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Fix a LOR between pmc_sx and proctree/allproc when creating a new thread

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for the pmclog.

Reported by:	Ryan Stone <rstone at sandvine dot com>
Tested by:	Ryan Stone <rstone at sandvine dot com>
Sponsored by:	Sandvine Incorporated
This commit is contained in:
Attilio Rao 2009-06-25 20:59:37 +00:00
parent c3380d406a
commit ca2d94bef7
2 changed files with 19 additions and 7 deletions
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7
sys/dev/hwpmc/hwpmc_logging.c
View File

@ -44,6 +44,7 @@ __FBSDID("$FreeBSD$");
#include <sys/module.h>
#include <sys/mutex.h>
#include <sys/pmc.h>
#include <sys/pmckern.h>
#include <sys/pmclog.h>
#include <sys/proc.h>
#include <sys/signalvar.h>
@ -552,6 +553,12 @@ pmclog_configure_log(struct pmc_mdep *md, struct pmc_owner *po, int logfd)
int error;
struct proc *p;
/*
* As long as it is possible to get a LOR between pmc_sx lock and
* proctree/allproc sx locks used for adding a new process, assure
* the former is not held here.
*/
sx_assert(&pmc_sx, SA_UNLOCKED);
PMCDBG(LOG,CFG,1, "config po=%p logfd=%d", po, logfd);
p = po->po_owner;

19
sys/dev/hwpmc/hwpmc_mod.c
View File

@ -2663,7 +2663,7 @@ static const char *pmc_op_to_name[] = {
static int
pmc_syscall_handler(struct thread *td, void *syscall_args)
{
int error, is_sx_downgraded, op;
int error, is_sx_downgraded, is_sx_locked, op;
struct pmc_syscall_args *c;
void *arg;
@ -2672,6 +2672,7 @@ pmc_syscall_handler(struct thread *td, void *syscall_args)
DROP_GIANT();
is_sx_downgraded = 0;
is_sx_locked = 1;
c = (struct pmc_syscall_args *) syscall_args;
@ -2720,9 +2721,11 @@ pmc_syscall_handler(struct thread *td, void *syscall_args)
* a log file configured, flush its buffers and
* de-configure it.
*/
if (cl.pm_logfd >= 0)
if (cl.pm_logfd >= 0) {
sx_xunlock(&pmc_sx);
is_sx_locked = 0;
error = pmclog_configure_log(md, po, cl.pm_logfd);
else if (po->po_flags & PMC_PO_OWNS_LOGFILE) {
} else if (po->po_flags & PMC_PO_OWNS_LOGFILE) {
pmclog_process_closelog(po);
error = pmclog_flush(po);
if (error == 0) {
@ -3772,10 +3775,12 @@ pmc_syscall_handler(struct thread *td, void *syscall_args)
break;
}
if (is_sx_downgraded)
sx_sunlock(&pmc_sx);
else
sx_xunlock(&pmc_sx);
if (is_sx_locked != 0) {
if (is_sx_downgraded)
sx_sunlock(&pmc_sx);
else
sx_xunlock(&pmc_sx);
}
if (error)
atomic_add_int(&pmc_stats.pm_syscall_errors, 1);