diff options
Diffstat (limited to 'winsup/cygwin/spawn.cc')
-rw-r--r-- | winsup/cygwin/spawn.cc | 58 |
1 files changed, 42 insertions, 16 deletions
diff --git a/winsup/cygwin/spawn.cc b/winsup/cygwin/spawn.cc index b42e450c2..f052d350b 100644 --- a/winsup/cygwin/spawn.cc +++ b/winsup/cygwin/spawn.cc @@ -455,23 +455,49 @@ child_info_spawn::worker (const char *prog_arg, const char *const *argv, c_flags |= CREATE_SEPARATE_WOW_VDM | CREATE_UNICODE_ENVIRONMENT; - /* We're adding the CREATE_BREAKAWAY_FROM_JOB flag here to workaround issues - with the "Program Compatibility Assistant (PCA) Service" observed on - Windows 7. For some reason, when starting long running sessions from - mintty, the affected svchost.exe process takes more and more memory and - at one point takes over the CPU. At this point the machine becomes - unresponsive. The only way to get back to normal is to stop the entire - mintty session, or to stop the PCA service. However, a process which - is controlled by PCA is part of a compatibility job, which allows child - processes to break away from the job. This helps to avoid this issue. */ - JOBOBJECT_BASIC_LIMIT_INFORMATION jobinfo; - if (QueryInformationJobObject (NULL, JobObjectBasicLimitInformation, - &jobinfo, sizeof jobinfo, NULL) - && (jobinfo.LimitFlags & (JOB_OBJECT_LIMIT_BREAKAWAY_OK - | JOB_OBJECT_LIMIT_SILENT_BREAKAWAY_OK))) + if (wincap.has_program_compatibility_assitant ()) { - debug_printf ("Add CREATE_BREAKAWAY_FROM_JOB"); - c_flags |= CREATE_BREAKAWAY_FROM_JOB; + /* We're adding the CREATE_BREAKAWAY_FROM_JOB flag here to workaround + issues with the "Program Compatibility Assistant (PCA) Service" + starting with Windows Vista. For some reason, when starting long + running sessions from mintty(*), the affected svchost.exe process + takes more and more memory and at one point takes over the CPU. At + this point the machine becomes unresponsive. The only way to get + back to normal is to stop the entire mintty session, or to stop the + PCA service. However, a process which is controlled by PCA is part + of a compatibility job, which allows child processes to break away + from the job. This helps to avoid this issue. + + (*) Note that this is not mintty's fault. It has just been observed + with mintty in the first place. See the archives for more info: + http://cygwin.com/ml/cygwin-developers/2012-02/msg00018.html */ + + JOBOBJECT_BASIC_LIMIT_INFORMATION jobinfo; + + /* Calling QueryInformationJobObject costs time. Starting with + Windows XP there's a function IsProcessInJob, which fetches the + information whether or not we're part of a job 20 times faster than + the call to QueryInformationJobObject. But we're still + supporting Windows 2000, so we can't just link to that function. + On the other hand, loading the function pointer at runtime is a + time comsuming operation, too. So, what we do here is to emulate + the IsProcessInJob function when called for the own process and with + a NULL job handle. In this case it just returns the value of the + lowest bit from PEB->EnvironmentUpdateCount (observed with WinDbg). + The name of this PEB member is the same in all (inofficial) + documentations of the PEB. Apparently it's a bit misleading. + As a result, we only call QueryInformationJobObject if we're on + Vista or later *and* if the PEB indicates we're running in a job. + Tested on Vista/32, Vista/64, W7/32, W7/64, W8/64. */ + if ((NtCurrentTeb ()->Peb->EnvironmentUpdateCount & 1) != 0 + && QueryInformationJobObject (NULL, JobObjectBasicLimitInformation, + &jobinfo, sizeof jobinfo, NULL) + && (jobinfo.LimitFlags & (JOB_OBJECT_LIMIT_BREAKAWAY_OK + | JOB_OBJECT_LIMIT_SILENT_BREAKAWAY_OK))) + { + debug_printf ("Add CREATE_BREAKAWAY_FROM_JOB"); + c_flags |= CREATE_BREAKAWAY_FROM_JOB; + } } if (mode == _P_DETACH) |