The patch titled
exec: simplify the new ->sighand allocation
has been added to the -mm tree. Its filename is
exec-simplify-the-new-sighand-allocation.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: exec: simplify the new ->sighand allocation
From: Oleg Nesterov <oleg@xxxxxxxxxx>
de_thread() pre-allocates newsighand to make sure that exec() can't fail after
killing all sub-threads. Imho, this buys nothing, but complicates the code:
- this is (mostly) needed to handle CLONE_SIGHAND without CLONE_THREAD
tasks, this is very unlikely (if ever used) case
- unless we already have some serious problems, GFP_KERNEL allocation
should not fail
- ENOMEM still can happen after de_thread(), ->sighand is not the last
object we have to allocate
Change the code to allocate the new ->sighand on demand.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Roland McGrath <roland@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/exec.c | 24 +++++++++---------------
1 files changed, 9 insertions(+), 15 deletions(-)
diff -puN fs/exec.c~exec-simplify-the-new-sighand-allocation fs/exec.c
--- a/fs/exec.c~exec-simplify-the-new-sighand-allocation
+++ a/fs/exec.c
@@ -747,7 +747,7 @@ static int exec_mmap(struct mm_struct *m
static int de_thread(struct task_struct *tsk)
{
struct signal_struct *sig = tsk->signal;
- struct sighand_struct *newsighand, *oldsighand = tsk->sighand;
+ struct sighand_struct *oldsighand = tsk->sighand;
spinlock_t *lock = &oldsighand->siglock;
struct task_struct *leader = NULL;
int count;
@@ -762,10 +762,6 @@ static int de_thread(struct task_struct
return 0;
}
- newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
- if (!newsighand)
- return -ENOMEM;
-
if (thread_group_empty(tsk))
goto no_thread_group;
@@ -782,7 +778,6 @@ static int de_thread(struct task_struct
*/
spin_unlock_irq(lock);
read_unlock(&tasklist_lock);
- kmem_cache_free(sighand_cachep, newsighand);
return -EAGAIN;
}
@@ -901,17 +896,16 @@ no_thread_group:
if (leader)
release_task(leader);
- if (atomic_read(&oldsighand->count) == 1) {
- /*
- * Now that we nuked the rest of the thread group,
- * it turns out we are not sharing sighand any more either.
- * So we can just keep it.
- */
- kmem_cache_free(sighand_cachep, newsighand);
- } else {
+ if (atomic_read(&oldsighand->count) != 1) {
+ struct sighand_struct *newsighand;
/*
- * Move our state over to newsighand and switch it in.
+ * This ->sighand is shared with the CLONE_SIGHAND
+ * but not CLONE_THREAD task, switch to the new one.
*/
+ newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
+ if (!newsighand)
+ return -ENOMEM;
+
atomic_set(&newsighand->count, 1);
memcpy(newsighand->action, oldsighand->action,
sizeof(newsighand->action));
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
origin.patch
posix-timers-fix-creation-race.patch
signalfd-fix-interaction-with-posix-timers.patch
signalfd-make-it-group-wide-fix-posix-timers-scheduling.patch
exec-kill-unsafe-bug_onsig-count-checks.patch
git-dvb.patch
rt-ptracer-can-monopolize-cpu-was-cpu-hotplug-and-real-time.patch
clone-flag-clone_parent_tidptr-leaves-invalid-results-in-memory.patch
do_sys_poll-simplify-playing-with-on-stack-data.patch
do_sys_poll-simplify-playing-with-on-stack-data-fix.patch
do_poll-return-eintr-when-signalled.patch
pi-futex-set-pf_exiting-without-taking-pi_lock.patch
do_sigaction-remove-now-unneeded-recalc_sigpending.patch
handle-the-multi-threaded-inits-exit-properly.patch
wait_task_zombie-remove-unneeded-child-signal-check.patch
wait_task_zombie-fix-2-3-races-vs-forget_original_parent.patch
exit_notify-dont-take-tasklist-for-tif_sigpending-re-targeting.patch
zap_other_threads-dont-optimize-thread_group_empty-case.patch
wait_task_zombie-dont-fight-with-non-existing-race-with-a-dying-ptracee.patch
__group_complete_signal-eliminate-unneeded-wakeup-of-group_exit_task.patch
use-erestart_restartblock-if-poll-is-interrupted-by-a-signal.patch
exec-simplify-sighand-switching.patch
exec-simplify-the-new-sighand-allocation.patch
exec-consolidate-2-fast-paths.patch
exec-rt-sub-thread-can-livelock-and-monopolize-cpu-on-exec.patch
cpu-hotplug-slab-cleanup-cpuup_callback.patch
cpu-hotplug-slab-fix-memory-leak-in-cpu-hotplug-error-path.patch
cpu-hotplug-cpu-deliver-cpu_up_canceled-only-to-notify_oked-callbacks-with-cpu_up_prepare.patch
cpu-hotplug-topology-remove-topology_dev_map.patch
cpu-hotplug-thermal_throttle-fix-cpu-hotplug-error-handling.patch
cpu-hotplug-msr-fix-cpu-hotplug-error-handling.patch
cpu-hotplug-cpuid-fix-cpu-hotplug-error-handling.patch
cpu-hotplug-mce-fix-cpu-hotplug-error-handling.patch
cpu-hotplug-intel_cacheinfo-fix-cpu-hotplug-error-handling.patch
cpu-hotplug-intel_cacheinfo-fix-cpu-hotplug-error-handling-fix-a-section-mismatch-warning.patch
make-access-to-tasks-nsproxy-lighter.patch
workqueue-debug-flushing-deadlocks-with-lockdep.patch
workqueue-debug-work-related-deadlocks-with-lockdep.patch
pid-namespaces-rework-forget_original_parent.patch
pid-namespaces-move-exit_task_namespaces.patch
pid-namespaces-introduce-ms_kernmount-flag.patch
pid-namespaces-prepare-proc_flust_task-to-flush-entries-from-multiple-proc-trees.patch
pid-namespaces-introduce-struct-upid.patch
pid-namespaces-add-support-for-pid-namespaces-hierarchy.patch
pid-namespaces-make-alloc_pid-free_pid-and-put_pid-work-with-struct-upid.patch
pid-namespaces-helpers-to-obtain-pid-numbers.patch
pid-namespaces-helpers-to-find-the-task-by-its-numerical-ids.patch
pid-namespaces-move-alloc_pid-lower-in-copy_process.patch
pid-namespaces-make-proc-have-multiple-superblocks-one-for-each-namespace.patch
pid-namespaces-miscelaneous-preparations-for-pid-namespaces.patch
pid-namespaces-allow-cloning-of-new-namespace.patch
pid-namespaces-allow-cloning-of-new-namespace-fix-check-for-return-value-of-create_pid_namespace.patch
pid-namespaces-make-proc_flush_task-actually-from-entries-from-multiple-namespaces.patch
pid-namespaces-initialize-the-namespaces-proc_mnt.patch
pid-namespaces-create-a-slab-cache-for-struct-pid_namespace.patch
pid-namespaces-allow-signalling-container-init.patch
pid-namespaces-destroy-pid-namespace-on-inits-death.patch
pid-namespaces-changes-to-show-virtual-ids-to-user.patch
pid-namespaces-changes-to-show-virtual-ids-to-user-fix-the-return-value-of-sys_set_tid_address.patch
pid-namespaces-changes-to-show-virtual-ids-to-user-use-find_task_by_pid_ns-in-places-that-operate-with-virtual.patch
pid-namespaces-remove-the-struct-pid-unneeded-fields.patch
isolate-some-explicit-usage-of-task-tgid.patch
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