Messages in this thread | | | Subject | Re: [PATCH] fs: proc: use down_read_killable in proc_pid_cmdline_read() | From | Yang Shi <> | Date | Fri, 23 Feb 2018 11:42:34 -0800 |
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On 2/23/18 11:33 AM, Alexey Dobriyan wrote: > On Wed, Feb 21, 2018 at 03:13:10PM -0800, Yang Shi wrote: > >>>>> 2) access_remote_vm() et al will do the same ->mmap_sem, and >>>> Yes, it does. But, __access_remote_vm() is called by access_process_vm() >>>> too, which is used by much more places, i.e. ptrace, so I was not sure >>>> if it is preferred to convert to killable version. So, I leave it untouched. >>> Yeah, but ->mmap_sem is taken 3 times per /proc/*/cmdline read >>> and your scalability tests should trigger next backtrace right away. >> Yes, however, I didn't run into it if mmap_sem is acquired earlier. >> >> How about defining a killable version, like >> __access_remote_vm_killable() which use down_read_killable(), then the >> killable version can be used by proc/*/cmdline? There might be other >> users in the future. > It would be a disaster as interfaces multiply.
Might be not that bad. Just need add:
__access_remote_vm_killable() access_remote_vm_killable()
Then access_process_vm() keep using __access_remote_vm(). And, use access_remote_vm_killable() in fs/proc/base. And, it looks the access_process_vm() calls in get_cmdline() can be changed to access_remote_vm() (non killable version).
Yang
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