From: bot+bpf-ci@kernel.org
To: josef@toxicpanda.com,paulmck@kernel.org,frederic@kernel.org,ast@kernel.org,rostedt@goodmis.org
Cc: boqun@kernel.org,mhiramat@kernel.org,mark.rutland@arm.com,peterz@infradead.org,tglx@kernel.org,daniel@iogearbox.net,andrii@kernel.org,puranjay@kernel.org,rcu@vger.kernel.org,bpf@vger.kernel.org,linux-trace-kernel@vger.kernel.org,linux-arm-kernel@lists.infradead.org,linux-kernel@vger.kernel.org,josef@toxicpanda.com,ast@kernel.org,andrii@kernel.org,daniel@iogearbox.net,martin.lau@kernel.org,eddyz87@gmail.com,yonghong.song@linux.dev,mason@kernel.org,ihor.solodrai@linux.dev
Subject: Re: [PATCH v5 06/13] x86/kprobes: Take a Tasks Trace reader in the optprobe template
Date: Tue, 22 Sep 2026 03:22:17 +0000 (UTC) [thread overview]
Message-ID: <ebf2ee78977b3aae08c12e4ba0a18f48463567e20fd282f25acf11f5af375030@mail.kernel.org> (raw)
In-Reply-To: <20260922-b4-rcu-tasks-preempt-qs-v5-6-410f57770bad@toxicpanda.com>
[-- Attachment #1: Type: text/plain, Size: 1585 bytes --]
> x86/kprobes: Take a Tasks Trace reader in the optprobe template
>
> The jump-optimized kprobe template calls optimized_callback() from a
> dynamically allocated slot with preemption enabled, and only Tasks RCU
> keeps that slot alive under a task preempted in the callback. For
> HAVE_RCU_TRAMPOLINE_READERS that means the template must be a Tasks
> Trace reader across the call, so open-code rcu_read_lock_trace() and
> rcu_read_unlock_trace() around it as ftrace_64.S does. The template
> lives in .rodata and is memcpy()d into each slot without relocation
> processing, so the references to current_task and
> rcu_tasks_trace_srcu_struct are absolute (R_X86_64_32S, relocated for
> KASLR like any other) rather than %rip-relative. %rax and %rcx have
> already been saved by SAVE_REGS_STRING and are dead after the call.
>
> The slot itself is dynamically allocated text, so the instructions
> before the lock and after the unlock are covered by the irq-exit check.
> 64-bit only; 32-bit x86 does not take part.
>
> Assisted-by: LLM
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>
This looks like a bug fix for the preemption issue introduced when commit
a19b2e3d7839 removed IRQ disabling from optimized kprobes. Should this
include:
Fixes: a19b2e3d7839 ("kprobes/x86: Remove IRQ disabling from ftrace-based/optimized kprobes")
---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
CI run summary: https://github.com/kernel-patches/bpf/actions/runs/35680506278
next prev parent reply other threads:[~2026-09-22 3:22 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-22 2:23 [PATCH v5 00/13] rcu-tasks: build Tasks RCU on Tasks Trace readers in trampolines Josef Bacik
2026-09-22 2:23 ` [PATCH v5 01/13] entry: Pass pt_regs to irqentry_exit_cond_resched() Josef Bacik
2026-09-22 2:23 ` [PATCH v5 02/13] rcu-tasks: Add a Tasks RCU implementation for reader-marked trampolines Josef Bacik
2026-09-22 9:26 ` Frederic Weisbecker
2026-09-22 2:23 ` [PATCH v5 03/13] kprobes: Expose the optprobe jump window to Tasks RCU Josef Bacik
2026-09-22 3:22 ` bot+bpf-ci
2026-09-22 2:23 ` [PATCH v5 04/13] ftrace: Mark modules hosting direct-call trampolines for " Josef Bacik
2026-09-22 2:23 ` [PATCH v5 05/13] x86/ftrace: Take a Tasks Trace reader around ftrace_caller's call-out Josef Bacik
2026-09-22 2:23 ` [PATCH v5 06/13] x86/kprobes: Take a Tasks Trace reader in the optprobe template Josef Bacik
2026-09-22 3:22 ` bot+bpf-ci [this message]
2026-09-22 2:23 ` [PATCH v5 07/13] bpf, x86: Take a Tasks Trace reader in the trampoline around its call-outs Josef Bacik
2026-09-22 3:22 ` bot+bpf-ci
2026-09-22 2:23 ` [PATCH v5 08/13] arm64: ftrace: Take a Tasks Trace reader around ftrace_caller's call-out Josef Bacik
2026-09-22 2:23 ` [PATCH v5 09/13] bpf, arm64: Take a Tasks Trace reader in the trampoline around its call-outs Josef Bacik
2026-09-22 2:23 ` [PATCH v5 10/13] samples: ftrace: Make the direct-call trampolines Tasks Trace readers Josef Bacik
2026-09-22 3:35 ` bot+bpf-ci
2026-09-22 2:23 ` [PATCH v5 11/13] rcutorture: Make Tasks RCU readers Tasks Trace readers where required Josef Bacik
2026-09-22 2:23 ` [PATCH v5 12/13] rcu-tasks-trace: Assert no reader is held on return to userspace Josef Bacik
2026-09-22 3:11 ` bot+bpf-ci
2026-09-22 2:23 ` [PATCH v5 13/13] x86, arm64: Build Tasks RCU on Tasks Trace readers in trampolines Josef Bacik
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