d/freebsd-skq
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Reduce chance of RCU deadlock in the LinuxKPI by implementing the section

Browse Source 
feature of the concurrency kit, CK.

Differential Revision:	https://reviews.freebsd.org/D29467
Reviewed by:	kib@ and markj@
MFC after:	1 week
Sponsored by:	Mellanox Technologies // NVIDIA Networking
This commit is contained in:
Hans Petter Selasky 2021-03-28 09:36:48 +02:00
parent 19318a62d7
commit 1777720880
2 changed files with 33 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
sys/compat/linuxkpi/common/include/linux/sched.h
View File

@ -82,6 +82,7 @@ struct task_struct {
int bsd_interrupt_value;
struct work_struct *work; /* current work struct, if set */
struct task_struct *group_leader;
unsigned rcu_section[TS_RCU_TYPE_MAX];
};
#define current ({ \

39
sys/compat/linuxkpi/common/src/linux_rcu.c
View File

@ -1,6 +1,6 @@
/*-
* Copyright (c) 2016 Matthew Macy (mmacy@mattmacy.io)
* Copyright (c) 2017-2020 Hans Petter Selasky (hselasky@freebsd.org)
* Copyright (c) 2017-2021 Hans Petter Selasky (hselasky@freebsd.org)
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@ -85,6 +85,15 @@ struct linux_epoch_record {
*/
CTASSERT(sizeof(struct rcu_head) == sizeof(struct callback_head));
/*
* Verify that "rcu_section[0]" has the same size as
* "ck_epoch_section_t". This has been done to avoid having to add
* special compile flags for including ck_epoch.h to all clients of
* the LinuxKPI.
*/
CTASSERT(sizeof(((struct task_struct *)0)->rcu_section[0] ==
sizeof(ck_epoch_section_t)));
/*
* Verify that "epoch_record" is at beginning of "struct
* linux_epoch_record":
@ -189,6 +198,14 @@ linux_rcu_read_lock(unsigned type)
if (RCU_SKIP())
return;
ts = current;
/* assert valid refcount */
MPASS(ts->rcu_recurse[type] != INT_MAX);
if (++(ts->rcu_recurse[type]) != 1)
return;
/*
* Pin thread to current CPU so that the unlock code gets the
* same per-CPU epoch record:
@ -196,16 +213,14 @@ linux_rcu_read_lock(unsigned type)
sched_pin();
record = &DPCPU_GET(linux_epoch_record[type]);
ts = current;
/*
* Use a critical section to prevent recursion inside
* ck_epoch_begin(). Else this function supports recursion.
*/
critical_enter();
ck_epoch_begin(&record->epoch_record, NULL);
ts->rcu_recurse[type]++;
if (ts->rcu_recurse[type] == 1)
ck_epoch_begin(&record->epoch_record,
(ck_epoch_section_t *)&ts->rcu_section[type]);
TAILQ_INSERT_TAIL(&record->ts_head, ts, rcu_entry[type]);
critical_exit();
}
@ -221,17 +236,23 @@ linux_rcu_read_unlock(unsigned type)
if (RCU_SKIP())
return;
record = &DPCPU_GET(linux_epoch_record[type]);
ts = current;
/* assert valid refcount */
MPASS(ts->rcu_recurse[type] > 0);
if (--(ts->rcu_recurse[type]) != 0)
return;
record = &DPCPU_GET(linux_epoch_record[type]);
/*
* Use a critical section to prevent recursion inside
* ck_epoch_end(). Else this function supports recursion.
*/
critical_enter();
ck_epoch_end(&record->epoch_record, NULL);
ts->rcu_recurse[type]--;
if (ts->rcu_recurse[type] == 0)
ck_epoch_end(&record->epoch_record,
(ck_epoch_section_t *)&ts->rcu_section[type]);
TAILQ_REMOVE(&record->ts_head, ts, rcu_entry[type]);
critical_exit();