utility is similar to the seq_file utility, but instead of writing sending data back up to userland, it writes it into a buffer defined at seq_buf_init(). This allows us to send a descriptor around that writes printf() formatted strings into it that can be retrieved later. It is currently used by the tracing facility for such things like trace events to convert its binary saved data in the ring buffer into an ASCII human readable context to be displayed in /sys/kernel/debug/trace. It can also be used for doing NMI prints safely from NMI context into the seq_buf and retrieved later and dumped to printk() safely. Doing printk() from an NMI context is dangerous because an NMI can preempt a current printk() and deadlock on it. Link: http://lkml.kernel.org/p/20140619213952.058255809@goodmis.orgTested-by:
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Steven Rostedt (Red Hat) authored
The function bstr_printf() from lib/vsprnintf.c is only available if CONFIG_BINARY_PRINTF is defined. This is due to the only user currently being the tracing infrastructure, which needs to select this config when tracing is configured. Until there is another user of the binary printf formats, this will continue to be the case. Since seq_buf.c is now lives in lib/ and is compiled even without tracing, it must encompass its use of bstr_printf() which is used by seq_buf_printf(). This too is only used by the tracing infrastructure and is still encapsulated by the CONFIG_BINARY_PRINTF. Link: http://lkml.kernel.org/r/20141104160222.969013383@goodmis.orgTested-by:
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Steven Rostedt (Red Hat) authored
Add two helper functions; seq_buf_get_buf() and seq_buf_commit() that are used by seq_buf_path(). This makes the code similar to the seq_file: seq_path() function, and will help to be able to consolidate the functions between seq_file and trace_seq. Link: http://lkml.kernel.org/r/20141104160222.644881406@goodmis.org Link: http://lkml.kernel.org/r/20141114011412.977571447@goodmis.orgTested-by:
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Steven Rostedt (Red Hat) authored
Currently seq_buf is full when all but one byte of the buffer is filled. Change it so that the seq_buf is full when all of the buffer is filled. Some of the functions would fill the buffer completely and report everything was fine. This was inconsistent with the max of size - 1. Changing this to be max of size makes all functions consistent. Link: http://lkml.kernel.org/r/20141104160222.502133196@goodmis.org Link: http://lkml.kernel.org/r/20141114011412.811957882@goodmis.orgTested-by:
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Steven Rostedt (Red Hat) authored
Add a seq_buf_can_fit() helper function that removes the possible mistakes of comparing the seq_buf length plus added data compared to the size of the buffer. Link: http://lkml.kernel.org/r/20141118164025.GL23958@pathway.suse.czReviewed-by:
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Steven Rostedt (Red Hat) authored
To be really paranoid about writing out of bound data in trace_printk_seq(), add another check of len compared to size. Link: http://lkml.kernel.org/r/20141119144004.GB2332@dhcp128.suse.czSuggested-by:
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Steven Rostedt (Red Hat) authored
As the seq_buf->len will soon be +1 size when there's an overflow, we must use trace_seq_used() or seq_buf_used() methods to get the real length. This will prevent buffer overflow issues if just the len of the seq_buf descriptor is used to copy memory. Link: http://lkml.kernel.org/r/20141114121911.09ba3d38@gandalf.local.homeReported-by:
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Steven Rostedt (Red Hat) authored
The function tracing_fill_pipe_page() logic is a little confusing with the use of count saving the seq.len and reusing it. Instead of subtracting a number that is calculated from the saved value of the seq.len from seq.len, just save the seq.len at the start and if we need to reset it, just assign it again. When the seq_buf overflow is len == size + 1, the current logic will break. Changing it to use a saved length for resetting back to the original value is more robust and will work when we change the way seq_buf sets the overflow. Link: http://lkml.kernel.org/r/20141118161546.GJ23958@pathway.suse.czReviewed-by:
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Steven Rostedt (Red Hat) authored
Add a helper function seq_buf_used() that replaces the SEQ_BUF_USED() private macro to let callers have a method to know how much of the seq_buf was written to. Link: http://lkml.kernel.org/r/20141114011412.170377300@goodmis.org Link: http://lkml.kernel.org/r/20141114011413.321654244@goodmis.orgReviewed-by:
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Steven Rostedt (Red Hat) authored
Add a helper function seq_buf_clear() that resets the len and readpos fields of a seq_buf. Currently it is only used in the seq_buf_init() but will be used later when updating the seq_file code. Link: http://lkml.kernel.org/r/20141104160222.352309995@goodmis.orgTested-by:
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Steven Rostedt (Red Hat) authored
In facilitating the conversion of seq_file to use seq_buf, have the seq_buf fields match the types used by seq_file. Link: http://lkml.kernel.org/r/20141104160222.195301024@goodmis.orgTested-by:
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Steven Rostedt (Red Hat) authored
Rewrite seq_buf_path() like it is done in seq_path() and allow it to accept any escape character instead of just "\n". Making seq_buf_path() like seq_path() will help prevent problems when converting seq_file to use the seq_buf logic. Link: http://lkml.kernel.org/r/20141104160222.048795666@goodmis.org Link: http://lkml.kernel.org/r/20141114011412.338523371@goodmis.orgTested-by:
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Steven Rostedt (Red Hat) authored
Create a seq_buf layer that trace_seq sits on. The seq_buf will not be limited to page size. This will allow other usages of seq_buf instead of a hard set PAGE_SIZE one that trace_seq has. Link: http://lkml.kernel.org/r/20141104160221.864997179@goodmis.org Link: http://lkml.kernel.org/r/20141114011412.170377300@goodmis.orgTested-by:
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- 19 Nov, 2014 19 commits
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Markus Elfring authored
The iput() function tests whether its argument is NULL and then returns immediately. Thus the test around the call is not needed. This issue was detected by using the Coccinelle software. Link: http://lkml.kernel.org/r/5468F875.7080907@users.sourceforge.netSigned-off-by:
Markus Elfring <elfring@users.sourceforge.net> Signed-off-by:
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Steven Rostedt (Red Hat) authored
If the trace_seq of ftrace_raw_output_prep() is full this function returns TRACE_TYPE_PARTIAL_LINE, otherwise it returns zero. The problem is that TRACE_TYPE_PARTIAL_LINE happens to be zero! The thing is, the caller of ftrace_raw_output_prep() expects a success to be zero. Change that to expect it to be TRACE_TYPE_HANDLED. Link: http://lkml.kernel.org/r/20141114112522.GA2988@dhcp128.suse.czReminded-by:
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Steven Rostedt (Red Hat) authored
The trace_seq_printf() and friends are used to store strings into a buffer that can be passed around from function to function. If the trace_seq buffer fills up, it will not print any more. The return values were somewhat inconsistant and using trace_seq_has_overflowed() was a better way to know if the write to the trace_seq buffer succeeded or not. Now that all users have removed reading the return value of the printf() type functions, they can safely return void and keep future users of them from reading the inconsistent values as well. Link: http://lkml.kernel.org/r/20141114011411.992510720@goodmis.orgSigned-off-by:
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Steven Rostedt (Red Hat) authored
The functions trace_seq_printf() and friends will not be returning values soon and will be void functions. To know if they succeeded or not, the functions trace_seq_has_overflowed() and trace_handle_return() should be used instead. Reviewed-by:
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Steven Rostedt (Red Hat) authored
The functions trace_seq_printf() and friends will soon no longer have return values. Using trace_seq_has_overflowed() and trace_handle_return() should be used instead. Link: http://lkml.kernel.org/r/20141114011411.693008134@goodmis.org Link: http://lkml.kernel.org/r/20141115050602.333705855@goodmis.orgReviewed-by:
Masami Hiramatsu <masami.hiramatu.pt@hitachi.com> Acked-by:
Srikar Dronamraju <srikar@linux.vnet.ibm.com> Acked-by:
Namhyung Kim <namhyung@kernel.org> Signed-off-by:
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Steven Rostedt (Red Hat) authored
The functions trace_seq_printf() and friends will soon not have a return value and will only be a void function. Use trace_seq_has_overflowed() instead to know if the trace_seq operations succeeded or not. Link: http://lkml.kernel.org/r/20141114011411.530216306@goodmis.orgReviewed-by:
Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Acked-by:
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Steven Rostedt (Red Hat) authored
The return values for trace_seq_printf() and friends are going to be removed and they will become void functions. The mmio tracer checked their return and even did so incorrectly. Some of the funtions which returned the values were never checked themselves. Removing all the checks simplifies the code. Use trace_seq_has_overflowed() and trace_handle_return() where necessary instead. Reviewed-by:
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Steven Rostedt (Red Hat) authored
Instead of checking the return value of trace_seq_printf() and friends for overflowing of the buffer, use the trace_seq_has_overflowed() helper function. This cleans up the code quite a bit and also takes us a step closer to changing the return values of trace_seq_printf() and friends to void. Link: http://lkml.kernel.org/r/20141114011411.181812785@goodmis.orgReviewed-by:
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Steven Rostedt (Red Hat) authored
Instead of doing individual checks all over the place that makes the code very messy. Just check trace_seq_has_overflowed() at the end or in strategic places. This makes the code much cleaner and also helps with getting closer to removing the return values of trace_seq_printf() and friends. Link: http://lkml.kernel.org/r/20141114011410.987913836@goodmis.orgReviewed-by:
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Steven Rostedt (Red Hat) authored
The branch tracer should not be checking the trace_seq_printf() return value as that will soon be void. There's a new trace_handle_return() helper function that will return TRACE_TYPE_PARTIAL_LINE if the trace_seq overflowed and TRACE_TYPE_HANDLED otherwise. Reviewed-by:
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Steven Rostedt (Red Hat) authored
Remove checking the return value of all trace_seq_puts(). It was wrong anyway as only the last return value mattered. But as the trace_seq_puts() is going to be a void function in the future, we should not be checking the return value of it anyway. Just return !trace_seq_has_overflowed() instead. Reviewed-by:
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Steven Rostedt (Red Hat) authored
Checking the return code of every trace_seq_printf() operation and having to return early if it overflowed makes the code messy. Using the new trace_seq_has_overflowed() and trace_handle_return() functions allows us to clean up the code. In the future, trace_seq_printf() and friends will be turning into void functions and not returning a value. The trace_seq_has_overflowed() is to be used instead. This cleanup allows that change to take place. Cc: Jens Axboe <axboe@fb.com> Reviewed-by:
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Steven Rostedt (Red Hat) authored
Adding a trace_seq_has_overflowed() which returns true if the trace_seq had too much written into it allows us to simplify the code. Instead of checking the return value of every call to trace_seq_printf() and friends, they can all be called normally, and at the end we can return !trace_seq_has_overflowed() instead. Several functions also return TRACE_TYPE_PARTIAL_LINE when the trace_seq overflowed and TRACE_TYPE_HANDLED otherwise. Another helper function was created called trace_handle_return() which takes a trace_seq and returns these enums. Using this helper function also simplifies the code. This change also makes it possible to remove the return values of trace_seq_printf() and friends. They should instead just be void functions. Link: http://lkml.kernel.org/r/20141114011410.365183157@goodmis.orgReviewed-by:
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Steven Rostedt (Red Hat) authored
In trace_seq_bitmask() it calls bitmap_scnprintf() not from the current position of the trace_seq buffer (s->buffer + s->len), but instead from the beginning of the buffer (s->buffer). Luckily, the only user of this "ipi_raise tracepoint" uses it as the first parameter, and as such, the start of the temp buffer in include/trace/ftrace.h (see __get_bitmask()). Reported-by:
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Steven Rostedt (Red Hat) authored
Use the helper function trace_seq_buffer_ptr() to get the current location of the next buffer write of a trace_seq object, instead of open coding it. This facilitates the conversion of trace_seq to use seq_buf. Tested-by:
Borislav Petkov <bp@suse.de> Reviewed-by:
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Steven Rostedt (Red Hat) authored
To allow for the restructiong of the trace_seq code, we need users of it to use the helper functions instead of accessing the internals of the trace_seq structure itself. Link: http://lkml.kernel.org/r/20141104160221.585025609@goodmis.orgTested-by:
Paolo Bonzini <pbonzini@redhat.com> Acked-by:
Mark Rustad <mark.d.rustad@intel.com> Reviewed-by:
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Steven Rostedt (Red Hat) authored
Stack traces that happen from function tracing check if the address on the stack is a __kernel_text_address(). That is, is the address kernel code. This calls core_kernel_text() which returns true if the address is part of the builtin kernel code. It also calls is_module_text_address() which returns true if the address belongs to module code. But what is missing is ftrace dynamically allocated trampolines. These trampolines are allocated for individual ftrace_ops that call the ftrace_ops callback functions directly. But if they do a stack trace, the code checking the stack wont detect them as they are neither core kernel code nor module address space. Adding another field to ftrace_ops that also stores the size of the trampoline assigned to it we can create a new function called is_ftrace_trampoline() that returns true if the address is a dynamically allocate ftrace trampoline. Note, it ignores trampolines that are not dynamically allocated as they will return true with the core_kernel_text() function. Link: http://lkml.kernel.org/r/20141119034829.497125839@goodmis.org Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Acked-by:
Thomas Gleixner <tglx@linutronix.de> Signed-off-by:
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Steven Rostedt (Red Hat) authored
When CONFIG_FRAME_POINTERS are enabled, it is required that the ftrace_caller and ftrace_regs_caller trampolines set up frame pointers otherwise a stack trace from a function call wont print the functions that called the trampoline. This is due to a check in __save_stack_address(): #ifdef CONFIG_FRAME_POINTER if (!reliable) return; #endif The "reliable" variable is only set if the function address is equal to contents of the address before the address the frame pointer register points to. If the frame pointer is not set up for the ftrace caller then this will fail the reliable test. It will miss the function that called the trampoline. Worse yet, if fentry is used (gcc 4.6 and beyond), it will also miss the parent, as the fentry is called before the stack frame is set up. That means the bp frame pointer points to the stack of just before the parent function was called. Link: http://lkml.kernel.org/r/20141119034829.355440340@goodmis.org Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: x86@kernel.org Cc: stable@vger.kernel.org # 3.7+ Acked-by:
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Steven Rostedt (Red Hat) authored
The function probe counting for traceon and traceoff suffered a race condition where if the probe was executing on two or more CPUs at the same time, it could decrement the counter by more than one when disabling (or enabling) the tracer only once. The way the traceon and traceoff probes are suppose to work is that they disable (or enable) tracing once per count. If a user were to echo 'schedule:traceoff:3' into set_ftrace_filter, then when the schedule function was called, it would disable tracing. But the count should only be decremented once (to 2). Then if the user enabled tracing again (via tracing_on file), the next call to schedule would disable tracing again and the count would be decremented to 1. But if multiple CPUS called schedule at the same time, it is possible that the count would be decremented more than once because of the simple "count--" used. By reading the count into a local variable and using memory barriers we can guarantee that the count would only be decremented once per disable (or enable). The stack trace probe had a similar race, but here the stack trace will decrement for each time it is called. But this had the read-modify- write race, where it could stack trace more than the number of times that was specified. This case we use a cmpxchg to stack trace only the number of times specified. The dump probes can still use the old "update_count()" function as they only run once, and that is controlled by the dump logic itself. Link: http://lkml.kernel.org/r/20141118134643.4b550ee4@gandalf.local.homeSigned-off-by:
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- 14 Nov, 2014 6 commits
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Byungchul Park authored
Usually, "msecs" notation means milli-seconds, and "usecs" notation means micro-seconds. Since the unit used in the code is micro-seconds, the notation should be replaced from msecs to usecs. Link: http://lkml.kernel.org/r/1415171926-9782-2-git-send-email-byungchul.park@lge.comSigned-off-by:
Byungchul Park <byungchul.park@lge.com> Signed-off-by:
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Daniel Bristot de Oliveira authored
On the function_graph tracer, the print_graph_irq() function prints a trace line with the flag ==========> on an irq handler entry, and the flag <========== on an irq handler return. But when the latency-format is enable, it is not printing the latency-format flags, causing the following error in the trace output: 0) ==========> | 0) d... | smp_apic_timer_interrupt() { This patch fixes this issue by printing the latency-format flags when it is enable. Link: http://lkml.kernel.org/r/7c2e226dac20c940b6242178fab7f0e3c9b5ce58.1415233316.git.bristot@redhat.comReviewed-by:Luis Claudio R. Goncalves <lgoncalv@redhat.com> Signed-off-by:
Daniel Bristot de Oliveira <bristot@redhat.com> Signed-off-by:
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Rasmus Villemoes authored
Printing a single character to a seqfile might as well be done with seq_putc instead of seq_puts; this avoids a strlen() call and a memory access. It also shaves another few bytes off the generated code. Link: http://lkml.kernel.org/r/1415479332-25944-4-git-send-email-linux@rasmusvillemoes.dkSigned-off-by:
Rasmus Villemoes <linux@rasmusvillemoes.dk> Signed-off-by:
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Rasmus Villemoes authored
Consecutive seq_puts calls with literal strings can be merged to a single call. This reduces the size of the generated code, and can also lead to slight .rodata reduction (because of fewer nul and padding bytes). It should also shave a off a few clock cycles. Link: http://lkml.kernel.org/r/1415479332-25944-3-git-send-email-linux@rasmusvillemoes.dkSigned-off-by:
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Rasmus Villemoes authored
Using seq_printf to print a simple string or a single character is a lot more expensive than it needs to be, since seq_puts and seq_putc exist. These patches do seq_printf(m, s) -> seq_puts(m, s) seq_printf(m, "%s", s) -> seq_puts(m, s) seq_printf(m, "%c", c) -> seq_putc(m, c) Subsequent patches will simplify further. Link: http://lkml.kernel.org/r/1415479332-25944-2-git-send-email-linux@rasmusvillemoes.dkSigned-off-by:
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Daniel Thompson authored
Currently kdb's ftdump command will livelock by constantly printk'ing the empty string at KERN_EMERG level if it run when the ftrace system is not in use. This occurs because trace_empty() never returns false when the ring buffers are left at the start of a non-consuming read [launched by ring_buffer_read_start()]. This patch changes the loop exit condition to use the result of trace_find_next_entry_inc(). Effectively this switches the non-consuming kdb dumper to follow the approach of the non-consuming userspace interface [s_next()] rather than the consuming ftrace_dump(). Link: http://lkml.kernel.org/r/1415277716-19419-3-git-send-email-daniel.thompson@linaro.org Cc: Ingo Molnar <mingo@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: John Stultz <john.stultz@linaro.org> Cc: Sumit Semwal <sumit.semwal@linaro.org> Cc: Jason Wessel <jason.wessel@windriver.com> Signed-off-by:
Daniel Thompson <daniel.thompson@linaro.org> Signed-off-by:
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