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nptl: Move cancel state out of cancelhandling

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Now that thread cancellation state is not accessed concurrently anymore,
it is possible to move it out the 'cancelhandling'.

The code is also simplified: CANCELLATION_P is replaced with a
internal pthread_testcancel call and the CANCELSTATE_BIT{MASK} is
removed.

With this behavior pthread_setcancelstate does not require to act on
cancellation if cancel type is asynchronous (is already handled either
by pthread_setcanceltype or by the signal handler).

Checked on x86_64-linux-gnu and aarch64-linux-gnu.
This commit is contained in:
Adhemerval Zanella 2020-03-31 15:43:25 -03:00
parent 26cfbb7162
commit 2b51742531
14 changed files with 34 additions and 63 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
manual/pattern.texi
View File

@ -1820,7 +1820,6 @@ the beginning of the vector.
@c (disable cancellation around exec_comm; it may do_cancel the
@c second time, if async cancel is enabled)
@c THREAD_ATOMIC_CMPXCHG_VAL dup ok
@c CANCEL_ENABLED_AND_CANCELED_AND_ASYNCHRONOUS dup ok
@c do_cancel @ascuplugin @ascuheap @acsmem
@c THREAD_ATOMIC_BIT_SET dup ok
@c pthread_unwind @ascuplugin @ascuheap @acsmem

3
manual/process.texi
View File

@ -68,7 +68,7 @@ until the subprogram terminates before you can do anything else.
@c CLEANUP_HANDLER @ascuplugin @ascuheap @acsmem
@c libc_cleanup_region_start @ascuplugin @ascuheap @acsmem
@c pthread_cleanup_push_defer @ascuplugin @ascuheap @acsmem
@c CANCELLATION_P @ascuplugin @ascuheap @acsmem
@c __pthread_testcancel @ascuplugin @ascuheap @acsmem
@c CANCEL_ENABLED_AND_CANCELED ok
@c do_cancel @ascuplugin @ascuheap @acsmem
@c cancel_handler ok
@ -86,7 +86,6 @@ until the subprogram terminates before you can do anything else.
@c SINGLE_THREAD_P ok
@c LIBC_CANCEL_ASYNC @ascuplugin @ascuheap @acsmem
@c libc_enable_asynccancel @ascuplugin @ascuheap @acsmem
@c CANCEL_ENABLED_AND_CANCELED_AND_ASYNCHRONOUS dup ok
@c do_cancel dup @ascuplugin @ascuheap @acsmem
@c LIBC_CANCEL_RESET ok
@c libc_disable_asynccancel ok

1
nptl/allocatestack.c
View File

@ -160,6 +160,7 @@ get_cached_stack (size_t *sizep, void **memp)
/* Cancellation handling is back to the default. */
result->cancelhandling = 0;
result->cancelstate = PTHREAD_CANCEL_ENABLE;
result->cleanup = NULL;
result->setup_failed = 0;

3
nptl/cancellation.c
View File

@ -44,7 +44,8 @@ __pthread_enable_asynccancel (void)
oldval);
if (__glibc_likely (curval == oldval))
{
if (CANCEL_ENABLED_AND_CANCELED_AND_ASYNCHRONOUS (newval))
if (self->cancelstate == PTHREAD_CANCEL_ENABLE
&& CANCEL_CANCELED_AND_ASYNCHRONOUS (newval))
{
THREAD_SETMEM (self, result, PTHREAD_CANCELED);
__do_cancel ();

2
nptl/cleanup_defer.c
View File

@ -92,7 +92,7 @@ ___pthread_unregister_cancel_restore (__pthread_unwind_buf_t *buf)
cancelhandling = curval;
}
CANCELLATION_P (self);
__pthread_testcancel ();
}
}
versioned_symbol (libc, ___pthread_unregister_cancel_restore,

14
nptl/descr.h
View File

@ -277,9 +277,6 @@ struct pthread
/* Flags determining processing of cancellation. */
int cancelhandling;
/* Bit set if cancellation is disabled. */
#define CANCELSTATE_BIT 0
#define CANCELSTATE_BITMASK (0x01 << CANCELSTATE_BIT)
/* Bit set if asynchronous cancellation mode is selected. */
#define CANCELTYPE_BIT 1
#define CANCELTYPE_BITMASK (0x01 << CANCELTYPE_BIT)
@ -298,11 +295,8 @@ struct pthread
/* Mask for the rest. Helps the compiler to optimize. */
#define CANCEL_RESTMASK 0xffffff80
#define CANCEL_ENABLED_AND_CANCELED(value) \
(((value) & (CANCELSTATE_BITMASK | CANCELED_BITMASK | EXITING_BITMASK \
| CANCEL_RESTMASK | TERMINATED_BITMASK)) == CANCELED_BITMASK)
#define CANCEL_ENABLED_AND_CANCELED_AND_ASYNCHRONOUS(value) \
(((value) & (CANCELSTATE_BITMASK | CANCELTYPE_BITMASK | CANCELED_BITMASK \
#define CANCEL_CANCELED_AND_ASYNCHRONOUS(value) \
(((value) & (CANCELTYPE_BITMASK | CANCELED_BITMASK \
| EXITING_BITMASK | CANCEL_RESTMASK | TERMINATED_BITMASK)) \
== (CANCELTYPE_BITMASK | CANCELED_BITMASK))
@ -404,6 +398,10 @@ struct pthread
/* Indicates whether is a C11 thread created by thrd_creat. */
bool c11;
/* Thread cancel state (PTHREAD_CANCEL_ENABLE or
PTHREAD_CANCEL_DISABLE). */
unsigned char cancelstate;
/* Used on strsignal. */
struct tls_internal_t tls_state;

2
nptl/libc-cleanup.c
View File

@ -79,7 +79,7 @@ __libc_cleanup_pop_restore (struct _pthread_cleanup_buffer *buffer)
cancelhandling = curval;
}
CANCELLATION_P (self);
__pthread_testcancel ();
}
}
libc_hidden_def (__libc_cleanup_pop_restore)

12
nptl/pthreadP.h
View File

@ -245,18 +245,6 @@ libc_hidden_proto (__pthread_current_priority)
#define INVALID_TD_P(pd) __builtin_expect ((pd)->tid <= 0, 0)
#define INVALID_NOT_TERMINATED_TD_P(pd) __builtin_expect ((pd)->tid < 0, 0)
/* Cancellation test. */
#define CANCELLATION_P(self) \
do { \
int cancelhandling = THREAD_GETMEM (self, cancelhandling); \
if (CANCEL_ENABLED_AND_CANCELED (cancelhandling)) \
{ \
THREAD_SETMEM (self, result, PTHREAD_CANCELED); \
__do_cancel (); \
} \
} while (0)
extern void __pthread_unwind (__pthread_unwind_buf_t *__buf)
__cleanup_fct_attribute __attribute ((__noreturn__))
#if !defined SHARED && !IS_IN (libpthread)

2
nptl/pthread_cancel.c
View File

@ -45,7 +45,7 @@ sigcancel_handler (int sig, siginfo_t *si, void *ctx)
int ch = atomic_load_relaxed (&self->cancelhandling);
/* Cancelation not enabled, not cancelled, or already exitting. */
if ((ch & CANCELSTATE_BITMASK) != 0
if (self->cancelstate == PTHREAD_CANCEL_DISABLE
|| (ch & CANCELED_BITMASK) == 0
|| (ch & EXITING_BITMASK) != 0)
return;

5
nptl/pthread_join_common.c
View File

@ -59,7 +59,10 @@ __pthread_clockjoin_ex (pthread_t threadid, void **thread_return,
&& (pd->cancelhandling
& (CANCELED_BITMASK | EXITING_BITMASK
| TERMINATED_BITMASK)) == 0))
&& !CANCEL_ENABLED_AND_CANCELED (self->cancelhandling))
&& !(self->cancelstate == PTHREAD_CANCEL_ENABLE
&& (pd->cancelhandling & (CANCELED_BITMASK | EXITING_BITMASK
| TERMINATED_BITMASK))
== CANCELED_BITMASK))
/* This is a deadlock situation. The threads are waiting for each
other to finish. Note that this is a "may" error. To be 100%
sure we catch this error we would have to lock the data

36
nptl/pthread_setcancelstate.c
View File

@ -31,39 +31,9 @@ __pthread_setcancelstate (int state, int *oldstate)
self = THREAD_SELF;
int oldval = THREAD_GETMEM (self, cancelhandling);
while (1)
{
int newval = (state == PTHREAD_CANCEL_DISABLE
? oldval | CANCELSTATE_BITMASK
: oldval & ~CANCELSTATE_BITMASK);
/* Store the old value. */
if (oldstate != NULL)
*oldstate = ((oldval & CANCELSTATE_BITMASK)
? PTHREAD_CANCEL_DISABLE : PTHREAD_CANCEL_ENABLE);
/* Avoid doing unnecessary work. The atomic operation can
potentially be expensive if the memory has to be locked and
remote cache lines have to be invalidated. */
if (oldval == newval)
break;
/* Update the cancel handling word. This has to be done
atomically since other bits could be modified as well. */
int curval = THREAD_ATOMIC_CMPXCHG_VAL (self, cancelhandling, newval,
oldval);
if (__glibc_likely (curval == oldval))
{
if (CANCEL_ENABLED_AND_CANCELED_AND_ASYNCHRONOUS (newval))
__do_cancel ();
break;
}
/* Prepare for the next round. */
oldval = curval;
}
if (oldstate != NULL)
*oldstate = self->cancelstate;
self->cancelstate = state;
return 0;
}

3
nptl/pthread_setcanceltype.c
View File

@ -53,7 +53,8 @@ __pthread_setcanceltype (int type, int *oldtype)
oldval);
if (__glibc_likely (curval == oldval))
{
if (CANCEL_ENABLED_AND_CANCELED_AND_ASYNCHRONOUS (newval))
if (self->cancelstate == PTHREAD_CANCEL_ENABLE
&& CANCEL_CANCELED_AND_ASYNCHRONOUS (newval))
{
THREAD_SETMEM (self, result, PTHREAD_CANCELED);
__do_cancel ();

11
nptl/pthread_testcancel.c
View File

@ -23,7 +23,16 @@
void
___pthread_testcancel (void)
{
CANCELLATION_P (THREAD_SELF);
struct pthread *self = THREAD_SELF;
int cancelhandling = THREAD_GETMEM (self, cancelhandling);
if (self->cancelstate == PTHREAD_CANCEL_ENABLE
&& (cancelhandling & CANCELED_BITMASK)
&& !(cancelhandling & EXITING_BITMASK)
&& !(cancelhandling & TERMINATED_BITMASK))
{
THREAD_SETMEM (self, result, PTHREAD_CANCELED);
__do_cancel ();
}
}
versioned_symbol (libc, ___pthread_testcancel, pthread_testcancel, GLIBC_2_34);
versioned_symbol (libc, ___pthread_testcancel, __pthread_testcancel,

2
sysdeps/nptl/dl-tls_init_tp.c
View File

@ -94,4 +94,6 @@ __tls_init_tp (void)
It will be bigger than it actually is, but for unwind.c/pt-longjmp.c
purposes this is good enough. */
THREAD_SETMEM (pd, stackblock_size, (size_t) __libc_stack_end);
THREAD_SETMEM (pd, cancelstate, PTHREAD_CANCEL_ENABLE);
}