[BUG] msr-trace.h:42 suspicious rcu_dereference_check() usage!

[Jiri Olsa]

hi,
Jan hit following output when msr tracepoints are enabled on amd server:

[   91.585653] ===============================
[   91.589840] [ INFO: suspicious RCU usage. ]
[   91.594025] 4.9.0-rc1+ #1 Not tainted
[   91.597691] -------------------------------
[   91.601877] ./arch/x86/include/asm/msr-trace.h:42 suspicious 
rcu_dereference_check() usage!
[   91.610222] 
[   91.610222] other info that might help us debug this:
[   91.610222] 
[   91.618224] 
[   91.618224] RCU used illegally from idle CPU!
[   91.618224] rcu_scheduler_active = 1, debug_locks = 0
[   91.629081] RCU used illegally from extended quiescent state!
[   91.634820] no locks held by swapper/1/0.
[   91.638832] 
[   91.638832] stack backtrace:
[   91.643192] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.9.0-rc1+ #1
[   91.649457] Hardware name: empty empty/S3992, BIOS 'V2.03   ' 05/09/2008
[   91.656159]  ffffc900018fbdf8 ffffffff813ed43c ffff88017ede8000 
0000000000000001
[   91.663637]  ffffc900018fbe28 ffffffff810fdcd7 ffff880233f95dd0 
00000000c0010055
[   91.671107]  0000000000000000 0000000000000000 ffffc900018fbe58 
ffffffff814297ac
[   91.678560] Call Trace:
[   91.681022]  [<ffffffff813ed43c>] dump_stack+0x85/0xc9
[   91.686164]  [<ffffffff810fdcd7>] lockdep_rcu_suspicious+0xe7/0x120
[   91.692429]  [<ffffffff814297ac>] do_trace_read_msr+0x14c/0x1b0
[   91.698349]  [<ffffffff8106ddb2>] native_read_msr+0x32/0x40
[   91.703921]  [<ffffffff8103b2be>] amd_e400_idle+0x7e/0x110
[   91.709407]  [<ffffffff8103b78f>] arch_cpu_idle+0xf/0x20
[   91.714720]  [<ffffffff8181cd33>] default_idle_call+0x23/0x40
[   91.720467]  [<ffffffff810f306a>] cpu_startup_entry+0x1da/0x2b0
[   91.726387]  [<ffffffff81058b1f>] start_secondary+0x17f/0x1f0


it got away with attached change.. but this rcu logic
is far beyond me, so it's just wild guess.. ;-)

thanks,
jirka


---
diff --git a/arch/x86/lib/msr.c b/arch/x86/lib/msr.c
index d1dee753b949..ca15becea3b6 100644
--- a/arch/x86/lib/msr.c
+++ b/arch/x86/lib/msr.c
@@ -115,14 +115,14 @@ int msr_clear_bit(u32 msr, u8 bit)
 #ifdef CONFIG_TRACEPOINTS
 void do_trace_write_msr(unsigned msr, u64 val, int failed)
 {
-       trace_write_msr(msr, val, failed);
+       trace_write_msr_rcuidle(msr, val, failed);
 }
 EXPORT_SYMBOL(do_trace_write_msr);
 EXPORT_TRACEPOINT_SYMBOL(write_msr);
 
 void do_trace_read_msr(unsigned msr, u64 val, int failed)
 {
-       trace_read_msr(msr, val, failed);
+       trace_read_msr_rcuidle(msr, val, failed);
 }
 EXPORT_SYMBOL(do_trace_read_msr);
 EXPORT_TRACEPOINT_SYMBOL(read_msr);