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McKenney" , Guenter Roeck References: <20241003181629.36209057@gandalf.local.home> <20241203155542.462b1b21@gandalf.local.home> <20241203220153.3f81f12b@gandalf.local.home> Content-Language: en-US From: Madhavan Srinivasan In-Reply-To: <20241203220153.3f81f12b@gandalf.local.home> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: o04zhgZjbHsTW8kusHOZJFA4pxD-_NVG X-Proofpoint-ORIG-GUID: o04zhgZjbHsTW8kusHOZJFA4pxD-_NVG X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1051,Hydra:6.0.680,FMLib:17.12.62.30 definitions=2024-10-15_01,2024-10-11_01,2024-09-30_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 priorityscore=1501 clxscore=1011 phishscore=0 malwarescore=0 suspectscore=0 mlxscore=0 bulkscore=0 mlxlogscore=999 adultscore=0 lowpriorityscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2411120000 definitions=main-2412050066 On 12/4/24 8:31 AM, Steven Rostedt wrote: > On Tue, 3 Dec 2024 17:48:33 -0800 > Guenter Roeck wrote: > >> Hmm. If you say so. Note that powerpc has the same or a similar problem. >> >> [ 0.142039][ T0] RCU not watching for tracepoint >> [ 0.142488][ T0] >> [ 0.142659][ T0] ============================= >> [ 0.142755][ T0] WARNING: suspicious RCU usage >> [ 0.142914][ T0] 6.13.0-rc1-00058-ge75ce84aa5d3 #1 Not tainted >> [ 0.143082][ T0] ----------------------------- >> [ 0.143178][ T0] kernel/notifier.c:586 notify_die called but RCU thinks we're quiescent! >> >> >> [ 0.152733][ T0] RCU not watching for tracepoint >> [ 0.152770][ T0] >> [ 0.152995][ T0] ============================= >> [ 0.153092][ T0] WARNING: suspicious RCU usage >> [ 0.153187][ T0] 6.13.0-rc1-00058-ge75ce84aa5d3 #1 Not tainted >> [ 0.153301][ T0] ----------------------------- >> [ 0.153394][ T0] include/linux/rcupdate.h:850 rcu_read_lock() used illegally while idle! >> >> [ 0.165396][ T0] RCU not watching for tracepoint >> [ 0.165540][ T0] >> [ 0.165712][ T0] ============================= >> [ 0.165811][ T0] WARNING: suspicious RCU usage >> [ 0.165909][ T0] 6.13.0-rc1-00058-ge75ce84aa5d3 #1 Not tainted >> [ 0.166026][ T0] ----------------------------- >> [ 0.166122][ T0] include/linux/rcupdate.h:878 rcu_read_unlock() used illegally while idle! >> >> and many more. > > Grumble. It's just that one file. I wonder if we could just do a hack like > this? > Below patch fixes the issue in powerpc Tested-by: Madhavan Srinivasan Thanks maddy > Paul? > > diff --git a/kernel/trace/trace_preemptirq.c b/kernel/trace/trace_preemptirq.c > index 5c03633316a6..58098873efa9 100644 > --- a/kernel/trace/trace_preemptirq.c > +++ b/kernel/trace/trace_preemptirq.c > @@ -10,11 +10,42 @@ > #include > #include > #include > +#include > #include "trace.h" > > #define CREATE_TRACE_POINTS > #include > > +/* > + * Use regular trace points on architectures that implement noinstr > + * tooling: these calls will only happen with RCU enabled, which can > + * use a regular tracepoint. > + * > + * On older architectures, RCU may not be watching in idle. In that > + * case, wake up RCU to watch while calling the tracepoint. These > + * aren't NMI-safe - so exclude NMI contexts: > + */ > +#ifdef CONFIG_ARCH_WANTS_NO_INSTR > +#define trace(point, args) trace_##point(args) > +#else > +#define trace(point, args) \ > + do { \ > + if (trace_##point##_enabled()) { \ > + bool exit_rcu = false; \ > + if (in_nmi()) \ > + break; \ > + if (!IS_ENABLED(CONFIG_TINY_RCU) && \ > + is_idle_task(current)) { \ > + ct_irq_enter(); \ > + exit_rcu = true; \ > + } \ > + trace_##point(args); \ > + if (exit_rcu) \ > + ct_irq_exit(); \ > + } \ > + } while (0) > +#endif > + > #ifdef CONFIG_TRACE_IRQFLAGS > /* Per-cpu variable to prevent redundant calls when IRQs already off */ > static DEFINE_PER_CPU(int, tracing_irq_cpu); > @@ -28,7 +59,7 @@ static DEFINE_PER_CPU(int, tracing_irq_cpu); > void trace_hardirqs_on_prepare(void) > { > if (this_cpu_read(tracing_irq_cpu)) { > - trace_irq_enable(CALLER_ADDR0, CALLER_ADDR1); > + trace(irq_enable, TP_ARGS(CALLER_ADDR0, CALLER_ADDR1)); > tracer_hardirqs_on(CALLER_ADDR0, CALLER_ADDR1); > this_cpu_write(tracing_irq_cpu, 0); > } > @@ -39,7 +70,7 @@ NOKPROBE_SYMBOL(trace_hardirqs_on_prepare); > void trace_hardirqs_on(void) > { > if (this_cpu_read(tracing_irq_cpu)) { > - trace_irq_enable(CALLER_ADDR0, CALLER_ADDR1); > + trace(irq_enable, TP_ARGS(CALLER_ADDR0, CALLER_ADDR1)); > tracer_hardirqs_on(CALLER_ADDR0, CALLER_ADDR1); > this_cpu_write(tracing_irq_cpu, 0); > } > @@ -61,7 +92,7 @@ void trace_hardirqs_off_finish(void) > if (!this_cpu_read(tracing_irq_cpu)) { > this_cpu_write(tracing_irq_cpu, 1); > tracer_hardirqs_off(CALLER_ADDR0, CALLER_ADDR1); > - trace_irq_disable(CALLER_ADDR0, CALLER_ADDR1); > + trace(irq_disable, TP_ARGS(CALLER_ADDR0, CALLER_ADDR1)); > } > > } > @@ -75,7 +106,7 @@ void trace_hardirqs_off(void) > if (!this_cpu_read(tracing_irq_cpu)) { > this_cpu_write(tracing_irq_cpu, 1); > tracer_hardirqs_off(CALLER_ADDR0, CALLER_ADDR1); > - trace_irq_disable(CALLER_ADDR0, CALLER_ADDR1); > + trace(irq_disable, TP_ARGS(CALLER_ADDR0, CALLER_ADDR1)); > } > } > EXPORT_SYMBOL(trace_hardirqs_off); > @@ -86,13 +117,13 @@ NOKPROBE_SYMBOL(trace_hardirqs_off); > > void trace_preempt_on(unsigned long a0, unsigned long a1) > { > - trace_preempt_enable(a0, a1); > + trace(preempt_enable, TP_ARGS(a0, a1)); > tracer_preempt_on(a0, a1); > } > > void trace_preempt_off(unsigned long a0, unsigned long a1) > { > - trace_preempt_disable(a0, a1); > + trace(preempt_disable, TP_ARGS(a0, a1)); > tracer_preempt_off(a0, a1); > } > #endif > > > I tested this by forcing x86 to use this code, and it appeared to work. > > -- Steve > >