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using dev_coredumpv

DISCUSSION Arend van Spriel 2 participants 3 messages Sep 7, 2015

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Arend van Spriel

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Hi Johannes,

I am looking at devcoredump subsystem and I was wondering about the lifetime of the devcd folder. With dev_coredumpm() the description says: "If a previous one hasn't been read yet, the new coredump is discarded.". I am wondering what "read" means here. For testing I call dev_coredumpv() every second, but when I hexdump the data file it does not create a new devcd folder. That only occurs after 5 minutes. Is that expected?

Regards,
Arend

#1 lore raw
Quoted 9 lines · Arend van Spriel

Hi Johannes,

I am looking at devcoredump subsystem and I was wondering about the lifetime of the devcd folder. With dev_coredumpm() the description says:
"If a previous one hasn't been read yet, the new coredump is discarded.". I am wondering what "read" means here. For testing I call dev_coredumpv() every second, but when I hexdump the data file it does not create a new devcd folder. That only occurs after 5 minutes. Is that expected?

I suppose "read" should say "discarded by userspace", but I always assumed userspace would read the file and then discard the coredump by writing (anything iirc) to the file.

IOW - yes, this is expected, you should write to the data file which makes it (and the folder) disappear and allows creating a new one.

johannes

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#2 lore raw
Quoted 11 lines · Johannes Berg
Quoted 9 lines · Arend van Spriel

Hi Johannes,

I am looking at devcoredump subsystem and I was wondering about the lifetime of the devcd folder. With dev_coredumpm() the description says:
"If a previous one hasn't been read yet, the new coredump is discarded.". I am wondering what "read" means here. For testing I call dev_coredumpv() every second, but when I hexdump the data file it does not create a new devcd folder. That only occurs after 5 minutes. Is that expected?

Quoted 3 lines

I suppose "read" should say "discarded by userspace", but I always assumed userspace would read the file and then discard the coredump by writing (anything iirc) to the file.

Thanks. Went back to devcoredump.c and reading the code found that devcd_data_write schedules devcd_del work without any condition. Sorry for being lazy.

Gr. AvS

Quoted 5 lines

IOW - yes, this is expected, you should write to the data file which makes it (and the folder) disappear and allows creating a new one.

johannes