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Message-Id: <1361008406-2307-5-git-send-email-msb@chromium.org>
Date: Sat, 16 Feb 2013 01:53:26 -0800
From: Mandeep Singh Baines <msb@...omium.org>
To: linux-kernel@...r.kernel.org
Cc: Ben Chan <benchan@...omium.org>,
Mandeep Singh Baines <msb@...omium.org>,
Oleg Nesterov <oleg@...hat.com>, Tejun Heo <tj@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
"Rafael J. Wysocki" <rjw@...k.pl>, Ingo Molnar <mingo@...hat.com>
Subject: [PATCH 5/5] coredump: ignore non-fatal signals when core dumping to a pipe
From: Ben Chan <benchan@...omium.org>
Make wait_for_dump_helpers() not abort piping the core dump data when the
crashing process has received a non-fatal signal. The abort still occurs
in the case of SIGKILL.
Testing:
localhost ~ # echo "|/usr/bin/sleep 1d" > /proc/sys/kernel/core_pattern
localhost ~ # sleep 1d &
[1] 2514
localhost ~ # kill -ABRT $! # Cause coredump
localhost ~ # kill -USR1 $! # Send non-fatal signal
localhost ~ # top -p $! -n1 -b # Verify that we aren't dead or busy waiting
top - 16:45:34 up 2 min, 0 users, load average: 0.71, 0.42, 0.17
Tasks: 1 total, 0 running, 1 sleeping, 0 stopped, 0 zombie
Cpu(s): 26.0%us, 8.5%sy, 0.0%ni, 65.1%id, 0.2%wa, 0.0%hi, 0.1%si, 0.0%st
Mem: 991516k total, 418556k used, 572960k free, 5948k buffers
Swap: 0k total, 0k used, 0k free, 289928k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
2514 root 20 0 1868 392 336 S 0 0.0 0:00.00 sleep
localhost ~ # echo mem > /sys/power/state # Suspend
localhost ~ # top -p $! -n1 -b # Verify that we aren't dead or busy waiting
top - 16:46:46 up 3 min, 0 users, load average: 1.68, 0.69, 0.28
Tasks: 1 total, 0 running, 1 sleeping, 0 stopped, 0 zombie
Cpu(s): 24.1%us, 7.7%sy, 0.0%ni, 67.9%id, 0.2%wa, 0.0%hi, 0.1%si, 0.0%st
Mem: 991516k total, 419956k used, 571560k free, 5996k buffers
Swap: 0k total, 0k used, 0k free, 290208k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
2514 root 20 0 1868 392 336 S 0 0.0 0:00.00 sleep
localhost ~ # kill -KILL $!
[1]+ Aborted (core dumped) sleep 1d
Addresses http://crosbug.com/21559
Changes since v1:
* Mandeep Singh Baines
* To prevent blocking suspend, add try_to_freeze().
Changes since v2:
* LKML: <20130215150117.GB30829@...hat.com> Oleg Nestorov
* Block non-fatal signals to avoid poll_wait busy waiting.
* LKML: <20130215152538.9a61a44e.akpm@...ux-foundation.org> Andrew Morton
* Added comment re: try_to_freeze and clarified commit message.
Changes since v3:
* Mandeep Singh Baines
* Clear signal pending caused by fake signal from freeze_task().
* Document how the patch was tested.
Changes since v4:
* Mandeep Singh Baines
* Moved clearing of fake signal to __refrigerator() (separate patch).
* SIGKILL will remain in shared_pending since SIGNAL_GROUP_EXIT is set,
so fatal_signal_pending() will return false. Add a sigkill_pending()
helper that does the right thing.
Signed-off-by: Ben Chan <benchan@...omium.org>
Signed-off-by: Mandeep Singh Baines <msb@...omium.org>
CC: Oleg Nesterov <oleg@...hat.com>
CC: Tejun Heo <tj@...nel.org>
CC: Andrew Morton <akpm@...ux-foundation.org>
CC: Rafael J. Wysocki <rjw@...k.pl>
CC: Ingo Molnar <mingo@...hat.com>
---
fs/coredump.c | 25 ++++++++++++++++++++++++-
1 file changed, 24 insertions(+), 1 deletion(-)
diff --git a/fs/coredump.c b/fs/coredump.c
index 1774932..3eb799d 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -32,6 +32,7 @@
#include <linux/pipe_fs_i.h>
#include <linux/oom.h>
#include <linux/compat.h>
+#include <linux/freezer.h>
#include <asm/uaccess.h>
#include <asm/mmu_context.h>
@@ -407,9 +408,21 @@ static void coredump_finish(struct mm_struct *mm)
mm->core_state = NULL;
}
+static int sigkill_pending(struct task_struct *tsk)
+{
+ return signal_pending(tsk) &&
+ (sigismember(&tsk->pending.signal, SIGKILL) ||
+ sigismember(&tsk->signal->shared_pending.signal, SIGKILL));
+}
+
static void wait_for_dump_helpers(struct file *file)
{
struct pipe_inode_info *pipe;
+ sigset_t blocked, previous;
+
+ /* Block all but fatal signals. */
+ siginitsetinv(&blocked, sigmask(SIGKILL));
+ sigprocmask(SIG_BLOCK, &blocked, &previous);
pipe = file->f_path.dentry->d_inode->i_pipe;
@@ -417,16 +430,26 @@ static void wait_for_dump_helpers(struct file *file)
pipe->readers++;
pipe->writers--;
- while ((pipe->readers > 1) && (!signal_pending(current))) {
+ while ((pipe->readers > 1) && (!sigkill_pending(current))) {
wake_up_interruptible_sync(&pipe->wait);
kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
pipe_wait(pipe);
+
+ /*
+ * Non-fatal signals are blocked. So we need to try
+ * to freeze in order to not block suspend.
+ */
+ pipe_unlock(pipe);
+ try_to_freeze();
+ pipe_lock(pipe);
}
pipe->readers--;
pipe->writers++;
pipe_unlock(pipe);
+ /* Restore signals. */
+ sigprocmask(SIG_SETMASK, &previous, NULL);
}
/*
--
1.7.12.4
--
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