* arm64: pstore: printk causing hang during boot in __memcpy_toio with pstore enabled
@ 2018-08-01 12:35 Ivid Suvarna
2018-08-01 13:19 ` Guenter Roeck
0 siblings, 1 reply; 5+ messages in thread
From: Ivid Suvarna @ 2018-08-01 12:35 UTC (permalink / raw)
To: Kees Cook, Arnd Bergmann, Guenter Roeck, Greg Kroah-Hartman,
Linus Torvalds, Jason Baron
Cc: Kernel development list, Joe Perches, linux-arm-msm
Hi,
When pstore is enabled and a *pr_info(any printk) in
__memcpy_toio(arch/arm64/kernel/io.c)* is added, kernel wont boot and
just hangs.
The path where __memcpy_toio is called is below:
->persistent_ram_update
-> memcpy_toio
-> __memcpy_toio
I tried with trace_printk and kernel boots fine. I understand that
printk has overhead, but is this expected when we use some printk
statement in __memcpy_toio?
Or is it some kind of bug? Tested on db410c.
Please let me know your opinion.
Thanks,
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: arm64: pstore: printk causing hang during boot in __memcpy_toio with pstore enabled 2018-08-01 12:35 arm64: pstore: printk causing hang during boot in __memcpy_toio with pstore enabled Ivid Suvarna @ 2018-08-01 13:19 ` Guenter Roeck 2018-08-01 17:16 ` Ivid Suvarna 0 siblings, 1 reply; 5+ messages in thread From: Guenter Roeck @ 2018-08-01 13:19 UTC (permalink / raw) To: Ivid Suvarna, Kees Cook, Arnd Bergmann, Greg Kroah-Hartman, Linus Torvalds, Jason Baron Cc: Kernel development list, Joe Perches, linux-arm-msm On 08/01/2018 05:35 AM, Ivid Suvarna wrote: > Hi, > > When pstore is enabled and a *pr_info(any printk) in > __memcpy_toio(arch/arm64/kernel/io.c)* is added, kernel wont boot and > just hangs. > > The path where __memcpy_toio is called is below: > > ->persistent_ram_update > -> memcpy_toio > -> __memcpy_toio > > I tried with trace_printk and kernel boots fine. I understand that > printk has overhead, but is this expected when we use some printk > statement in __memcpy_toio? > I think the problem may be that the printk() output is copied to pstore. Since pstore calls memcpy_toio(), you get a nice recursion if you add a printk() call to it. Guenter ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: arm64: pstore: printk causing hang during boot in __memcpy_toio with pstore enabled 2018-08-01 13:19 ` Guenter Roeck @ 2018-08-01 17:16 ` Ivid Suvarna 2018-08-01 17:25 ` Guenter Roeck 0 siblings, 1 reply; 5+ messages in thread From: Ivid Suvarna @ 2018-08-01 17:16 UTC (permalink / raw) To: Guenter Roeck Cc: Kees Cook, Arnd Bergmann, Greg Kroah-Hartman, Linus Torvalds, Jason Baron, Kernel development list, Joe Perches, linux-arm-msm On Wed, Aug 1, 2018 at 6:49 PM, Guenter Roeck <linux@roeck-us.net> wrote: > On 08/01/2018 05:35 AM, Ivid Suvarna wrote: >> >> Hi, >> >> When pstore is enabled and a *pr_info(any printk) in >> __memcpy_toio(arch/arm64/kernel/io.c)* is added, kernel wont boot and >> just hangs. >> >> The path where __memcpy_toio is called is below: >> >> ->persistent_ram_update >> -> memcpy_toio >> -> __memcpy_toio >> >> I tried with trace_printk and kernel boots fine. I understand that >> printk has overhead, but is this expected when we use some printk >> statement in __memcpy_toio? >> > > I think the problem may be that the printk() output is copied to pstore. > Since pstore calls memcpy_toio(), you get a nice recursion if you add a > printk() call to it. > Is there any solution to this other than not adding printk :p ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: arm64: pstore: printk causing hang during boot in __memcpy_toio with pstore enabled 2018-08-01 17:16 ` Ivid Suvarna @ 2018-08-01 17:25 ` Guenter Roeck 2018-08-01 17:51 ` Ivid Suvarna 0 siblings, 1 reply; 5+ messages in thread From: Guenter Roeck @ 2018-08-01 17:25 UTC (permalink / raw) To: Ivid Suvarna Cc: Kees Cook, Arnd Bergmann, Greg Kroah-Hartman, Linus Torvalds, Jason Baron, Kernel development list, Joe Perches, linux-arm-msm On Wed, Aug 01, 2018 at 10:46:06PM +0530, Ivid Suvarna wrote: > On Wed, Aug 1, 2018 at 6:49 PM, Guenter Roeck <linux@roeck-us.net> wrote: > > On 08/01/2018 05:35 AM, Ivid Suvarna wrote: > >> > >> Hi, > >> > >> When pstore is enabled and a *pr_info(any printk) in > >> __memcpy_toio(arch/arm64/kernel/io.c)* is added, kernel wont boot and > >> just hangs. > >> > >> The path where __memcpy_toio is called is below: > >> > >> ->persistent_ram_update > >> -> memcpy_toio > >> -> __memcpy_toio > >> > >> I tried with trace_printk and kernel boots fine. I understand that > >> printk has overhead, but is this expected when we use some printk > >> statement in __memcpy_toio? > >> > > > > I think the problem may be that the printk() output is copied to pstore. > > Since pstore calls memcpy_toio(), you get a nice recursion if you add a > > printk() call to it. > > > > Is there any solution to this other than not adding printk :p Well, disabling pstore would help. You could also use a trace function, as you already found out, or you could use gdb for debugging. Since this is obviously a debug image, you should be willing to accept some limitations/restrictions. Guenter ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: arm64: pstore: printk causing hang during boot in __memcpy_toio with pstore enabled 2018-08-01 17:25 ` Guenter Roeck @ 2018-08-01 17:51 ` Ivid Suvarna 0 siblings, 0 replies; 5+ messages in thread From: Ivid Suvarna @ 2018-08-01 17:51 UTC (permalink / raw) To: Guenter Roeck Cc: Kees Cook, Arnd Bergmann, Greg Kroah-Hartman, Linus Torvalds, Jason Baron, Kernel development list, Joe Perches, linux-arm-msm On Wed, Aug 1, 2018 at 10:55 PM, Guenter Roeck <linux@roeck-us.net> wrote: > On Wed, Aug 01, 2018 at 10:46:06PM +0530, Ivid Suvarna wrote: >> On Wed, Aug 1, 2018 at 6:49 PM, Guenter Roeck <linux@roeck-us.net> wrote: >> > On 08/01/2018 05:35 AM, Ivid Suvarna wrote: >> >> >> >> Hi, >> >> >> >> When pstore is enabled and a *pr_info(any printk) in >> >> __memcpy_toio(arch/arm64/kernel/io.c)* is added, kernel wont boot and >> >> just hangs. >> >> >> >> The path where __memcpy_toio is called is below: >> >> >> >> ->persistent_ram_update >> >> -> memcpy_toio >> >> -> __memcpy_toio >> >> >> >> I tried with trace_printk and kernel boots fine. I understand that >> >> printk has overhead, but is this expected when we use some printk >> >> statement in __memcpy_toio? >> >> >> > >> > I think the problem may be that the printk() output is copied to pstore. >> > Since pstore calls memcpy_toio(), you get a nice recursion if you add a >> > printk() call to it. >> > >> >> Is there any solution to this other than not adding printk :p > > Well, disabling pstore would help. You could also use a trace function, > as you already found out, or you could use gdb for debugging. Since > this is obviously a debug image, you should be willing to accept some > limitations/restrictions. > Ok. But trace_printk output is available only after boot, so to debug any boot issues, it may not be helpful. And gdb for kernel debugging? Maybe u meant kgdb? Let me check if this issue is only for pstore path or not. ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2018-08-01 17:51 UTC | newest] Thread overview: 5+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2018-08-01 12:35 arm64: pstore: printk causing hang during boot in __memcpy_toio with pstore enabled Ivid Suvarna 2018-08-01 13:19 ` Guenter Roeck 2018-08-01 17:16 ` Ivid Suvarna 2018-08-01 17:25 ` Guenter Roeck 2018-08-01 17:51 ` Ivid Suvarna
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