linux/kernel/trace/ring_buffer.c, branch v6.19

ring-buffer: Avoid softlockup in ring_buffer_resize() during memory free

2026-01-07T19:52:22Z

When user resize all trace ring buffer through file 'buffer_size_kb', then in ring_buffer_resize(), kernel allocates buffer pages for each cpu in a loop. If the kernel preemption model is PREEMPT_NONE and there are many cpus and there are many buffer pages to be freed, it may not give up cpu for a long time and finally cause a softlockup. To avoid it, call cond_resched() after each cpu buffer free as Commit f6bd2c92488c ("ring-buffer: Avoid softlockup in ring_buffer_resize()") does. Detailed call trace as follow: rcu: INFO: rcu_sched self-detected stall on CPU rcu: 24-....: (14837 ticks this GP) idle=521c/1/0x4000000000000000 softirq=230597/230597 fqs=5329 rcu: (t=15004 jiffies g=26003221 q=211022 ncpus=96) CPU: 24 UID: 0 PID: 11253 Comm: bash Kdump: loaded Tainted: G EL 6.18.2+ #278 NONE pc : arch_local_irq_restore+0x8/0x20 arch_local_irq_restore+0x8/0x20 (P) free_frozen_page_commit+0x28c/0x3b0 __free_frozen_pages+0x1c0/0x678 ___free_pages+0xc0/0xe0 free_pages+0x3c/0x50 ring_buffer_resize.part.0+0x6a8/0x880 ring_buffer_resize+0x3c/0x58 __tracing_resize_ring_buffer.part.0+0x34/0xd8 tracing_resize_ring_buffer+0x8c/0xd0 tracing_entries_write+0x74/0xd8 vfs_write+0xcc/0x288 ksys_write+0x74/0x118 __arm64_sys_write+0x24/0x38 Cc: Link: https://patch.msgid.link/20251228065008.2396573-1-mawupeng1@huawei.com Signed-off-by: Wupeng Ma Acked-by: Masami Hiramatsu (Google) Signed-off-by: Steven Rostedt (Google)

tracing: Fix multiple typos in ring_buffer.c

2025-12-05T20:43:40Z

Fix multiple typos in comments: "ording" -> "ordering" "scatch" -> "scratch" "wont" -> "won't" Link: https://patch.msgid.link/20251121221835.28032-5-mhi@mailbox.org Signed-off-by: Maurice Hieronymus Signed-off-by: Steven Rostedt (Google)

Merge tag 'trace-ringbuffer-v6.19' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

2025-12-05T18:50:24Z

Pull trace ring-buffer cleanup from Steven Rostedt: - Add helper functions for allocations The allocation of the per CPU buffer descriptor, the buffer page descriptors and the buffer page data itself can be pretty ugly. Add some helper macros and a function to have the code that allocates buffer pages and such look a little cleaner. * tag 'trace-ringbuffer-v6.19' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: ring-buffer: Add helper functions for allocations

ring-buffer: Add helper functions for allocations

2025-12-02T20:49:35Z

The allocation of the per CPU buffer descriptor, the buffer page descriptors and the buffer page data itself can be pretty ugly: kzalloc_node(ALIGN(sizeof(struct buffer_page), cache_line_size()), GFP_KERNEL, cpu_to_node(cpu)); And the data pages: page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_COMP | __GFP_ZERO, order); if (!page) return NULL; bpage->page = page_address(page); rb_init_page(bpage->page); Add helper functions to make the code easier to read. This does make all allocations of the data page (bpage->page) allocated with the __GFP_RETRY_MAYFAIL flag (and not just the bulk allocator). Which is actually better, as allocating the data page for the ring buffer tracing should try hard but not trigger the OOM killer. Link: https://lore.kernel.org/all/CAHk-=wjMMSAaqTjBSfYenfuzE1bMjLj+2DLtLWJuGt07UGCH_Q@mail.gmail.com/ Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Link: https://patch.msgid.link/20251125121153.35c07461@gandalf.local.home Suggested-by: Linus Torvalds Signed-off-by: Steven Rostedt (Google)

ring-buffer: Do not warn in ring_buffer_map_get_reader() when reader catches up

2025-11-07T00:38:54Z

The function ring_buffer_map_get_reader() is a bit more strict than the other get reader functions, and except for certain situations the rb_get_reader_page() should not return NULL. If it does, it triggers a warning. This warning was triggering but after looking at why, it was because another acceptable situation was happening and it wasn't checked for. If the reader catches up to the writer and there's still data to be read on the reader page, then the rb_get_reader_page() will return NULL as there's no new page to get. In this situation, the reader page should not be updated and no warning should trigger. Cc: stable@vger.kernel.org Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Cc: Vincent Donnefort Reported-by: syzbot+92a3745cea5ec6360309@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/690babec.050a0220.baf87.0064.GAE@google.com/ Link: https://lore.kernel.org/20251016132848.1b11bb37@gandalf.local.home Fixes: 117c39200d9d7 ("ring-buffer: Introducing ring-buffer mapping functions") Signed-off-by: Steven Rostedt (Google)

ring buffer: Propagate __rb_map_vma return value to caller

2025-10-09T01:48:58Z

The return value from `__rb_map_vma()`, which rejects writable or executable mappings (VM_WRITE, VM_EXEC, or !VM_MAYSHARE), was being ignored. As a result the caller of `__rb_map_vma` always returned 0 even when the mapping had actually failed, allowing it to proceed with an invalid VMA. Cc: stable@vger.kernel.org Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Link: https://lore.kernel.org/20251008172516.20697-1-ankitkhushwaha.linux@gmail.com Fixes: 117c39200d9d7 ("ring-buffer: Introducing ring-buffer mapping functions") Reported-by: syzbot+ddc001b92c083dbf2b97@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?id=194151be8eaebd826005329b2e123aecae714bdb Signed-off-by: Ankit Khushwaha Signed-off-by: Steven Rostedt (Google)

ring-buffer: Remove redundant semicolons

2025-08-20T13:20:30Z

Remove unnecessary semicolons. Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Link: https://lore.kernel.org/20250813095114.559530-1-liaoyuanhong@vivo.com Signed-off-by: Liao Yuanhong Signed-off-by: Steven Rostedt (Google)

Merge tag 'trace-v6.17-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

2025-08-03T22:03:04Z

Pull more tracing updates from Steven Rostedt: - Remove unneeded goto out statements Over time, the logic was restructured but left a "goto out" where the out label simply did a "return ret;". Instead of jumping to this out label, simply return immediately and remove the out label. - Add guard(ring_buffer_nest) Some calls to the tracing ring buffer can happen when the ring buffer is already being written to at the same context (for example, a trace_printk() in between a ring_buffer_lock_reserve() and a ring_buffer_unlock_commit()). In order to not trigger the recursion detection, these functions use ring_buffer_nest_start() and ring_buffer_nest_end(). Create a guard() for these functions so that their use cases can be simplified and not need to use goto for the release. - Clean up the tracing code with guard() and __free() logic There were several locations that were prime candidates for using guard() and __free() helpers. Switch them over to use them. - Fix output of function argument traces for unsigned int values The function tracer with "func-args" option set will record up to 6 argument registers and then use BTF to format them for human consumption when the trace file is read. There are several arguments that are "unsigned long" and even "unsigned int" that are either and address or a mask. It is easier to understand if they were printed using hexadecimal instead of decimal. The old method just printed all non-pointer values as signed integers, which made it even worse for unsigned integers. For instance, instead of: __local_bh_disable_ip(ip=-2127311112, cnt=256) <-handle_softirqs show: __local_bh_disable_ip(ip=0xffffffff8133cef8, cnt=0x100) <-handle_softirqs" * tag 'trace-v6.17-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: tracing: Have unsigned int function args displayed as hexadecimal ring-buffer: Convert ring_buffer_write() to use guard(preempt_notrace) tracing: Use __free(kfree) in trace.c to remove gotos tracing: Add guard() around locks and mutexes in trace.c tracing: Add guard(ring_buffer_nest) tracing: Remove unneeded goto out logic

ring-buffer: Convert ring_buffer_write() to use guard(preempt_notrace)

2025-08-01T20:49:15Z

The function ring_buffer_write() has a goto out to only do a preempt_enable_notrace(). This can be replaced by a guard. Cc: Masami Hiramatsu Cc: Mark Rutland Cc: Mathieu Desnoyers Cc: Andrew Morton Link: https://lore.kernel.org/20250801203858.205479143@kernel.org Signed-off-by: Steven Rostedt (Google)

ring-buffer: Make the const read-only 'type' static

2025-07-29T19:08:57Z

Don't populate the read-only 'type' on the stack at run time, instead make it static. Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Link: https://lore.kernel.org/20250714160858.1234719-1-colin.i.king@gmail.com Signed-off-by: Colin Ian King Signed-off-by: Steven Rostedt (Google)