Messages in this thread Patch in this message | | | Date | Thu, 20 Aug 2020 19:20:46 +0200 | From | Marco Elver <> | Subject | Re: [PATCH 0/9] TRACE_IRQFLAGS wreckage |
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On Thu, Aug 20, 2020 at 04:58PM +0200, peterz@infradead.org wrote: > On Thu, Aug 20, 2020 at 10:36:43AM -0400, Steven Rostedt wrote: > > > > I tested this series on top of tip/master and triggered the below > > warning when running the irqsoff tracer boot up test (config attached). > > > > -- Steve > > > > Testing tracer irqsoff: > > > > ============================= > > WARNING: suspicious RCU usage > > 5.9.0-rc1-test+ #92 Not tainted > > ----------------------------- > > include/trace/events/lock.h:13 suspicious rcu_dereference_check() usage! ... > > Shiny, I think that wants something like the below, but let me go frob > my config and test it. > > --- > --- a/drivers/cpuidle/cpuidle.c > +++ b/drivers/cpuidle/cpuidle.c ...
With that applied (manually, due to conflicts), I still get warnings for certain call locations with KCSAN on (that is with my fix from the other email):
| ============================= | WARNING: suspicious RCU usage | 5.9.0-rc1+ #23 Tainted: G W | ----------------------------- | include/trace/events/random.h:310 suspicious rcu_dereference_check() usage! | | other info that might help us debug this: | | | rcu_scheduler_active = 2, debug_locks = 0 | RCU used illegally from extended quiescent state! | no locks held by swapper/1/0. | | stack backtrace: | CPU: 1 PID: 0 Comm: swapper/1 Tainted: G W 5.9.0-rc1+ #23 | Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1 04/01/2014 | Call Trace: | __dump_stack lib/dump_stack.c:77 [inline] | dump_stack+0xf1/0x14d lib/dump_stack.c:118 | trace_prandom_u32 include/trace/events/random.h:310 [inline] | prandom_u32+0x1ee/0x200 lib/random32.c:86 | prandom_u32_max include/linux/prandom.h:46 [inline] | reset_kcsan_skip kernel/kcsan/core.c:277 [inline] | kcsan_setup_watchpoint+0x9b/0x600 kernel/kcsan/core.c:424 | is_idle_task+0xd/0x20 include/linux/sched.h:1671 <==== inline, but not noinstr | irqentry_enter+0x17/0x50 kernel/entry/common.c:293 <==== noinstr function
We can fix that with the patch below.
That leaves me with this, still due to prandom_u32(). :-/
| ------------[ cut here ]------------ | DEBUG_LOCKS_WARN_ON(lockdep_hardirqs_enabled()) | WARNING: CPU: 4 PID: 1861 at kernel/locking/lockdep.c:4875 check_flags.part.0+0x157/0x160 kernel/locking/lockdep.c:4875 | Modules linked in: | CPU: 4 PID: 1861 Comm: kworker/u16:4 Not tainted 5.9.0-rc1+ #24 | Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1 04/01/2014 | RIP: 0010:check_flags.part.0+0x157/0x160 kernel/locking/lockdep.c:4875 | Code: c0 0f 84 70 5d 00 00 44 8b 0d fd 11 5f 06 45 85 c9 0f 85 60 5d 00 00 48 c7 c6 3e d0 f4 86 48 c7 c7 b2 49 f3 86 e8 8d 49 f6 ff <0f> 0b e9 46 5d 00 00 66 90 41 57 41 56 49 89 fe 41 55 41 89 d5 41 | RSP: 0000:ffffc900034bfcb0 EFLAGS: 00010082 | RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff8136161c | RDX: ffff88881a9dcb00 RSI: ffffffff81363835 RDI: 0000000000000006 | RBP: ffffc900034bfd00 R08: 0000000000000000 R09: 0000ffffffffffff | R10: 0000000000000104 R11: 0000ffff874efd6b R12: ffffffff874f26c0 | R13: 0000000000000244 R14: 0000000000000000 R15: 0000000000000046 | FS: 0000000000000000(0000) GS:ffff88881fc00000(0000) knlGS:0000000000000000 | CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 | CR2: 0000000000000000 CR3: 0000000007489001 CR4: 0000000000770ee0 | DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 | DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 | PKRU: 55555554 | Call Trace: | check_flags kernel/locking/lockdep.c:4871 [inline] | lock_is_held_type+0x42/0x100 kernel/locking/lockdep.c:5042 | lock_is_held include/linux/lockdep.h:267 [inline] | rcu_read_lock_sched_held+0x41/0x80 kernel/rcu/update.c:136 | trace_prandom_u32 include/trace/events/random.h:310 [inline] | prandom_u32+0x1bb/0x200 lib/random32.c:86 | prandom_u32_max include/linux/prandom.h:46 [inline] | reset_kcsan_skip kernel/kcsan/core.c:277 [inline] | kcsan_setup_watchpoint+0x9b/0x600 kernel/kcsan/core.c:424 | perf_lock_task_context+0x5e3/0x6e0 kernel/events/core.c:1491 | perf_pin_task_context kernel/events/core.c:1506 [inline] | perf_event_exit_task_context kernel/events/core.c:12284 [inline] | perf_event_exit_task+0x1e2/0x910 kernel/events/core.c:12364 | do_exit+0x70e/0x18b0 kernel/exit.c:815 | call_usermodehelper_exec_async+0x2e2/0x2f0 kernel/umh.c:114 | ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294 | irq event stamp: 107 | hardirqs last enabled at (107): [<ffffffff815532ab>] perf_lock_task_context+0x5db/0x6e0 kernel/events/core.c:1491 | hardirqs last disabled at (106): [<ffffffff81552f12>] perf_lock_task_context+0x242/0x6e0 kernel/events/core.c:1459 | softirqs last enabled at (0): [<ffffffff8129b95e>] copy_process+0xe9e/0x3970 kernel/fork.c:2004 | softirqs last disabled at (0): [<0000000000000000>] 0x0 | ---[ end trace a3058d9b157af5c4 ]--- | possible reason: unannotated irqs-off. | irq event stamp: 107 | hardirqs last enabled at (107): [<ffffffff815532ab>] perf_lock_task_context+0x5db/0x6e0 kernel/events/core.c:1491 | hardirqs last disabled at (106): [<ffffffff81552f12>] perf_lock_task_context+0x242/0x6e0 kernel/events/core.c:1459 | softirqs last enabled at (0): [<ffffffff8129b95e>] copy_process+0xe9e/0x3970 kernel/fork.c:2004 | softirqs last disabled at (0): [<0000000000000000>] 0x0
Suggestions?
Thanks, -- Marco
------ >8 ------
From 4ec9dd472c978e1eba622fb22bc04e4357f10421 Mon Sep 17 00:00:00 2001 From: Marco Elver <elver@google.com> Date: Thu, 20 Aug 2020 19:06:09 +0200 Subject: [PATCH] sched: Turn inline into __always_inline due to noinstr use
is_idle_task() may be used from noinstr functions such as irqentry_enter(). Since the compiler is free to not inline regular inline functions, switch to using __always_inline.
Signed-off-by: Marco Elver <elver@google.com> --- include/linux/sched.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h index 93ecd930efd3..afe01e232935 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1666,7 +1666,7 @@ extern struct task_struct *idle_task(int cpu); * * Return: 1 if @p is an idle task. 0 otherwise. */ -static inline bool is_idle_task(const struct task_struct *p) +static __always_inline bool is_idle_task(const struct task_struct *p) { return !!(p->flags & PF_IDLE); } -- 2.28.0.297.g1956fa8f8d-goog
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