No architectural changes**: Pure bug fix with no API changes or feature additions 6. **Low regression risk**: The new flag-based check is more correct than the mm-based check; any behavioral changes would be fixing incorrect behavior #### **Verification in Current Tree:** I confirmed that linux-autosel-6.17 still has the old buggy code: - Line 7443: Missing PF_USER_WORKER in the check - Line 8083: Still uses `current->mm != NULL` - callchain.c:245: Still uses `if (current->mm)` This confirms the fix is needed and not yet applied. #### **Conclusion:** This is a **clear YES for backporting**. It's a well-understood correctness fix for a real bug affecting perf profiling of io_uring workloads, with minimal risk and part of an ongoing stable backport series. kernel/events/callchain.c | 6 +++--- kernel/events/core.c | 4 ++-- 2 files changed, 5 insertions(+), 5 deletions(-) diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c index 6c83ad674d010..decff7266cfbd 100644 --- a/kernel/events/callchain.c +++ b/kernel/events/callchain.c @@ -242,10 +242,10 @@ get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user, if (user) { if (!user_mode(regs)) { - if (current->mm) - regs = task_pt_regs(current); - else + if (current->flags & (PF_KTHREAD | PF_USER_WORKER)) regs = NULL; + else + regs = task_pt_regs(current); } if (regs) { diff --git a/kernel/events/core.c b/kernel/events/core.c index 820127536e62b..ea9ff856770be 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -7440,7 +7440,7 @@ static void perf_sample_regs_user(struct perf_regs *regs_user, if (user_mode(regs)) { regs_user->abi = perf_reg_abi(current); regs_user->regs = regs; - } else if (!(current->flags & PF_KTHREAD)) { + } else if (!(current->flags & (PF_KTHREAD | PF_USER_WORKER))) { perf_get_regs_user(regs_user, regs); } else { regs_user->abi = PERF_SAMPLE_REGS_ABI_NONE; @@ -8080,7 +8080,7 @@ static u64 perf_virt_to_phys(u64 virt) * Try IRQ-safe get_user_page_fast_only first. * If failed, leave phys_addr as 0. */ - if (current->mm != NULL) { + if (!(current->flags & (PF_KTHREAD | PF_USER_WORKER))) { struct page *p; pagefault_disable(); -- 2.51.0[PATCH AUTOSEL 6.17-6.6] perf: Use current->flags & PF_KTHREAD|PF_USER_WORKER instead of current->mm == NULLSasha Levin undefinedpatches@lists.linux.dev, stable@vger.kernel.org undefined undefined undefined undefined undefined undefined undefined undefined undefined«yƒ„Q