Messages in this thread | | | Date | Sat, 28 Jul 2018 16:13:14 +0200 | From | Pavel Machek <> | Subject | Re: [RFC PATCH for 4.18 00/16] Restartable Sequences |
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Hi!
> Documentation-wise, I have posted a rseq man page rfc here: > > https://lkml.kernel.org/r/20180616195803.29877-1-mathieu.desnoyers@efficios.com > > comments are welcome!
Thanks for pointer.
+Restartable sequences are atomic with respect to preemption (making it +atomic with respect to other threads running on the same CPU), as well +as signal delivery (user-space execution contexts nested over the same +thread).
So the threads are protected against sigkill when running the restartable sequence?
+Restartable sequences must not perform system calls. Doing so may result +in termination of the process by a segmentation fault. +
"may result"? It would be nice to always catch that.
+Optimistic cache of the CPU number on which the current thread is +running. Its value is guaranteed to always be a possible CPU number, +even when rseq is not initialized. The value it contains should always +be confirmed by reading the cpu_id field.
I'm not sure what "optimistic cache" is...
+Flags indicating the restart behavior for the current thread. This is +mainly used for debugging purposes. Can be either: +.IP \[bu] +RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT +.IP \[bu] +RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL +.IP \[bu]
Flags tell me there may be more then one, but "can be either" tells me just one flag is allowed.
+.B Structure alignment +This structure is aligned on multiples of 32 bytes. +.TP +.B Structure size +This structure has a fixed size of 32 bytes. +.B Structure alignment +This structure is aligned on multiples of 32 bytes. +.TP +.B Structure size +This structure has a fixed size of 32 bytes.
I believe we normally say "is aligned on 32-bytes boundary". (Will not this need to be bigger on machines with bigger cache sizes?)
above it says:
+.B Structure size +This structure is extensible. Its size is passed as parameter to the +rseq system call.
I'm reading source, so maybe it refers to different structure.
Thanks, Pavel
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