Re: [PATCH 6/6] sched: Change task_struct::state
From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: 2021-06-02 14:09:07
Also in:
cgroups, dm-devel, kvm, linux-block, linux-fsdevel, linux-mm, linux-pm, linux-usb, lkml, netdev, rcu
----- On Jun 2, 2021, at 9:12 AM, Peter Zijlstra peterz@infradead.org wrote:
Change the type and name of task_struct::state. Drop the volatile and shrink it to an 'unsigned int'. Rename it in order to find all uses such that we can use READ_ONCE/WRITE_ONCE as appropriate.
[...]
quoted hunk ↗ jump to hunk
--- a/block/blk-mq.c +++ b/block/blk-mq.c
[...]
quoted hunk ↗ jump to hunk
@@ -1559,7 +1560,8 @@ static int fill_psinfo(struct elf_prpsinpsinfo->pr_pgrp = task_pgrp_vnr(p); psinfo->pr_sid = task_session_vnr(p); - i = p->state ? ffz(~p->state) + 1 : 0; + state = READ_ONCE(p->__state); + i = state ? ffz(~state) + 1 : 0; psinfo->pr_state = i; psinfo->pr_sname = (i > 5) ? '.' : "RSDTZW"[i]; psinfo->pr_zomb = psinfo->pr_sname == 'Z';
[...]
quoted hunk ↗ jump to hunk
--- a/include/linux/sched.h +++ b/include/linux/sched.h@@ -113,13 +113,13 @@ struct task_group;__TASK_TRACED | EXIT_DEAD | EXIT_ZOMBIE | \ TASK_PARKED) -#define task_is_running(task) (READ_ONCE((task)->state) == TASK_RUNNING) +#define task_is_running(task) (READ_ONCE((task)->__state) == TASK_RUNNING) -#define task_is_traced(task) ((task->state & __TASK_TRACED) != 0) +#define task_is_traced(task) ((READ_ONCE(task->__state) & __TASK_TRACED) != 0) -#define task_is_stopped(task) ((task->state & __TASK_STOPPED) != 0) +#define task_is_stopped(task) ((READ_ONCE(task->__state) & __TASK_STOPPED) != 0) -#define task_is_stopped_or_traced(task) ((task->state & (__TASK_STOPPED | __TASK_TRACED)) != 0) +#define task_is_stopped_or_traced(task) ((READ_ONCE(task->__state) & (__TASK_STOPPED | __TASK_TRACED)) != 0) #ifdef CONFIG_DEBUG_ATOMIC_SLEEP@@ -134,14 +134,14 @@ struct task_group;do { \ WARN_ON_ONCE(is_special_task_state(state_value));\ current->task_state_change = _THIS_IP_; \ - current->state = (state_value); \ + WRITE_ONCE(current->__state, (state_value)); \ } while (0)
Why not introduce set_task_state(p) and get_task_state(p) rather than sprinkle READ_ONCE() and WRITE_ONCE() all over the kernel ? Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com