9cc6fea175
- Add a comment to explain that the preempt_disable() before unlocking
tasklist lock is not a correctness problem and just avoids the tracer
to preempt the tracee before the tracee schedules out.
- Make that preempt_disable() conditional on PREEMPT_RT=n.
RT enabled kernels cannot disable preemption at this point because
cgroup_enter_frozen() and sched_submit_work() acquire spinlocks or
rwlocks which are substituted by sleeping locks on RT. Acquiring a
sleeping lock in a preemption disable region is obviously not possible.
This obviously brings back the potential slowdown of ptrace() for RT
enabled kernels, but that's a price to be payed for latency guarantees.
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Merge tag 'core-core-2023-10-29-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull core updates from Thomas Gleixner:
"Two small updates to ptrace_stop():
- Add a comment to explain that the preempt_disable() before
unlocking tasklist lock is not a correctness problem and just
avoids the tracer to preempt the tracee before the tracee schedules
out.
- Make that preempt_disable() conditional on PREEMPT_RT=n.
RT enabled kernels cannot disable preemption at this point because
cgroup_enter_frozen() and sched_submit_work() acquire spinlocks or
rwlocks which are substituted by sleeping locks on RT. Acquiring a
sleeping lock in a preemption disable region is obviously not
possible.
This obviously brings back the potential slowdown of ptrace() for
RT enabled kernels, but that's a price to be paid for latency
guarantees"
* tag 'core-core-2023-10-29-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
signal: Don't disable preemption in ptrace_stop() on PREEMPT_RT
signal: Add a proper comment about preempt_disable() in ptrace_stop()
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.