linux/kernel/trace/ring_buffer.c, branch v5.11

Merge tag 'trace-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

2020-12-17T21:22:17Z

Pull tracing updates from Steven Rostedt: "The major update to this release is that there's a new arch config option called CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS. Currently, only x86_64 enables it. All the ftrace callbacks now take a struct ftrace_regs instead of a struct pt_regs. If the architecture has HAVE_DYNAMIC_FTRACE_WITH_ARGS enabled, then the ftrace_regs will have enough information to read the arguments of the function being traced, as well as access to the stack pointer. This way, if a user (like live kernel patching) only cares about the arguments, then it can avoid using the heavier weight "regs" callback, that puts in enough information in the struct ftrace_regs to simulate a breakpoint exception (needed for kprobes). A new config option that audits the timestamps of the ftrace ring buffer at most every event recorded. Ftrace recursion protection has been cleaned up to move the protection to the callback itself (this saves on an extra function call for those callbacks). Perf now handles its own RCU protection and does not depend on ftrace to do it for it (saving on that extra function call). New debug option to add "recursed_functions" file to tracefs that lists all the places that triggered the recursion protection of the function tracer. This will show where things need to be fixed as recursion slows down the function tracer. The eval enum mapping updates done at boot up are now offloaded to a work queue, as it caused a noticeable pause on slow embedded boards. Various clean ups and last minute fixes" * tag 'trace-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: (33 commits) tracing: Offload eval map updates to a work queue Revert: "ring-buffer: Remove HAVE_64BIT_ALIGNED_ACCESS" ring-buffer: Add rb_check_bpage in __rb_allocate_pages ring-buffer: Fix two typos in comments tracing: Drop unneeded assignment in ring_buffer_resize() tracing: Disable ftrace selftests when any tracer is running seq_buf: Avoid type mismatch for seq_buf_init ring-buffer: Fix a typo in function description ring-buffer: Remove obsolete rb_event_is_commit() ring-buffer: Add test to validate the time stamp deltas ftrace/documentation: Fix RST C code blocks tracing: Clean up after filter logic rewriting tracing: Remove the useless value assignment in test_create_synth_event() livepatch: Use the default ftrace_ops instead of REGS when ARGS is available ftrace/x86: Allow for arguments to be passed in to ftrace_regs by default ftrace: Have the callbacks receive a struct ftrace_regs instead of pt_regs MAINTAINERS: assign ./fs/tracefs to TRACING tracing: Fix some typos in comments ftrace: Remove unused varible 'ret' ring-buffer: Add recording of ring buffer recursion into recursed_functions ...

Revert: "ring-buffer: Remove HAVE_64BIT_ALIGNED_ACCESS"

2020-12-14T17:33:51Z

It was believed that metag was the only architecture that required the ring buffer to keep 8 byte words aligned on 8 byte architectures, and with its removal, it was assumed that the ring buffer code did not need to handle this case. It appears that sparc64 also requires this. The following was reported on a sparc64 boot up: kernel: futex hash table entries: 65536 (order: 9, 4194304 bytes, linear) kernel: Running postponed tracer tests: kernel: Testing tracer function: kernel: Kernel unaligned access at TPC[552a20] trace_function+0x40/0x140 kernel: Kernel unaligned access at TPC[552a24] trace_function+0x44/0x140 kernel: Kernel unaligned access at TPC[552a20] trace_function+0x40/0x140 kernel: Kernel unaligned access at TPC[552a24] trace_function+0x44/0x140 kernel: Kernel unaligned access at TPC[552a20] trace_function+0x40/0x140 kernel: PASSED Need to put back the 64BIT aligned code for the ring buffer. Link: https://lore.kernel.org/r/CADxRZqzXQRYgKc=y-KV=S_yHL+Y8Ay2mh5ezeZUnpRvg+syWKw@mail.gmail.com Cc: stable@vger.kernel.org Fixes: 86b3de60a0b6 ("ring-buffer: Remove HAVE_64BIT_ALIGNED_ACCESS") Reported-by: Anatoly Pugachev Signed-off-by: Steven Rostedt (VMware)

ring-buffer: Add rb_check_bpage in __rb_allocate_pages

2020-12-14T17:26:32Z

It may be better to check each page is aligned by 4 bytes. The 2 least significant bits of the address will be used as flags. Link: https://lkml.kernel.org/r/20201015113842.2921-1-hqjagain@gmail.com Signed-off-by: Qiujun Huang Signed-off-by: Steven Rostedt (VMware)

ring-buffer: Fix two typos in comments

2020-12-14T17:21:27Z

s/inerrupting/interrupting/ s/beween/between/ Link: https://lkml.kernel.org/r/20201014152749.29986-1-hqjagain@gmail.com Signed-off-by: Qiujun Huang Signed-off-by: Steven Rostedt (VMware)

tracing: Drop unneeded assignment in ring_buffer_resize()

2020-12-14T17:09:54Z

Since commit 0a1754b2a97e ("ring-buffer: Return 0 on success from ring_buffer_resize()"), computing the size is not needed anymore. Drop unneeded assignment in ring_buffer_resize(). Link: https://lkml.kernel.org/r/20201214084503.3079-1-lukas.bulwahn@gmail.com Signed-off-by: Lukas Bulwahn Signed-off-by: Steven Rostedt (VMware)

ring-buffer: Fix a typo in function description

2020-12-07T23:14:53Z

s/ring_buffer_commit_discard/ring_buffer_discard_commit/ Link: https://lkml.kernel.org/r/20201112151800.14382-1-hqjagain@gmail.com Signed-off-by: Qiujun Huang Signed-off-by: Steven Rostedt (VMware)

ring-buffer: Remove obsolete rb_event_is_commit()

2020-12-07T23:08:53Z

Commit a389d86f7fd0 ("ring-buffer: Have nested events still record running time stamp") removed the only uses of rb_event_is_commit() in rb_update_event() and rb_update_write_stamp(). Hence, since then, make CC=clang W=1 warns: kernel/trace/ring_buffer.c:2763:1: warning: unused function 'rb_event_is_commit' [-Wunused-function] Remove this obsolete function. Link: https://lkml.kernel.org/r/20201117053703.11275-1-lukas.bulwahn@gmail.com Reviewed-by: Nathan Chancellor Signed-off-by: Lukas Bulwahn Signed-off-by: Steven Rostedt (VMware)

ring-buffer: Add test to validate the time stamp deltas

2020-12-02T03:00:46Z

While debugging a situation where a delta for an event was calucalted wrong, I realize there was nothing making sure that the delta of events are correct. If a single event has an incorrect delta, then all events after it will also have one. If the discrepency gets large enough, it could cause the time stamps to go backwards when crossing sub buffers, that record a full 64 bit time stamp, and the new deltas are added to that. Add a way to validate the events at most events and when crossing a buffer page. This will help make sure that the deltas are always correct. This test will detect if they are ever corrupted. The test adds a high overhead to the ring buffer recording, as it does the audit for almost every event, and should only be used for testing the ring buffer. This will catch the bug that is fixed by commit 55ea4cf40380 ("ring-buffer: Update write stamp with the correct ts"), which is not applied when this commit is applied. Signed-off-by: Steven Rostedt (VMware)

ring-buffer: Always check to put back before stamp when crossing pages

2020-12-01T04:21:51Z

The current ring buffer logic checks to see if the updating of the event buffer was interrupted, and if it is, it will try to fix up the before stamp with the write stamp to make them equal again. This logic is flawed, because if it is not interrupted, the two are guaranteed to be different, as the current event just updated the before stamp before allocation. This guarantees that the next event (this one or another interrupting one) will think it interrupted the time updates of a previous event and inject an absolute time stamp to compensate. The correct logic is to always update the timestamps when traversing to a new sub buffer. Cc: stable@vger.kernel.org Fixes: a389d86f7fd09 ("ring-buffer: Have nested events still record running time stamp") Signed-off-by: Steven Rostedt (VMware)

ring-buffer: Set the right timestamp in the slow path of __rb_reserve_next()

2020-11-30T20:22:05Z

In the slow path of __rb_reserve_next() a nested event(s) can happen between evaluating the timestamp delta of the current event and updating write_stamp via local_cmpxchg(); in this case the delta is not valid anymore and it should be set to 0 (same timestamp as the interrupting event), since the event that we are currently processing is not the last event in the buffer. Link: https://lkml.kernel.org/r/X8IVJcp1gRE+FJCJ@xps-13-7390 Cc: Ingo Molnar Cc: Masami Hiramatsu Cc: stable@vger.kernel.org Link: https://lwn.net/Articles/831207 Fixes: a389d86f7fd0 ("ring-buffer: Have nested events still record running time stamp") Signed-off-by: Andrea Righi Signed-off-by: Steven Rostedt (VMware)