[PATCH] tracing/timerlat: Move hrtimer_init to timerlat_fd open()

[PATCH] tracing/timerlat: Move hrtimer_init to timerlat_fd open()

[Daniel Bristot de Oliveira]

Currently, the timerlat's hrtimer is initialized at the first read of
timerlat_fd, and destroyed at close(). It works, but it causes an error
if the user program open() and close() the file without reading.

Move hrtimer_init to timerlat_fd open() to avoid this problem.

No functional changes.

Fixes: e88ed227f639 ("tracing/timerlat: Add user-space interface")
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
---
 kernel/trace/trace_osnoise.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
index bd0d01d00fb9..a8e28f9b9271 100644
--- a/kernel/trace/trace_osnoise.c
+++ b/kernel/trace/trace_osnoise.c
@@ -2444,6 +2444,9 @@ static int timerlat_fd_open(struct inode *inode, struct file *file)
 	tlat = this_cpu_tmr_var();
 	tlat->count = 0;
 
+	hrtimer_init(&tlat->timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED_HARD);
+	tlat->timer.function = timerlat_irq;
+
 	migrate_enable();
 	return 0;
 };
@@ -2526,9 +2529,6 @@ timerlat_fd_read(struct file *file, char __user *ubuf, size_t count,
 		tlat->tracing_thread = false;
 		tlat->kthread = current;
 
-		hrtimer_init(&tlat->timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED_HARD);
-		tlat->timer.function = timerlat_irq;
-
 		/* Annotate now to drift new period */
 		tlat->abs_period = hrtimer_cb_get_time(&tlat->timer);
 
-- 
2.43.0

Re: [PATCH] tracing/timerlat: Move hrtimer_init to timerlat_fd open()

[Steven Rostedt]

On Thu,  1 Feb 2024 16:13:39 +0100
Daniel Bristot de Oliveira <bristot@kernel.org> wrote:

> Currently, the timerlat's hrtimer is initialized at the first read of
> timerlat_fd, and destroyed at close(). It works, but it causes an error
> if the user program open() and close() the file without reading.
> 
> Move hrtimer_init to timerlat_fd open() to avoid this problem.
> 
> No functional changes.

It can't be fixing something and not have any functional changes.

No functional changes means the code is restructured but the resulting
assembly would be the same.

Like moving functions around in a file so that you don't need extra
prototype declarations.

Please only add "No functional changes" if the function's assembly would be
the same.

> 
> Fixes: e88ed227f639 ("tracing/timerlat: Add user-space interface")

With a fixes tag, I'm assuming his should go into v6.8 with a Cc stable?

-- Steve


> Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
> ---
>  kernel/trace/trace_osnoise.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
> index bd0d01d00fb9..a8e28f9b9271 100644
> --- a/kernel/trace/trace_osnoise.c
> +++ b/kernel/trace/trace_osnoise.c
> @@ -2444,6 +2444,9 @@ static int timerlat_fd_open(struct inode *inode, struct file *file)
>  	tlat = this_cpu_tmr_var();
>  	tlat->count = 0;
>  
> +	hrtimer_init(&tlat->timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED_HARD);
> +	tlat->timer.function = timerlat_irq;
> +
>  	migrate_enable();
>  	return 0;
>  };
> @@ -2526,9 +2529,6 @@ timerlat_fd_read(struct file *file, char __user *ubuf, size_t count,
>  		tlat->tracing_thread = false;
>  		tlat->kthread = current;
>  
> -		hrtimer_init(&tlat->timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED_HARD);
> -		tlat->timer.function = timerlat_irq;
> -
>  		/* Annotate now to drift new period */
>  		tlat->abs_period = hrtimer_cb_get_time(&tlat->timer);
>  

Re: [PATCH] tracing/timerlat: Move hrtimer_init to timerlat_fd open()

[Daniel Bristot de Oliveira]

On 2/1/24 16:25, Steven Rostedt wrote:
> On Thu,  1 Feb 2024 16:13:39 +0100
> Daniel Bristot de Oliveira <bristot@kernel.org> wrote:
> 
>> Currently, the timerlat's hrtimer is initialized at the first read of
>> timerlat_fd, and destroyed at close(). It works, but it causes an error
>> if the user program open() and close() the file without reading.
>>
>> Move hrtimer_init to timerlat_fd open() to avoid this problem.
>>
>> No functional changes.
> 
> It can't be fixing something and not have any functional changes.
> 
> No functional changes means the code is restructured but the resulting
> assembly would be the same.
> 
> Like moving functions around in a file so that you don't need extra
> prototype declarations.
> 
> Please only add "No functional changes" if the function's assembly would be
> the same.

ok

>>
>> Fixes: e88ed227f639 ("tracing/timerlat: Add user-space interface")
> 
> With a fixes tag, I'm assuming his should go into v6.8 with a Cc stable?

right, I added it on Cc, but did not include the Cc:.. tag. It seems that I should have.

-- Daniel

> -- Steve
> 
> 
>> Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
>> ---
>>  kernel/trace/trace_osnoise.c | 6 +++---
>>  1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
>> index bd0d01d00fb9..a8e28f9b9271 100644
>> --- a/kernel/trace/trace_osnoise.c
>> +++ b/kernel/trace/trace_osnoise.c
>> @@ -2444,6 +2444,9 @@ static int timerlat_fd_open(struct inode *inode, struct file *file)
>>  	tlat = this_cpu_tmr_var();
>>  	tlat->count = 0;
>>  
>> +	hrtimer_init(&tlat->timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED_HARD);
>> +	tlat->timer.function = timerlat_irq;
>> +
>>  	migrate_enable();
>>  	return 0;
>>  };
>> @@ -2526,9 +2529,6 @@ timerlat_fd_read(struct file *file, char __user *ubuf, size_t count,
>>  		tlat->tracing_thread = false;
>>  		tlat->kthread = current;
>>  
>> -		hrtimer_init(&tlat->timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED_HARD);
>> -		tlat->timer.function = timerlat_irq;
>> -
>>  		/* Annotate now to drift new period */
>>  		tlat->abs_period = hrtimer_cb_get_time(&tlat->timer);
>>  
> 

Re: [PATCH] tracing/timerlat: Move hrtimer_init to timerlat_fd open()

[Greg KH]

On Thu, Feb 01, 2024 at 04:13:39PM +0100, Daniel Bristot de Oliveira wrote:
> Currently, the timerlat's hrtimer is initialized at the first read of
> timerlat_fd, and destroyed at close(). It works, but it causes an error
> if the user program open() and close() the file without reading.

What error exactly happens?  Userspace, or the kernel crashes?

thanks,

greg k-h

Re: [PATCH] tracing/timerlat: Move hrtimer_init to timerlat_fd open()

[Daniel Bristot de Oliveira]

On 2/1/24 16:44, Greg KH wrote:
> On Thu, Feb 01, 2024 at 04:13:39PM +0100, Daniel Bristot de Oliveira wrote:
>> Currently, the timerlat's hrtimer is initialized at the first read of
>> timerlat_fd, and destroyed at close(). It works, but it causes an error
>> if the user program open() and close() the file without reading.
> 
> What error exactly happens?  Userspace, or the kernel crashes?

sorry, kernel crash:

# echo NO_OSNOISE_WORKLOAD > /sys/kernel/debug/tracing/osnoise/options
# echo timerlat > /sys/kernel/debug/tracing/current_tracer

# cat ./timerlat_load.py
#!/usr/bin/env python3

timerlat_fd = open("/sys/kernel/tracing/osnoise/per_cpu/cpu0/timerlat_fd", 'r')
timerlat_fd.close();

# ./taskset -c 0 ./timerlat_load.py
<BOOM>

[ 6401.611374] BUG: kernel NULL pointer dereference, address: 0000000000000010
[ 6401.611786] #PF: supervisor read access in kernel mode
[ 6401.612081] #PF: error_code(0x0000) - not-present page
[ 6401.612376] PGD 0 P4D 0
[ 6401.612495] Oops: 0000 [#1] PREEMPT SMP NOPTI
[ 6401.612690] CPU: 1 PID: 2673 Comm: python3 Not tainted 6.6.13-200.fc39.x86_64 #1
[ 6401.613011] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-1.fc39 04/01/2014
[ 6401.613379] RIP: 0010:hrtimer_active+0xd/0x50
[ 6401.613577] Code: 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 0f 1f 44 00 00 48 8b 57 30 <8b> 42 10 a8 01 74 09 f3 90 8b 42 10 a8 01 75 f7 80 7f 38 00 75 1d
[ 6401.614374] RSP: 0018:ffffb031009b7e10 EFLAGS: 00010286
[ 6401.614604] RAX: 000000000002db00 RBX: ffff9118f786db08 RCX: 0000000000000000
[ 6401.614914] RDX: 0000000000000000 RSI: ffff9117a0e64400 RDI: ffff9118f786db08
[ 6401.615225] RBP: ffff9118f786db80 R08: ffff9117a0ddd420 R09: ffff9117804d4f70
[ 6401.615534] R10: 0000000000000000 R11: 0000000000000000 R12: ffff9118f786db08
[ 6401.615846] R13: ffff91178fdd5e20 R14: ffff9117840978c0 R15: 0000000000000000
[ 6401.616157] FS:  00007f2ffbab1740(0000) GS:ffff9118f7840000(0000) knlGS:0000000000000000
[ 6401.616508] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 6401.616765] CR2: 0000000000000010 CR3: 00000001b402e000 CR4: 0000000000750ee0
[ 6401.617075] PKRU: 55555554
[ 6401.617197] Call Trace:
[ 6401.617309]  <TASK>
[ 6401.617407]  ? __die+0x23/0x70
[ 6401.617548]  ? page_fault_oops+0x171/0x4e0
[ 6401.617983]  ? srso_alias_return_thunk+0x5/0x7f
[ 6401.618389]  ? avc_has_extended_perms+0x237/0x520
[ 6401.618800]  ? exc_page_fault+0x7f/0x180
[ 6401.619176]  ? asm_exc_page_fault+0x26/0x30
[ 6401.619563]  ? hrtimer_active+0xd/0x50
[ 6401.619926]  hrtimer_cancel+0x15/0x40
[ 6401.620286]  timerlat_fd_release+0x48/0xe0
[ 6401.620666]  __fput+0xf5/0x290
[ 6401.621004]  __x64_sys_close+0x3d/0x80
[ 6401.621370]  do_syscall_64+0x60/0x90
[ 6401.621730]  ? srso_alias_return_thunk+0x5/0x7f
[ 6401.622129]  ? __x64_sys_ioctl+0x72/0xd0
[ 6401.622503]  ? srso_alias_return_thunk+0x5/0x7f
[ 6401.622902]  ? syscall_exit_to_user_mode+0x2b/0x40
[ 6401.623309]  ? srso_alias_return_thunk+0x5/0x7f
[ 6401.623703]  ? do_syscall_64+0x6c/0x90
[ 6401.624063]  ? srso_alias_return_thunk+0x5/0x7f
[ 6401.624457]  ? exit_to_user_mode_prepare+0x142/0x1f0
[ 6401.624868]  ? srso_alias_return_thunk+0x5/0x7f
[ 6401.625262]  ? syscall_exit_to_user_mode+0x2b/0x40
[ 6401.625663]  ? srso_alias_return_thunk+0x5/0x7f
[ 6401.626051]  ? do_syscall_64+0x6c/0x90
[ 6401.626404]  entry_SYSCALL_64_after_hwframe+0x6e/0xd8
[ 6401.626810] RIP: 0033:0x7f2ffb321594
[ 6401.627164] Code: 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 80 3d d5 cd 0d 00 00 74 13 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 3c c3 0f 1f 00 55 48 89 e5 48 83 ec 10 89 7d
[ 6401.628345] RSP: 002b:00007ffe8d8eef18 EFLAGS: 00000202 ORIG_RAX: 0000000000000003
[ 6401.628867] RAX: ffffffffffffffda RBX: 00007f2ffba4e668 RCX: 00007f2ffb321594
[ 6401.629372] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
[ 6401.629879] RBP: 00007ffe8d8eef40 R08: 0000000000000000 R09: 0000000000000000
[ 6401.630384] R10: 55c926e3167eae79 R11: 0000000000000202 R12: 0000000000000003
[ 6401.630889] R13: 00007ffe8d8ef030 R14: 0000000000000000 R15: 00007f2ffba4e668
[ 6401.631394]  </TASK>
[ 6401.631691] Modules linked in: tls nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 rfkill ip_set nf_tables nfnetlink qrtr sunrpc pktcdvd intel_rapl_msr snd_hda_codec_generic intel_rapl_common ledtrig_audio snd_hda_intel snd_intel_dspcfg snd_intel_sdw_acpi snd_hda_codec snd_hda_core snd_hwdep snd_pcm kvm_amd iTCO_wdt snd_timer intel_pmc_bxt ccp joydev iTCO_vendor_support kvm irqbypass i2c_i801 snd i2c_smbus soundcore lpc_ich virtio_balloon loop zram crct10dif_pclmul crc32_pclmul crc32c_intel polyval_clmulni polyval_generic ghash_clmulni_intel sha512_ssse3 sha256_ssse3 sha1_ssse3 virtio_net virtio_gpu virtio_console virtio_blk net_failover failover virtio_dma_buf serio_raw scsi_dh_rdac scsi_dh_emc scsi_dh_alua fuse dm_multipath qemu_fw_cfg
[ 6401.636126] CR2: 0000000000000010
[ 6401.636482] ---[ end trace 0000000000000000 ]---
[ 6401.636891] RIP: 0010:hrtimer_active+0xd/0x50
[ 6401.637288] Code: 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 0f 1f 44 00 00 48 8b 57 30 <8b> 42 10 a8 01 74 09 f3 90 8b 42 10 a8 01 75 f7 80 7f 38 00 75 1d
[ 6401.638507] RSP: 0018:ffffb031009b7e10 EFLAGS: 00010286
[ 6401.638951] RAX: 000000000002db00 RBX: ffff9118f786db08 RCX: 0000000000000000
[ 6401.639478] RDX: 0000000000000000 RSI: ffff9117a0e64400 RDI: ffff9118f786db08
[ 6401.640005] RBP: ffff9118f786db80 R08: ffff9117a0ddd420 R09: ffff9117804d4f70
[ 6401.640535] R10: 0000000000000000 R11: 0000000000000000 R12: ffff9118f786db08
[ 6401.641067] R13: ffff91178fdd5e20 R14: ffff9117840978c0 R15: 0000000000000000
[ 6401.641601] FS:  00007f2ffbab1740(0000) GS:ffff9118f7840000(0000) knlGS:0000000000000000
[ 6401.642174] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 6401.642653] CR2: 0000000000000010 CR3: 00000001b402e000 CR4: 0000000000750ee0
[ 6401.643193] PKRU: 55555554
[ 6401.643548] note: python3[2673] exited with irqs disabled

-- Daniel

> thanks,
> 
> greg k-h

Re: [PATCH] tracing/timerlat: Move hrtimer_init to timerlat_fd open()

[Steven Rostedt]

On Thu, 1 Feb 2024 17:02:56 +0100
Daniel Bristot de Oliveira <bristot@kernel.org> wrote:

> On 2/1/24 16:44, Greg KH wrote:
> > On Thu, Feb 01, 2024 at 04:13:39PM +0100, Daniel Bristot de Oliveira wrote:  
> >> Currently, the timerlat's hrtimer is initialized at the first read of
> >> timerlat_fd, and destroyed at close(). It works, but it causes an error
> >> if the user program open() and close() the file without reading.  
> > 
> > What error exactly happens?  Userspace, or the kernel crashes?  
> 
> sorry, kernel crash:
> 
> # echo NO_OSNOISE_WORKLOAD > /sys/kernel/debug/tracing/osnoise/options
> # echo timerlat > /sys/kernel/debug/tracing/current_tracer
> 
> # cat ./timerlat_load.py
> #!/usr/bin/env python3
> 
> timerlat_fd = open("/sys/kernel/tracing/osnoise/per_cpu/cpu0/timerlat_fd", 'r')
> timerlat_fd.close();
> 
> # ./taskset -c 0 ./timerlat_load.py
> <BOOM>
> 
> [ 6401.611374] BUG: kernel NULL pointer dereference, address: 0000000000000010
> [ 6401.611786] #PF: supervisor read access in kernel mode
> [ 6401.612081] #PF: error_code(0x0000) - not-present page
> [ 6401.612376] PGD 0 P4D 0
> [ 6401.612495] Oops: 0000 [#1] PREEMPT SMP NOPTI
> [ 6401.612690] CPU: 1 PID: 2673 Comm: python3 Not tainted 6.6.13-200.fc39.x86_64 #1
> [ 6401.613011] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-1.fc39 04/01/2014
> [ 6401.613379] RIP: 0010:hrtimer_active+0xd/0x50
> [ 6401.613577] Code: 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 0f 1f 44 00 00 48 8b 57 30 <8b> 42 10 a8 01 74 09 f3 90 8b 42 10 a8 01 75 f7 80 7f 38 00 75 1d
> [ 6401.614374] RSP: 0018:ffffb031009b7e10 EFLAGS: 00010286
> [ 6401.614604] RAX: 000000000002db00 RBX: ffff9118f786db08 RCX: 0000000000000000
> [ 6401.614914] RDX: 0000000000000000 RSI: ffff9117a0e64400 RDI: ffff9118f786db08
> [ 6401.615225] RBP: ffff9118f786db80 R08: ffff9117a0ddd420 R09: ffff9117804d4f70
> [ 6401.615534] R10: 0000000000000000 R11: 0000000000000000 R12: ffff9118f786db08
> [ 6401.615846] R13: ffff91178fdd5e20 R14: ffff9117840978c0 R15: 0000000000000000
> [ 6401.616157] FS:  00007f2ffbab1740(0000) GS:ffff9118f7840000(0000) knlGS:0000000000000000
> [ 6401.616508] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 6401.616765] CR2: 0000000000000010 CR3: 00000001b402e000 CR4: 0000000000750ee0
> [ 6401.617075] PKRU: 55555554
> [ 6401.617197] Call Trace:
> [ 6401.617309]  <TASK>
> [ 6401.617407]  ? __die+0x23/0x70
> [ 6401.617548]  ? page_fault_oops+0x171/0x4e0
> [ 6401.617983]  ? srso_alias_return_thunk+0x5/0x7f
> [ 6401.618389]  ? avc_has_extended_perms+0x237/0x520
> [ 6401.618800]  ? exc_page_fault+0x7f/0x180
> [ 6401.619176]  ? asm_exc_page_fault+0x26/0x30
> [ 6401.619563]  ? hrtimer_active+0xd/0x50
> [ 6401.619926]  hrtimer_cancel+0x15/0x40
> [ 6401.620286]  timerlat_fd_release+0x48/0xe0
> [ 6401.620666]  __fput+0xf5/0x290
> [ 6401.621004]  __x64_sys_close+0x3d/0x80
> [ 6401.621370]  do_syscall_64+0x60/0x90
> [ 6401.621730]  ? srso_alias_return_thunk+0x5/0x7f
> [ 6401.622129]  ? __x64_sys_ioctl+0x72/0xd0
> [ 6401.622503]  ? srso_alias_return_thunk+0x5/0x7f
> [ 6401.622902]  ? syscall_exit_to_user_mode+0x2b/0x40
> [ 6401.623309]  ? srso_alias_return_thunk+0x5/0x7f
> [ 6401.623703]  ? do_syscall_64+0x6c/0x90
> [ 6401.624063]  ? srso_alias_return_thunk+0x5/0x7f
> [ 6401.624457]  ? exit_to_user_mode_prepare+0x142/0x1f0
> [ 6401.624868]  ? srso_alias_return_thunk+0x5/0x7f
> [ 6401.625262]  ? syscall_exit_to_user_mode+0x2b/0x40
> [ 6401.625663]  ? srso_alias_return_thunk+0x5/0x7f
> [ 6401.626051]  ? do_syscall_64+0x6c/0x90
> [ 6401.626404]  entry_SYSCALL_64_after_hwframe+0x6e/0xd8
> [ 6401.626810] RIP: 0033:0x7f2ffb321594
> [ 6401.627164] Code: 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 80 3d d5 cd 0d 00 00 74 13 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 3c c3 0f 1f 00 55 48 89 e5 48 83 ec 10 89 7d
> [ 6401.628345] RSP: 002b:00007ffe8d8eef18 EFLAGS: 00000202 ORIG_RAX: 0000000000000003
> [ 6401.628867] RAX: ffffffffffffffda RBX: 00007f2ffba4e668 RCX: 00007f2ffb321594
> [ 6401.629372] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
> [ 6401.629879] RBP: 00007ffe8d8eef40 R08: 0000000000000000 R09: 0000000000000000
> [ 6401.630384] R10: 55c926e3167eae79 R11: 0000000000000202 R12: 0000000000000003
> [ 6401.630889] R13: 00007ffe8d8ef030 R14: 0000000000000000 R15: 00007f2ffba4e668
> [ 6401.631394]  </TASK>
> [ 6401.631691] Modules linked in: tls nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 rfkill ip_set nf_tables nfnetlink qrtr sunrpc pktcdvd intel_rapl_msr snd_hda_codec_generic intel_rapl_common ledtrig_audio snd_hda_intel snd_intel_dspcfg snd_intel_sdw_acpi snd_hda_codec snd_hda_core snd_hwdep snd_pcm kvm_amd iTCO_wdt snd_timer intel_pmc_bxt ccp joydev iTCO_vendor_support kvm irqbypass i2c_i801 snd i2c_smbus soundcore lpc_ich virtio_balloon loop zram crct10dif_pclmul crc32_pclmul crc32c_intel polyval_clmulni polyval_generic ghash_clmulni_intel sha512_ssse3 sha256_ssse3 sha1_ssse3 virtio_net virtio_gpu virtio_console virtio_blk net_failover failover virtio_dma_buf serio_raw scsi_dh_rdac scsi_dh_emc scsi_dh_alua fuse dm_multipath qemu_fw_cfg
> [ 6401.636126] CR2: 0000000000000010
> [ 6401.636482] ---[ end trace 0000000000000000 ]---
> [ 6401.636891] RIP: 0010:hrtimer_active+0xd/0x50
> [ 6401.637288] Code: 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 0f 1f 44 00 00 48 8b 57 30 <8b> 42 10 a8 01 74 09 f3 90 8b 42 10 a8 01 75 f7 80 7f 38 00 75 1d
> [ 6401.638507] RSP: 0018:ffffb031009b7e10 EFLAGS: 00010286
> [ 6401.638951] RAX: 000000000002db00 RBX: ffff9118f786db08 RCX: 0000000000000000
> [ 6401.639478] RDX: 0000000000000000 RSI: ffff9117a0e64400 RDI: ffff9118f786db08
> [ 6401.640005] RBP: ffff9118f786db80 R08: ffff9117a0ddd420 R09: ffff9117804d4f70
> [ 6401.640535] R10: 0000000000000000 R11: 0000000000000000 R12: ffff9118f786db08
> [ 6401.641067] R13: ffff91178fdd5e20 R14: ffff9117840978c0 R15: 0000000000000000
> [ 6401.641601] FS:  00007f2ffbab1740(0000) GS:ffff9118f7840000(0000) knlGS:0000000000000000
> [ 6401.642174] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 6401.642653] CR2: 0000000000000010 CR3: 00000001b402e000 CR4: 0000000000750ee0
> [ 6401.643193] PKRU: 55555554
> [ 6401.643548] note: python3[2673] exited with irqs disabled
> 

I usually include crash data like the above in the change log too. But
clean it up a little. At least strip the timestamps. (Note, I do that with
emacs, by cut and pasting the dump in a scratch buffer and then using
vertical cut with "Ctrl-X r-k").

-- Steve

Re: [PATCH] tracing/timerlat: Move hrtimer_init to timerlat_fd open()

[Greg KH]

On Thu, Feb 01, 2024 at 05:02:56PM +0100, Daniel Bristot de Oliveira wrote:
> On 2/1/24 16:44, Greg KH wrote:
> > On Thu, Feb 01, 2024 at 04:13:39PM +0100, Daniel Bristot de Oliveira wrote:
> >> Currently, the timerlat's hrtimer is initialized at the first read of
> >> timerlat_fd, and destroyed at close(). It works, but it causes an error
> >> if the user program open() and close() the file without reading.
> > 
> > What error exactly happens?  Userspace, or the kernel crashes?
> 
> sorry, kernel crash:
> 
> # echo NO_OSNOISE_WORKLOAD > /sys/kernel/debug/tracing/osnoise/options
> # echo timerlat > /sys/kernel/debug/tracing/current_tracer
> 
> # cat ./timerlat_load.py
> #!/usr/bin/env python3
> 
> timerlat_fd = open("/sys/kernel/tracing/osnoise/per_cpu/cpu0/timerlat_fd", 'r')
> timerlat_fd.close();
> 
> # ./taskset -c 0 ./timerlat_load.py
> <BOOM>

Then obviously, this is a real, functional, change, so say so in the
kernel changelog :)

thanks,

greg k-h

Re: [PATCH] tracing/timerlat: Move hrtimer_init to timerlat_fd open()

[Steven Rostedt]

On Thu, 1 Feb 2024 10:05:59 -0800
Greg KH <gregkh@linuxfoundation.org> wrote:

> > timerlat_fd = open("/sys/kernel/tracing/osnoise/per_cpu/cpu0/timerlat_fd", 'r')
> > timerlat_fd.close();
> > 
> > # ./taskset -c 0 ./timerlat_load.py
> > <BOOM>  
> 
> Then obviously, this is a real, functional, change, so say so in the
> kernel changelog :)

I've updated the change log to remove that comment and add the reproducer.

-- Steve

Re: [PATCH] tracing/timerlat: Move hrtimer_init to timerlat_fd open()

[Greg KH]

On Thu, Feb 01, 2024 at 01:08:23PM -0500, Steven Rostedt wrote:
> On Thu, 1 Feb 2024 10:05:59 -0800
> Greg KH <gregkh@linuxfoundation.org> wrote:
> 
> > > timerlat_fd = open("/sys/kernel/tracing/osnoise/per_cpu/cpu0/timerlat_fd", 'r')
> > > timerlat_fd.close();
> > > 
> > > # ./taskset -c 0 ./timerlat_load.py
> > > <BOOM>  
> > 
> > Then obviously, this is a real, functional, change, so say so in the
> > kernel changelog :)
> 
> I've updated the change log to remove that comment and add the reproducer.

And cc: stable properly?  thanks!

Re: [PATCH] tracing/timerlat: Move hrtimer_init to timerlat_fd open()

[Steven Rostedt]

On Thu, 1 Feb 2024 10:12:50 -0800
Greg KH <gregkh@linuxfoundation.org> wrote:

> And cc: stable properly?  thanks!

The script I use automatically did that ;-)

-- Steve