]> Git Repo - linux.git/commit
sched_ext: Fix SCX_TASK_INIT -> SCX_TASK_READY transitions in scx_ops_enable()
authorTejun Heo <[email protected]>
Fri, 27 Sep 2024 20:02:40 +0000 (10:02 -1000)
committerTejun Heo <[email protected]>
Fri, 27 Sep 2024 20:02:40 +0000 (10:02 -1000)
commit9753358a6a2b011478e8efdabbb489216252426f
treed61ff3a4fabfce6779c91f3b5541829c00fdcf4d
parent8c2090c504e998c8f34ec870bae71dafcc96a6e0
sched_ext: Fix SCX_TASK_INIT -> SCX_TASK_READY transitions in scx_ops_enable()

scx_ops_enable() has two task iteration loops. The first one calls
scx_ops_init_task() on every task and the latter switches the eligible ones
into SCX. The first loop left the tasks in SCX_TASK_INIT state and then the
second loop switched it into READY before switching the task into SCX.

The distinction between INIT and READY is only meaningful in the fork path
where it's used to tell whether the task finished forking so that we can
tell ops.exit_task() accordingly. Leaving task in INIT state between the two
loops is incosistent with the fork path and incorrect. The following can be
triggered by running a program which keeps toggling a task between
SCHED_OTHER and SCHED_SCX while enabling a task:

  sched_ext: Invalid task state transition 1 -> 3 for fish[1526]
  WARNING: CPU: 2 PID: 1615 at kernel/sched/ext.c:3393 scx_ops_enable_task+0x1a1/0x200
  ...
  Sched_ext: qmap (enabling+all)
  RIP: 0010:scx_ops_enable_task+0x1a1/0x200
  ...
   switching_to_scx+0x13/0xa0
   __sched_setscheduler+0x850/0xa50
   do_sched_setscheduler+0x104/0x1c0
   __x64_sys_sched_setscheduler+0x18/0x30
   do_syscall_64+0x7b/0x140
   entry_SYSCALL_64_after_hwframe+0x76/0x7e

Fix it by transitioning to READY in the first loop right after
scx_ops_init_task() succeeds.

Signed-off-by: Tejun Heo <[email protected]>
Cc: David Vernet <[email protected]>
kernel/sched/ext.c
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