From 0e5cdb47b4c8f69e5e6ab5bf3d44f79059ffad8a Mon Sep 17 00:00:00 2001 From: Changbin Du Date: Tue, 31 Jan 2023 07:26:59 +0800 Subject: [PATCH] riscv: patch: Fixup lockdep warning in stop_machine The task of ftrace_arch_code_modify(_post)_prepare() caller is stop_machine, whose caller and work thread are of different tasks. The lockdep checker needs the same task context, or it's wrong. That means it's a bug here to use lockdep_assert_held because we don't guarantee the same task context. kernel/locking/lockdep.c: int __lock_is_held(const struct lockdep_map *lock, int read) { struct task_struct *curr = current; int i; for (i = 0; i < curr->lockdep_depth; i++) { ^^^^^^^^^^^^^^^^^^^ struct held_lock *hlock = curr->held_locks + i; ^^^^^^^^^^^^^^^^ if (match_held_lock(hlock, lock)) { if (read == -1 || !!hlock->read == read) return LOCK_STATE_HELD; The __lock_is_held depends on current held_locks records; if stop_machine makes the checker runing on another task, that's wrong. Here is the log: [ 15.761523] ------------[ cut here ]------------ [ 15.762125] WARNING: CPU: 0 PID: 15 at arch/riscv/kernel/patch.c:63 patch_insn_write+0x72/0x364 [ 15.763258] Modules linked in: [ 15.764154] CPU: 0 PID: 15 Comm: migration/0 Not tainted 6.1.0-rc1-00014-g66924be85884-dirty #377 [ 15.765339] Hardware name: riscv-virtio,qemu (DT) [ 15.765985] Stopper: multi_cpu_stop+0x0/0x192 <- stop_cpus.constprop.0+0x90/0xe2 [ 15.766711] epc : patch_insn_write+0x72/0x364 [ 15.767011] ra : patch_insn_write+0x70/0x364 [ 15.767276] epc : ffffffff8000721e ra : ffffffff8000721c sp : ff2000000067bca0 [ 15.767622] gp : ffffffff81603f90 tp : ff60000002432a00 t0 : 7300000000000000 [ 15.767919] t1 : 0000000000000000 t2 : 73695f6b636f6c5f s0 : ff2000000067bcf0 [ 15.768238] s1 : 0000000000000008 a0 : 0000000000000000 a1 : 0000000000000000 [ 15.768537] a2 : 0000000000000000 a3 : 0000000000000000 a4 : 0000000000000000 [ 15.768837] a5 : 0000000000000000 a6 : 0000000000000000 a7 : 0000000000000000 [ 15.769139] s2 : ffffffff80009faa s3 : ff2000000067bd10 s4 : ffffffffffffffff [ 15.769447] s5 : 0000000000000001 s6 : 0000000000000001 s7 : 0000000000000003 [ 15.769740] s8 : 0000000000000002 s9 : 0000000000000004 s10: 0000000000000003 [ 15.770027] s11: 0000000000000002 t3 : 0000000000000000 t4 : ffffffff819af097 [ 15.770323] t5 : ffffffff819af098 t6 : ff2000000067ba28 [ 15.770574] status: 0000000200000100 badaddr: 0000000000000000 cause: 0000000000000003 [ 15.771102] [] patch_text_nosync+0x10/0x3a [ 15.771421] [] ftrace_update_ftrace_func+0x74/0x10a [ 15.771704] [] ftrace_modify_all_code+0xb0/0x16c [ 15.771958] [] __ftrace_modify_code+0x12/0x1c [ 15.772196] [] multi_cpu_stop+0x14a/0x192 [ 15.772454] [] cpu_stopper_thread+0x96/0x14c [ 15.772699] [] smpboot_thread_fn+0xf8/0x1cc [ 15.772945] [] kthread+0xe2/0xf8 [ 15.773160] [] ret_from_exception+0x0/0x14 [ 15.773471] ---[ end trace 0000000000000000 ]--- By the way, this also fixes the same issue for patch_text(). Fixes: 0ff7c3b33127 ("riscv: Use text_mutex instead of patch_lock") Co-developed-by: Guo Ren Signed-off-by: Guo Ren Cc: Zong Li Cc: Palmer Dabbelt Signed-off-by: Changbin Du --- arch/riscv/kernel/patch.c | 7 ------- 1 file changed, 7 deletions(-) diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c index 765004b605132a..8619706f8dfd05 100644 --- a/arch/riscv/kernel/patch.c +++ b/arch/riscv/kernel/patch.c @@ -55,13 +55,6 @@ static int patch_insn_write(void *addr, const void *insn, size_t len) bool across_pages = (((uintptr_t) addr & ~PAGE_MASK) + len) > PAGE_SIZE; int ret; - /* - * Before reaching here, it was expected to lock the text_mutex - * already, so we don't need to give another lock here and could - * ensure that it was safe between each cores. - */ - lockdep_assert_held(&text_mutex); - if (across_pages) patch_map(addr + len, FIX_TEXT_POKE1);