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epoch(9): make recursion lighter weight

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There isn't any real work to do except bump td_epochnest when recursing.
Skip the additional work in this case.

Approved by:	sbruno
This commit is contained in:
Matt Macy 2018-05-17 01:13:40 +00:00
parent 93c0bfb85b
commit fdf71aeb54
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=333697
2 changed files with 38 additions and 24 deletions
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31
sys/kern/subr_epoch.c
View File

@ -284,21 +284,15 @@ epoch_free(epoch_t epoch)
} while (0)
void
epoch_enter(epoch_t epoch)
epoch_enter_internal(epoch_t epoch, struct thread *td)
{
struct epoch_pcpu_state *eps;
struct thread *td;
INIT_CHECK(epoch);
td = curthread;
critical_enter();
eps = epoch->e_pcpu[curcpu];
td->td_epochnest++;
MPASS(td->td_epochnest < UCHAR_MAX - 2);
if (td->td_epochnest == 1)
TAILQ_INSERT_TAIL(&eps->eps_record.er_tdlist, td, td_epochq);
#ifdef INVARIANTS
MPASS(td->td_epochnest < UCHAR_MAX - 2);
if (td->td_epochnest > 1) {
struct thread *curtd;
int found = 0;
@ -307,38 +301,31 @@ epoch_enter(epoch_t epoch)
if (curtd == td)
found = 1;
KASSERT(found, ("recursing on a second epoch"));
}
#endif
if (td->td_epochnest > 1) {
critical_exit();
return;
}
#endif
TAILQ_INSERT_TAIL(&eps->eps_record.er_tdlist, td, td_epochq);
sched_pin();
ck_epoch_begin(&eps->eps_record.er_record, (ck_epoch_section_t*)&td->td_epoch_section);
critical_exit();
}
void
epoch_exit(epoch_t epoch)
epoch_exit_internal(epoch_t epoch, struct thread *td)
{
struct epoch_pcpu_state *eps;
struct thread *td;
td = curthread;
MPASS(td->td_epochnest == 0);
INIT_CHECK(epoch);
MPASS(td->td_epochnest);
critical_enter();
eps = epoch->e_pcpu[curcpu];
td->td_epochnest--;
if (td->td_epochnest == 0)
TAILQ_REMOVE(&eps->eps_record.er_tdlist, td, td_epochq);
else {
critical_exit();
return;
}
sched_unpin();
ck_epoch_end(&eps->eps_record.er_record, (ck_epoch_section_t*)&td->td_epoch_section);
TAILQ_REMOVE(&eps->eps_record.er_tdlist, td, td_epochq);
eps->eps_record.er_gen++;
sched_unpin();
critical_exit();
}

31
sys/sys/epoch.h
View File

@ -29,6 +29,8 @@
#ifndef _SYS_EPOCH_H_
#define _SYS_EPOCH_H_
#include <sys/lock.h>
#include <sys/proc.h>
struct epoch;
typedef struct epoch *epoch_t;
@ -43,10 +45,35 @@ typedef struct epoch_context *epoch_context_t;
epoch_t epoch_alloc(void);
void epoch_free(epoch_t epoch);
void epoch_enter(epoch_t epoch);
void epoch_exit(epoch_t epoch);
void epoch_enter_internal(epoch_t epoch, struct thread *td);
void epoch_exit_internal(epoch_t epoch, struct thread *td);
void epoch_wait(epoch_t epoch);
void epoch_call(epoch_t epoch, epoch_context_t ctx, void (*callback) (epoch_context_t));
int in_epoch(void);
static __inline void
epoch_enter(epoch_t epoch)
{
struct thread *td;
int nesting;
td = curthread;
nesting = td->td_epochnest++;
#ifndef INVARIANTS
if (nesting == 0)
#endif
epoch_enter_internal(epoch, td);
}
static __inline void
epoch_exit(epoch_t epoch)
{
struct thread *td;
td = curthread;
MPASS(td->td_epochnest);
if (td->td_epochnest-- == 1)
epoch_exit_internal(epoch, td);
}
#endif