The patch titled
signal: sigprocmask() should do retarget_shared_pending()
has been removed from the -mm tree. Its filename was
signal-sigprocmask-should-do-retarget_shared_pending.patch
This patch was dropped because an updated version will be merged
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: signal: sigprocmask() should do retarget_shared_pending()
From: Oleg Nesterov <oleg@xxxxxxxxxx>
In short, almost every changing of current->blocked is wrong, or at least
can lead to the unexpected results.
For example. Two threads T1 and T2, T1 sleeps in sigtimedwait/pause/etc.
kill(tgid, SIG) can pick T2 for TIF_SIGPENDING. If T2 calls sigprocmask()
and blocks SIG before it notices the pending signal, nobody else can
handle this pending shared signal.
I am not sure this is bug, but at least this looks strange imho. T1
should not sleep forever, there is a signal which should wake it up.
This patch moves the code which actually changes ->blocked into the new
helper, set_current_blocked() and changes this code to call
retarget_shared_pending() as exit_signals() does. We should only care
about the signals we just blocked, we use "newset & ~current->blocked" as
a mask.
We do not check !sigisemptyset(newblocked), retarget_shared_pending() is
cheap unless mask & shared_pending.
Note: for this particular case we could simply change sigprocmask() to
return -EINTR if signal_pending(), but then we should change other callers
and, more importantly, if we need this fix then set_current_blocked() will
have more callers and some of them can't restart. See the next patch as a
random example.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Acked-by: Tejun Heo <tj@xxxxxxxxxx>
Cc: "Nikita V. Youshchenko" <nyoushchenko@xxxxxxxxxx>
Reviewed-by: Matt Fleming <matt@xxxxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/signal.h | 1 +
kernel/signal.c | 21 ++++++++++++++++-----
2 files changed, 17 insertions(+), 5 deletions(-)
diff -puN include/linux/signal.h~signal-sigprocmask-should-do-retarget_shared_pending include/linux/signal.h
--- a/include/linux/signal.h~signal-sigprocmask-should-do-retarget_shared_pending
+++ a/include/linux/signal.h
@@ -243,6 +243,7 @@ extern long do_rt_tgsigqueueinfo(pid_t t
siginfo_t *info);
extern long do_sigpending(void __user *, unsigned long);
extern int sigprocmask(int, sigset_t *, sigset_t *);
+extern void set_current_blocked(const sigset_t *);
extern int show_unhandled_signals;
struct pt_regs;
diff -puN kernel/signal.c~signal-sigprocmask-should-do-retarget_shared_pending kernel/signal.c
--- a/kernel/signal.c~signal-sigprocmask-should-do-retarget_shared_pending
+++ a/kernel/signal.c
@@ -2298,6 +2298,21 @@ long do_no_restart_syscall(struct restar
return -EINTR;
}
+void set_current_blocked(const sigset_t *newset)
+{
+ struct task_struct *tsk = current;
+
+ spin_lock_irq(&tsk->sighand->siglock);
+ if (signal_pending(tsk) && !thread_group_empty(tsk)) {
+ sigset_t newblocked;
+ signandsets(&newblocked, newset, ¤t->blocked);
+ retarget_shared_pending(tsk, &newblocked);
+ }
+ tsk->blocked = *newset;
+ recalc_sigpending();
+ spin_unlock_irq(&tsk->sighand->siglock);
+}
+
/*
* This is also useful for kernel threads that want to temporarily
* (or permanently) block certain signals.
@@ -2329,11 +2344,7 @@ int sigprocmask(int how, sigset_t *set,
return -EINVAL;
}
- spin_lock_irq(&tsk->sighand->siglock);
- tsk->blocked = newset;
- recalc_sigpending();
- spin_unlock_irq(&tsk->sighand->siglock);
-
+ set_current_blocked(&newset);
return 0;
}
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
linux-next.patch
ptrace-fix-signal-wait_chldexit-usage-in-task_clear_group_stop_trapping.patch
cgroups-read-write-lock-clone_thread-forking-per-threadgroup.patch
cgroups-add-per-thread-subsystem-callbacks.patch
cgroups-make-procs-file-writable.patch
cgroups-use-flex_array-in-attach_proc.patch
asm-generic-ptraceh-start-a-common-low-level-ptrace-helper.patch
blackfin-convert-to-asm-generic-ptraceh.patch
x86-convert-to-asm-generic-ptraceh.patch
sh-convert-to-asm-generic-ptraceh.patch
kgdbts-unify-generalize-gdb-breakpoint-adjustment.patch
x86-signal-handle_signal-should-use-set_current_blocked.patch
x86-signal-sys_rt_sigreturn-should-use-set_current_blocked.patch
signal-cleanup-sys_rt_sigprocmask.patch
fs-execc-provide-the-correct-process-pid-to-the-pipe-helper.patch
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