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authorRafael J. Wysocki <rafael.j.wysocki@intel.com>2018-12-03 13:04:18 +0100
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2018-12-04 16:04:20 +0100
commita72173ecfc6774cf2d55de9fb29421ce69e3428c (patch)
treea36bb49798f5f934e3a418ab3a7ab84076857346 /fs
parent2595646791c319cadfdbf271563aac97d0843dc7 (diff)
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Revert "exec: make de_thread() freezable"
Revert commit c22397888f1e "exec: make de_thread() freezable" as requested by Ingo Molnar: "So there's a new regression in v4.20-rc4, my desktop produces this lockdep splat: [ 1772.588771] WARNING: pkexec/4633 still has locks held! [ 1772.588773] 4.20.0-rc4-custom-00213-g93a49841322b #1 Not tainted [ 1772.588775] ------------------------------------ [ 1772.588776] 1 lock held by pkexec/4633: [ 1772.588778] #0: 00000000ed85fbf8 (&sig->cred_guard_mutex){+.+.}, at: prepare_bprm_creds+0x2a/0x70 [ 1772.588786] stack backtrace: [ 1772.588789] CPU: 7 PID: 4633 Comm: pkexec Not tainted 4.20.0-rc4-custom-00213-g93a49841322b #1 [ 1772.588792] Call Trace: [ 1772.588800] dump_stack+0x85/0xcb [ 1772.588803] flush_old_exec+0x116/0x890 [ 1772.588807] ? load_elf_phdrs+0x72/0xb0 [ 1772.588809] load_elf_binary+0x291/0x1620 [ 1772.588815] ? sched_clock+0x5/0x10 [ 1772.588817] ? search_binary_handler+0x6d/0x240 [ 1772.588820] search_binary_handler+0x80/0x240 [ 1772.588823] load_script+0x201/0x220 [ 1772.588825] search_binary_handler+0x80/0x240 [ 1772.588828] __do_execve_file.isra.32+0x7d2/0xa60 [ 1772.588832] ? strncpy_from_user+0x40/0x180 [ 1772.588835] __x64_sys_execve+0x34/0x40 [ 1772.588838] do_syscall_64+0x60/0x1c0 The warning gets triggered by an ancient lockdep check in the freezer: (gdb) list *0xffffffff812ece06 0xffffffff812ece06 is in flush_old_exec (./include/linux/freezer.h:57). 52 * DO NOT ADD ANY NEW CALLERS OF THIS FUNCTION 53 * If try_to_freeze causes a lockdep warning it means the caller may deadlock 54 */ 55 static inline bool try_to_freeze_unsafe(void) 56 { 57 might_sleep(); 58 if (likely(!freezing(current))) 59 return false; 60 return __refrigerator(false); 61 } I reviewed the ->cred_guard_mutex code, and the mutex is held across all of exec() - and we always did this. But there's this recent -rc4 commit: > Chanho Min (1): > exec: make de_thread() freezable c22397888f1e: exec: make de_thread() freezable I believe this commit is bogus, you cannot call try_to_freeze() from de_thread(), because it's holding the ->cred_guard_mutex." Reported-by: Ingo Molnar <mingo@kernel.org> Tested-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'fs')
-rw-r--r--fs/exec.c5
1 files changed, 2 insertions, 3 deletions
diff --git a/fs/exec.c b/fs/exec.c
index acc3a5536384..fc281b738a98 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -62,7 +62,6 @@
#include <linux/oom.h>
#include <linux/compat.h>
#include <linux/vmalloc.h>
-#include <linux/freezer.h>
#include <linux/uaccess.h>
#include <asm/mmu_context.h>
@@ -1084,7 +1083,7 @@ static int de_thread(struct task_struct *tsk)
while (sig->notify_count) {
__set_current_state(TASK_KILLABLE);
spin_unlock_irq(lock);
- freezable_schedule();
+ schedule();
if (unlikely(__fatal_signal_pending(tsk)))
goto killed;
spin_lock_irq(lock);
@@ -1112,7 +1111,7 @@ static int de_thread(struct task_struct *tsk)
__set_current_state(TASK_KILLABLE);
write_unlock_irq(&tasklist_lock);
cgroup_threadgroup_change_end(tsk);
- freezable_schedule();
+ schedule();
if (unlikely(__fatal_signal_pending(tsk)))
goto killed;
}