* printk: queue wake_up_klogd irq_work only if per-CPU areas are ready @ 2020-04-14 12:06 Sergey Senozhatsky 2020-04-14 12:14 ` Greg KH 0 siblings, 1 reply; 4+ messages in thread From: Sergey Senozhatsky @ 2020-04-14 12:06 UTC (permalink / raw) To: stable; +Cc: Petr Mladek Hello, Commit ab6f762f0f53162d41 Linus' HEAD. printk_deferred() does not make sure that it's safe to write to per-CPU data, which causes problems when printk_deferred() is invoked "too early", before per-CPU areas are initialized. There are multiple bug reports, e.g. https://bugzilla.kernel.org/show_bug.cgi?id=206847 -ss ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: printk: queue wake_up_klogd irq_work only if per-CPU areas are ready 2020-04-14 12:06 printk: queue wake_up_klogd irq_work only if per-CPU areas are ready Sergey Senozhatsky @ 2020-04-14 12:14 ` Greg KH 2020-04-14 13:13 ` Sergey Senozhatsky 0 siblings, 1 reply; 4+ messages in thread From: Greg KH @ 2020-04-14 12:14 UTC (permalink / raw) To: Sergey Senozhatsky; +Cc: stable, Petr Mladek On Tue, Apr 14, 2020 at 09:06:13PM +0900, Sergey Senozhatsky wrote: > Hello, > > Commit ab6f762f0f53162d41 Linus' HEAD. > > printk_deferred() does not make sure that it's safe to write to > per-CPU data, which causes problems when printk_deferred() is > invoked "too early", before per-CPU areas are initialized. There > are multiple bug reports, e.g. > https://bugzilla.kernel.org/show_bug.cgi?id=206847 > > -ss So where do you want this commit backported to? thanks, greg k-h ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: printk: queue wake_up_klogd irq_work only if per-CPU areas are ready 2020-04-14 12:14 ` Greg KH @ 2020-04-14 13:13 ` Sergey Senozhatsky 2020-07-20 12:50 ` Greg KH 0 siblings, 1 reply; 4+ messages in thread From: Sergey Senozhatsky @ 2020-04-14 13:13 UTC (permalink / raw) To: Greg KH; +Cc: Sergey Senozhatsky, stable, Petr Mladek On (20/04/14 14:14), Greg KH wrote: > On Tue, Apr 14, 2020 at 09:06:13PM +0900, Sergey Senozhatsky wrote: > > Hello, > > > > Commit ab6f762f0f53162d41 Linus' HEAD. > > > > printk_deferred() does not make sure that it's safe to write to > > per-CPU data, which causes problems when printk_deferred() is > > invoked "too early", before per-CPU areas are initialized. There > > are multiple bug reports, e.g. > > https://bugzilla.kernel.org/show_bug.cgi?id=206847 > > > > -ss > > So where do you want this commit backported to? Well, printk() is affected in all the kernels where printk_deferred() relies on per-CPU data. Which may translate to "pretty much all current stable kernels?" This patch, however, uses printk_safe() bits, so it won't apply on pre-printk_safe() kernels (not sure if we have such -stable kernels though). -ss ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: printk: queue wake_up_klogd irq_work only if per-CPU areas are ready 2020-04-14 13:13 ` Sergey Senozhatsky @ 2020-07-20 12:50 ` Greg KH 0 siblings, 0 replies; 4+ messages in thread From: Greg KH @ 2020-07-20 12:50 UTC (permalink / raw) To: Sergey Senozhatsky; +Cc: stable, Petr Mladek On Tue, Apr 14, 2020 at 10:13:09PM +0900, Sergey Senozhatsky wrote: > On (20/04/14 14:14), Greg KH wrote: > > On Tue, Apr 14, 2020 at 09:06:13PM +0900, Sergey Senozhatsky wrote: > > > Hello, > > > > > > Commit ab6f762f0f53162d41 Linus' HEAD. > > > > > > printk_deferred() does not make sure that it's safe to write to > > > per-CPU data, which causes problems when printk_deferred() is > > > invoked "too early", before per-CPU areas are initialized. There > > > are multiple bug reports, e.g. > > > https://bugzilla.kernel.org/show_bug.cgi?id=206847 > > > > > > -ss > > > > So where do you want this commit backported to? > > Well, printk() is affected in all the kernels where > printk_deferred() relies on per-CPU data. Which may > translate to "pretty much all current stable kernels?" > This patch, however, uses printk_safe() bits, so it > won't apply on pre-printk_safe() kernels (not sure if > we have such -stable kernels though). This is already in the 5.4.y tree, so I've added it to 4.19.y, but I could not apply it to anything older (4.14.y, 4.9.y, 4.4.y) as it did not apply there. If you want it in those older kernels, and you think it is really needed, please feel free to send a backported version for them. thanks, greg k-h ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2020-07-20 12:50 UTC | newest] Thread overview: 4+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2020-04-14 12:06 printk: queue wake_up_klogd irq_work only if per-CPU areas are ready Sergey Senozhatsky 2020-04-14 12:14 ` Greg KH 2020-04-14 13:13 ` Sergey Senozhatsky 2020-07-20 12:50 ` Greg KH
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