Messages in this thread |  | | Date | Wed, 28 Mar 2018 14:47:54 +0800 | From | Boqun Feng <> | Subject | Re: [RFC PATCH for 4.17 02/21] rseq: Introduce restartable sequences system call (v12) |
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On Tue, Mar 27, 2018 at 12:05:23PM -0400, Mathieu Desnoyers wrote: [...] > Changes since v11: > > - Replace task struct rseq_preempt, rseq_signal, and rseq_migrate > bool by u32 rseq_event_mask. [...] > @@ -979,6 +980,17 @@ struct task_struct { > unsigned long numa_pages_migrated; > #endif /* CONFIG_NUMA_BALANCING */ > > +#ifdef CONFIG_RSEQ > + struct rseq __user *rseq; > + u32 rseq_len; > + u32 rseq_sig; > + /* > + * RmW on rseq_event_mask must be performed atomically > + * with respect to preemption. > + */ > + unsigned long rseq_event_mask;
s/unsigned long/u32
> +#endif > + > struct tlbflush_unmap_batch tlb_ubc; > > struct rcu_head rcu; > @@ -1688,4 +1700,110 @@ extern long sched_getaffinity(pid_t pid, struct cpumask *mask); > #define TASK_SIZE_OF(tsk) TASK_SIZE > #endif >
[...]
> + > +static int rseq_ip_fixup(struct pt_regs *regs) > +{ > + unsigned long ip = instruction_pointer(regs), start_ip = 0, > + post_commit_offset = 0, abort_ip = 0; > + struct task_struct *t = current; > + uint32_t cs_flags = 0; > + bool in_rseq_cs = false;
This seems unnecessary? Because..
> + int ret; > + > + ret = rseq_get_rseq_cs(t, &start_ip, &post_commit_offset, &abort_ip, > + &cs_flags); > + if (ret) > + return ret; > + > + /* > + * Handle potentially not being within a critical section. > + * Unsigned comparison will be true when > + * ip >= start_ip, and when ip < start_ip + post_commit_offset. > + */ > + if (ip - start_ip < post_commit_offset) > + in_rseq_cs = true; > + > + /* > + * If not nested over a rseq critical section, restart is > + * useless. Clear the rseq_cs pointer and return. > + */ > + if (!in_rseq_cs) > + return clear_rseq_cs(t);
we can write
if (ip - start_ip >= post_commit_offset) return clear_rseq_cs(t);
Regards, Boqun
> + ret = rseq_need_restart(t, cs_flags); > + if (ret <= 0) > + return ret; > + ret = clear_rseq_cs(t); > + if (ret) > + return ret; > + trace_rseq_ip_fixup(ip, start_ip, post_commit_offset, abort_ip); > + instruction_pointer_set(regs, (unsigned long)abort_ip); > + return 0; > +} > + [...] [unhandled content-type:application/pgp-signature] |  |