Messages in this thread Patch in this message | | | Date | Thu, 16 Feb 2012 23:29:52 +0400 | From | Cyrill Gorcunov <> | Subject | Re: + syscalls-x86-add-__nr_kcmp-syscall-v8.patch added to -mm tree |
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On Thu, Feb 16, 2012 at 08:03:21PM +0100, Oleg Nesterov wrote: > On 02/16, Cyrill Gorcunov wrote: > > > > On Thu, Feb 16, 2012 at 06:40:47PM +0100, Oleg Nesterov wrote: > > > On 02/16, Cyrill Gorcunov wrote: > > > > > > > > -static void access_unlock(struct task_struct *task) > > > > +static void kcmp_unlock(struct mutex *m1, struct mutex *m2) > > > > { > > > > - mutex_unlock(&task->signal->cred_guard_mutex); > > > > + if (m2 > m1) > > > > + swap(m1, m2); > > > > > > Well, the order doesn't matter in case of _unlock, you can remove > > > this part. Not that it really hurts though, I won't argue. > > > > It drops some instructions so I think it worth removing > > Yes. >
Final one ;) I agreed on every line of your comment, thanks a lot Oleg! --- From: Cyrill Gorcunov <gorcunov@openvz.org> Subject: syscalls, x86: Make __NR_kcmp to work with equivalent pids
In case if pid1 is equal to pid2 the kcmp will return -EBUSY, which makes no sence. Make it able to work with equivalent pids. Selftest is extended as well.
Repored-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org> --- diff -u linux-2.6.git/kernel/kcmp.c linux-2.6.git/kernel/kcmp.c --- linux-2.6.git/kernel/kcmp.c +++ linux-2.6.git/kernel/kcmp.c @@ -58,22 +58,28 @@ return file; } -static void access_unlock(struct task_struct *task) +static void kcmp_unlock(struct mutex *m1, struct mutex *m2) { - mutex_unlock(&task->signal->cred_guard_mutex); + if (likely(m2 != m1)) + mutex_unlock(m2); + mutex_unlock(m1); } -static int access_trylock(struct task_struct *task) +static int kcmp_lock(struct mutex *m1, struct mutex *m2) { - if (!mutex_trylock(&task->signal->cred_guard_mutex)) - return -EBUSY; + int err; - if (!ptrace_may_access(task, PTRACE_MODE_READ)) { - mutex_unlock(&task->signal->cred_guard_mutex); - return -EPERM; + if (m2 > m1) + swap(m1, m2); + + err = mutex_lock_killable(m1); + if (!err && likely(m1 != m2)) { + err = mutex_lock_killable_nested(m2, SINGLE_DEPTH_NESTING); + if (err) + mutex_unlock(m1); } - return 0; + return err; } SYSCALL_DEFINE5(kcmp, pid_t, pid1, pid_t, pid2, int, type, @@ -100,12 +106,15 @@ /* * One should have enough rights to inspect task details. */ - ret = access_trylock(task1); + ret = kcmp_lock(&task1->signal->cred_guard_mutex, + &task2->signal->cred_guard_mutex); if (ret) goto err; - ret = access_trylock(task2); - if (ret) + if (!ptrace_may_access(task1, PTRACE_MODE_READ) || + !ptrace_may_access(task2, PTRACE_MODE_READ)) { + ret = -EPERM; goto err_unlock; + } switch (type) { case KCMP_FILE: { @@ -149,9 +158,9 @@ break; } - access_unlock(task2); err_unlock: - access_unlock(task1); + kcmp_unlock(&task1->signal->cred_guard_mutex, + &task2->signal->cred_guard_mutex); err: put_task_struct(task1); put_task_struct(task2); diff -u linux-2.6.git/tools/testing/selftests/kcmp/kcmp_test.c linux-2.6.git/tools/testing/selftests/kcmp/kcmp_test.c --- linux-2.6.git/tools/testing/selftests/kcmp/kcmp_test.c +++ linux-2.6.git/tools/testing/selftests/kcmp/kcmp_test.c @@ -74,6 +74,15 @@ ret = -1; } else printf("PASS: 0 returned as expected\n"); + + /* Compare with self */ + ret = sys_kcmp(pid1, pid1, KCMP_VM, 0, 0); + if (ret) { + printf("FAIL: 0 expected but %li returned\n", ret); + ret = -1; + } else + printf("PASS: 0 returned as expected\n"); + exit(ret); }
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